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5 Best Important Database Concepts for the Software Engineer

If you have this guide at hand at all times, you don’t need to distract your database experts every time a data need arises during a software development process.

Software engineering jobs are a good fit for people capable of dealing with diverse concepts. These concepts range from requirements analysis, team leadership, project management, scripting languages, testing techniques, to continuous integration, just to name a few. Then, there are a bunch of important database concepts for a software engineer to know: normalization, denormalization, SQL, No-SQL, ERDs, query optimization, etc. The list goes on!

In short, software engineering is for those who can do a little bit of everything while paying a lot of attention and care to each task. If you are one of those people, congratulations! You have a great career full of interesting challenges ahead of you.

I am a connoisseur of the database universe with experience on several software development teams. Let me guide you through the most important database concepts for a software engineer.

If you like checklists – if you are or expect to be a software engineer, you should like them – let's start by looking at a quick checklist of the database concepts you need to know:

  • Database design
  • SQL language
  • Relational database queries and optimization
  • Transactions
  • Object-relational mapping

We will analyze these in depth below.

Of course, there are more besides the ones included in this shortlist. To get a full view, read this article about the BEST ONLINE RESOURCES FOR LEARNING SQL AND DATABASE CONCEPTS.

Database Design

Part of a software engineer’s job is to make sure all deliverables passed from one member of the development team to another meet their objectives. For example, a requirements analysis should be clear, concise, and complete. A use case should contain all the information necessary for a coder to implement it. A piece of source code must fulfill the function explained in the use case. A test report should accurately describe all the defects found during a test run.

Also, a data model needs to fit a set of requirements and serve for generating a database with good performance and data integrity. Normally, software engineers do not spend time creating data models on their own. But they need to be able to sit down with a data modeler and analyze a model. They also need to determine if the model is well done. That is why ERD knowledge stays among the most critical database concepts for a software engineer.

How to Look at an ERD

Entity-relationship diagrams (ERDs) provide a graphical representation of the relationships between the objects that make up a data model. Data modelers use them primarily as tools to DOCUMENT AND COMMUNICATE DESIGN DECISIONS. As a software engineer, you should, at a minimum, be able to read an ERD, understand its logic, know what it represents, and determine if it correctly reflects the requirements of the software product being developed.

Having all that information, you can ask the data modelers the reasons for their design decisions and verify if those decisions are the right ones. You also need to detect, by looking at an ERD, if the database designer has misinterpreted a requirement or introduced an error in the data model that may lead to a serious bug in the software.

Concepts related to the interpretation of an ERD you should understand are the cardinality of relationships (one-to-one, one-to-many, or many-to-many), the choice of primary keys, the meaning of certain schema structures such as parent-child relationships, and common data warehousing schema types.

5 Important Database Concepts for the Software Engineer

As a software engineer, you should be able to read almost any ERD and understand what it means.

ERDs are presented at three different levels: conceptual, logical, and physical. It is usually sufficient for the software engineer to be able to read and understand the conceptual and logical models since the physical models are derived from them, only adding information necessary to implement the model in a particular database system.

On the other hand, with the aid of an intelligent data modeling tool such as VERTABELO, the physical diagrams can be generated automatically from the logical diagrams with complete confidence they are error-free. For this reason, a software engineer usually does not need to worry about reviewing physical diagrams.

One important thing every software engineer needs to be able to see in an ERD is whether the database schema is normalized and whether it needs to be. This brings us to the next item on our checklist.

Normalization and Denormalization

In transactional databases, normalization ensures database insert/update/delete operations do not produce anomalies or compromise the quality and integrity of the information. For identifying whether a design is normalized, important database concepts for a software engineer include primary keys, foreign keys, attribute dependencies, and surrogate keys.

An example of the problems associated with a non-normalized database is the potential anomalies that may appear in an e-commerce application. Such problems include the same product appearing twice in a sales report with two different names as if they were two different products.

In addition to avoiding these anomalies, normalization eliminates redundancies, which in turn reduces the storage space required by a database and improves query speed.

There are many normal forms, each one with its set of conditions. But you don’t need to memorize all of them. You can always read a guide on HOW TO REMEMBER DATABASE NORMAL FORMS. Most of the time, it’s sufficient to create schemas that comply with just the SECOND AND THIRD NORMAL FORMS.

In databases intended for analytical processing rather than transactional processing, you may need to make concessions to normalization so that you improve the performance of certain queries. These concessions are known as DENORMALIZATION TECHNIQUES. They usually involve adding some redundant attributes to avoid an excess of lookup tables. This helps deal with queries that add complexity and cost (in time and processing resources) for their resolution by the database engine.

Denormalization techniques are used only in schemas where data update is carried out by automatic or controlled processes. This is to avoid the risk of anomalies due to arbitrary information updates.

The SQL Language

Every software engineer needs to have a basic knowledge of SQL (Structured Query Language) for querying databases or for creating or modifying tables, indexes, views, or even a stored procedure or a trigger when needed. This knowledge allows you to perform some basic database tasks without taking time away from a DBA or database programmer.

A thorough knowledge of SQL concepts for a software engineer is probably not necessary. But you should have at least a full understanding of the SELECT command with its many clauses. It is especially important to understand the usefulness of JOIN clauses with all their variants – LEFT, RIGHT, INNER, and FULL – and the differences among them.

5 Important Database Concepts for the Software Engineer

Set theory may be helpful to better understand SQL JOINs.

To make good use of the database engine for writing efficient queries, you need to grasp the logic behind the relationships between the tables in an ERD. This helps you write the JOINs correctly in queries that include multiple tables. As a basic rule of thumb, fields involved in foreign key relationships between two tables are usually best suited for JOINs between them in a SELECT. For example, in the following ERD, you see the tables PAINTINGS and BUYERS are linked by the fields BUYER_NAME in PAINTINGS and NAME in BUYERS.

5 Important Database Concepts for the Software Engineer

You may want to use the fields involved in a foreign key relationship to JOIN tables in a SELECT statement.

This gives you the reassurance that your query results in good performance if you use the fields involved in a foreign key relation to join both tables in a SELECT.

SQL commands are subdivided into groups according to their functionality. The SELECT command with all its clauses forms a group in itself called DQL (Data Query Language).

There are two other commonly used groups of commands. DML (Data Manipulation Language) is used to insert, delete, or update rows in tables. DDL (Data Definition Language) is used to alter the structure of objects in a database. Examples where DDL is used include creating new tables, creating new fields in a table, and creating a view.

Query Optimization

Software engineers have too many things to do on a day-to-day basis for making performance improvement of a query a priority. Ideally, they should delegate this task to a SQL programmer, a DBA, a data modeler, or better yet, all of them together.

But even so, it is good to know what optimizing a query consists of, and in particular, how the creation of an index sometimes reduces the time a query takes to execute from hours to seconds. It is also good to be able to assess whether a DBA is telling the truth or just wants to avoid the task when he/she tells you a query cannot be optimized any more.

Query analysis tools allow you to “get inside the head” of an RDBMS to know what logic it applies when resolving a query. Query analysis breaks down each step required to get the data for that query and the cost in microseconds for each of those steps.

Optimizing a query often consists of finding the most time-consuming steps in the query execution plan and creating indexes to speed them up. You can read all about the VERY BASICS OF INDEX CREATION and solve some basic database performance problems yourself.

When you analyze a query execution strategy applied by an RDBMS, pay special attention to the steps that require the most work from the RDBMS. These include traversal of all the records in a table (called full table scan) or sequential traversal of the entries in an index (index scan).

A normalized database facilitates query optimization, as it does many other aspects of regular database use. This is yet another reason to spend time ensuring the data models are normalized.

Transactions

When an application sends data to a database, it commonly sends a sequence of insert, update, and delete operations. For example, recording data for an invoice may involve inserting rows in some tables, updating rows in others, and perhaps deleting rows in others.

All of these operations must be completed in their entirety or not run at all. If an error interrupts the sequence of these operations and it fails while executing, the information in the database can become inconsistent. This causes all sorts of data errors.

Transactions avoid this problem by preventing a sequence of interrelated operations from being partially executed. When a transaction is started, any error in the middle of the sequence causes the database to roll back to the time before the start of the sequence, leaving the data as it was before.

It is the responsibility of back-end programmers to open a transaction each time they start a sequence of interrelated write operations and close that transaction when finished.

Transactions must lock the tables they use to ensure the atomicity of a sequence of operations. One sequence should not collide with another that uses the same tables. A part of the database engine, called the transaction coordinator, acts as a traffic manager and instructs transactions to wait until another transaction using the same tables finishes.

The wait may be very long if a transaction takes too long to execute. Programmers must design their code intelligently to make transactions as fast as possible. This, of course, depends on the data model being correct and properly normalized (I cannot stress enough the model must be normalized). It is also vital that all tables involved in a transaction have indexes that minimize transaction time thus making the job easier for the database engine.

Another strategy to help avoid concurrent transaction problems applies particularly to data maintenance of master tables. If it is left to the users’ discretion to update, for example, the product or customer tables at any time, this may lead to deadlocks on these tables that prevent normal order entry. The correct strategy for these cases is to have a staging scheme for master data, from which the information is periodically and massively dumped to the production database on scheduled days or times.

Object-Relational Mapping

Object-relational mapping is a common area of work for backend programmers and database designers. As a software engineer, you need to know how work is done there and decide what part is for the database designer and what is for the back-end programmer.

Some examples of popular ORMs are Entity Framework, Hibernate, Django, and SQL Alchemy. Each of these depend on the programming language (e.g., Python, Java, C#) or the framework used to program the backend of an application.

ORMs make the logic of an application independent of the particularities of a database engine. This is particularly useful when it is known in advance an application must work (without adaptations) with different database engines.

This feature is very attractive for the backend programmer since it avoids the need to know the implementation details of a database. For the database designer, ORMs are not as appealing since they take away visibility into how the application interacts with the database.

As a software engineer, it is often your responsibility to arbitrate between these two opposing forces. Database designers want to resolve all the interactions between the application and the database with views, stored procedures, triggers, SQL scripts, jobs, and other tools of their choice. Backend programmers, on the other hand, want database designers to limit themselves to defining tables and indexes. They want everything else to be solved without leaving the realm of the source code in which they live.

It’s hard for me as a database designer to be impartial. But as a software engineer, you must be impartial and apply the right criteria to determine when ORMs are a solution and when they are a problem.

As I have said, ORMs seek to have all the logic of an application defined in the source code. In addition to decoupling the application from the database engine, the ORM ensures that a change in the application logic affects only the source code. If the application is installed in many places, upgrading it is simply a matter of distributing the new version to all these places, which can even be done automatically and at a minimal cost.

If, on the other hand, the application logic is implemented in database objects, upgrading the application to a new version may be very risky if it is installed in many places. No matter how careful you are in generating the upgrade scripts, you never know for sure what effect it has on the databases. Some data may cause an upgrade script to fail, and you have to spend time analyzing and resolving the failure, upgrade the application manually, then make sure the failed upgrade has not damaged the data.

If the application and the database are both installed in a single location and the version upgrade is done by deploying to that single location, the situation changes radically. In that case, it does not matter how many tables, views, stored procedures, or functions you have to update in the database. You can generate scripts and test them thoroughly until you are absolutely sure they work in the production database without causing any failure.

Not using ORMs has another advantage: it allows you to use all kinds of database engine tools to optimize performance and to debug database operations. This greatly reduces the costs and efforts required for application and database maintenance.

These Are Important Database Concepts for a Software Engineer, but Avoid Micromanagement

We’ve now seen all the important database concepts for a software engineer to master. Ideally, the engineer never needs to use this knowledge on a day-to-day basis for the development team to perform at its best and operate in a healthy climate. There may be exceptions in some cases, such as when the SQL programmer, the DBA, or the data modeler are on vacation or call in sick.

If the development team includes resources suited for working with databases, it is good for them to know the software engineer has mastered the essential database concepts. That way, they know there is a containment network to prevent errors from reaching the final product and the user’s hands if they miss an error. Everyone works with less pressure and performs better.

Good team leaders trust their team members to let them do what they do best. So, limit your oversight of the database people to a general review of the finished deliverables to curb any unintentional errors. And by all means, avoid looking over their shoulders to see if they are defining a primary key correctly, writing a SELECT correctly, or employing transaction handling properly to avoid deadlocks. Remember this knowledge is to help the team work better together, not to create frictions!

Original article source at: https://www.vertabelo.com

#database #software #engineer 

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5 Best Important Database Concepts for the Software Engineer
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1656981060

関数をC++からReactNativeにエクスポートする方法

今日も、ネイティブモジュールとC++での経験を共有し続けています。

多くのC/C ++ライブラリがモバイルプラットフォーム用に作成されているので、それらをiOSまたはReactNativeアプリケーションに実装する必要があります。そのため、関数をC++からReactNativeにエクスポートする方法についての記事を書きたいと思います。これは、理解しやすく、初心者の時間を節約できます。新しいreactネイティブアプリケーションから始めます

1.新しいreactネイティブアプリを作成し、ターミナルを開いて実行します

npx react-native init NativeModules

2. Xcodeを開き、NativeModules / ios/NativeModule.xcworkspaceに移動します

3.C++側での作業

新しいC++ファイルを作成し、名前を付けますCpp_to_RN.cpp

新しいC++ファイルを作成すると、XcodeはヘッダーファイルCpp_to_RN.hpp を作成します

まず、「Cpp_to_RN.hppファイルを開き、本体のない関数を含むクラスを作成します。

#ifndef Cpp_to_RN_hpp
#define Cpp_to_RN_hpp#include <stdio.h>
#include <string>class Cpp_to_RN {
public:
    std::string sayHello();
};#endif /* Cpp_to_RN_hpp */

次に、ファイルを開いてCpp_to_RN.cpp、単純な関数「sayHello()」を記述します。

#include "Cpp_to_RN.hpp"
std::string Cpp_to_RN::sayHello(){
    return "Hello from CPP";
}

4.C++ファイルのラッピングに取り組んでいます。

C ++ファイルをラップしてIOS(swift)側にエクスポートするには

a。ObjectiveCファイルを作成して名前を付けますCpp_to_RN.m

名前をに変更Cpp_to_RN.m します Cpp_to_RN.mm

b。ファイルを開き、C++ファイルからWrapCpp_to_RN.mm 関数をラップする本文のコンテンツを記述します。sayHello

#import <Foundation/Foundation.h>
#import "WrapCpp_to_RN.h"
#import "Cpp_to_RN.hpp"@implementation WrapCpp_to_RN- (NSString *) sayHello {
  Cpp_to_RN fromCPP;
    std::string helloWorldMessage = fromCPP.sayHello();
    return [NSString
            stringWithCString:helloWorldMessage.c_str()
            encoding:NSUTF8StringEncoding];
}
@end

c。ヘッダーファイルを作成し、名前を付けますWrapCpp_to_RN.h

wrapSayHello関数をSwiftファイルにエクスポートします

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

5. iOS(Swift)側での作業

C++関数をReactNativeにエクスポートするには

a。Swiftファイルを作成し、名前を付けますSendCpp_to_RN.swift

注:Xcodeは、NativeModules-Bridging-Header.hファイルを作成するように要求します。

クラスSendCpp_to_RNを作成し、次のように宣言しますNSObject

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

requiresMainQueueSetup()アプリケーション実行時の警告を防ぐ関数を作成する

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

WrapCpp_to_RN()fromをラップする関数を記述しますWrapCpp_to_RN.mm

import Foundation@objc(SendCpp_to_RN)
class SendCpp_to_RN : NSObject {
    
  @objc static func requiresMainQueueSetup() -> Bool {
        return false
    }
  
  @objc func fromCpp(_ successCallback: RCTResponseSenderBlock) -> Void {
    successCallback([NSNull(), WrapCpp_to_RN().wrapSayHello() as Any])
    }}

b。Swiftファイルのラップ関数をReactNativeにエクスポートします

を使用してSwiftクラスとその関数をエクスポートするObjectiveCファイルを作成しますCallback

#import <React/RCTBridgeModule.h>
#import <Foundation/Foundation.h>
#import "UIKit/UIKit.h"
@interface RCT_EXTERN_MODULE(SendCpp_to_RN, NSObject)RCT_EXTERN_METHOD(fromCpp:(RCTResponseSenderBlock)successCallback)@end

c。SwiftをReactNativeに接続し、NativeModules-Bridging-Header.h ファイルを開きます

#import <React/RCTBridgeModule.h>#import <React/RCTViewManager.h>#import "WrapCpp_to_RN.h"

6.ReactNative側での作業

Swiftクラスとその関数を呼び出す

import React from 'react';
import {StyleSheet, Text, View, NativeModules, Button} from 'react-native';const App = () => {
  const onPress = () => {
    const {SendCpp_to_RN} = NativeModules;
    SendCpp_to_RN.fromCpp((_err, res) => console.log(res));
  };
  return (
    <View style={styles.container}>
      <Text> Practice !</Text>
      <Button title="C++ to React Native" color="#841584" onPress={onPress} />
    </View>
  );
};
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
});
export default App;

これで完了です。アプリケーションを実行するだけです。

react-native run-ios

または、Xcodeの「実行」ボタンをクリックして、実行内容を確認してください。

私の記事がお役に立てば幸いです。お読みいただきありがとうございます。

 ソース:https ://betterprogramming.pub/native-modules-export-c-function-to-react-native-for-beginners-77e89934b210

#cpp #cplusplus #react 

Cómo Exportar Una Función De C++ A React Native

Hoy sigo compartiendo mi experiencia con el Módulo Nativo y C++.

Dado que veremos muchas bibliotecas C/C++ escribiendo para las plataformas móviles, debemos implementarlas en nuestra aplicación iOS o React Native. Por eso quiero escribir un artículo sobre cómo exportar una función de C++ a React Native, que es fácil de entender y ahorra tiempo a los principiantes. Comenzaré con una nueva aplicación nativa de reacción.

1. Cree una nueva aplicación nativa de reacción, abra su terminal y ejecute

npx react-native init NativeModules

2. Abra Xcode y vaya a NativeModules/ios/NativeModule.xcworkspace

3. Trabajando en el lado de C++

Cree un nuevo archivo C++ y asígnele un nombreCpp_to_RN.cpp

Cuando creamos un nuevo archivo C++, Xcode creará un archivo de encabezado Cpp_to_RN.hpp para nosotros

Primero, abra el archivo " Cpp_to_RN.hpp" y cree una clase que incluya una función sin el cuerpo.

#ifndef Cpp_to_RN_hpp
#define Cpp_to_RN_hpp#include <stdio.h>
#include <string>class Cpp_to_RN {
public:
    std::string sayHello();
};#endif /* Cpp_to_RN_hpp */

Luego abre el Cpp_to_RN.cpparchivo y escribe una función simple “ sayHello()

#include "Cpp_to_RN.hpp"
std::string Cpp_to_RN::sayHello(){
    return "Hello from CPP";
}

4. Trabajando en el archivo Wrapping C++.

Para envolver los archivos C++ y exportarlos al lado IOS (swift)

una. Cree un archivo Objective C y asígnele un nombreCpp_to_RN.m

Renombrar el Cpp_to_RN.m a Cpp_to_RN.mm

b. Abra el WrapCpp_to_RN.mm archivo y escriba el contenido del cuerpo que envolverá la función sayHellodel archivo C++.

#import <Foundation/Foundation.h>
#import "WrapCpp_to_RN.h"
#import "Cpp_to_RN.hpp"@implementation WrapCpp_to_RN- (NSString *) sayHello {
  Cpp_to_RN fromCPP;
    std::string helloWorldMessage = fromCPP.sayHello();
    return [NSString
            stringWithCString:helloWorldMessage.c_str()
            encoding:NSUTF8StringEncoding];
}
@end

C. Cree un archivo de encabezado y asígnele un nombreWrapCpp_to_RN.h

Exportar la wrapSayHellofunción al archivo Swift

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

5. Trabajando en el lado de iOS (Swift)

Para exportar la función C++ a React Native

una. Cree un archivo Swift y asígnele un nombreSendCpp_to_RN.swift

Nota: Xcode nos pedirá que creemos un NativeModules-Bridging-Header.harchivo para nosotros.

Crear una clase SendCpp_to_RNy declararla comoNSObject

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Escribir una función requiresMainQueueSetup()para evitar advertencias cuando ejecutamos la aplicación.

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Escriba una función para envolver el WrapCpp_to_RN()fromWrapCpp_to_RN.mm

import Foundation@objc(SendCpp_to_RN)
class SendCpp_to_RN : NSObject {
    
  @objc static func requiresMainQueueSetup() -> Bool {
        return false
    }
  
  @objc func fromCpp(_ successCallback: RCTResponseSenderBlock) -> Void {
    successCallback([NSNull(), WrapCpp_to_RN().wrapSayHello() as Any])
    }}

b. Exporte una función de ajuste en un archivo Swift a React Native

Cree un archivo Objective C para exportar la clase Swift y su función usandoCallback

#import <React/RCTBridgeModule.h>
#import <Foundation/Foundation.h>
#import "UIKit/UIKit.h"
@interface RCT_EXTERN_MODULE(SendCpp_to_RN, NSObject)RCT_EXTERN_METHOD(fromCpp:(RCTResponseSenderBlock)successCallback)@end

C. Conecte Swift a React Native, abra el NativeModules-Bridging-Header.h archivo

#import <React/RCTBridgeModule.h>#import <React/RCTViewManager.h>#import "WrapCpp_to_RN.h"

6. Trabajando en el lado de React Native

Llame a la clase Swift y sus funciones

import React from 'react';
import {StyleSheet, Text, View, NativeModules, Button} from 'react-native';const App = () => {
  const onPress = () => {
    const {SendCpp_to_RN} = NativeModules;
    SendCpp_to_RN.fromCpp((_err, res) => console.log(res));
  };
  return (
    <View style={styles.container}>
      <Text> Practice !</Text>
      <Button title="C++ to React Native" color="#841584" onPress={onPress} />
    </View>
  );
};
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
});
export default App;

Y listo, solo ejecuta la aplicación

react-native run-ios

O simplemente haga clic en el botón "ejecutar" en Xcode y vea lo que hemos hecho.

Espero que mi artículo te sea útil, gracias por tu tiempo de lectura.

 Fuente: https://betterprogramming.pub/native-modules-export-c-function-to-react-native-for-beginners-77e89934b210

#cpp #cplusplus #react 

黎 飞

黎 飞

1656984600

如何将函数从 C++ 导出到 React Native

今天,我继续分享我在 Native Module 和 C++ 方面的经验。

由于我们将看到很多为移动平台编写的 C/C++ 库,因此我们需要将它们实现到我们的 iOS 或 React Native 应用程序中。这就是为什么我想写一篇关于如何将一个函数从 C++ 导出到 React Native 的文章,它易于理解并且为初学者节省了时间。我将从一个新的 react native 应用程序开始

1.新建一个react native app,打开你的终端运行

npx react-native init NativeModules

2. 打开 Xcode 并导航到 NativeModules/ios/NativeModule.xcworkspace

3. 在 C++ 端工作

创建一个新的 C++ 文件并命名Cpp_to_RN.cpp

当我们创建一个新的 C++ 文件时,Xcode 会Cpp_to_RN.hpp 为我们创建一个头文件

首先,打开“ Cpp_to_RN.hpp文件,并创建一个包含没有主体的函数的类。

#ifndef Cpp_to_RN_hpp
#define Cpp_to_RN_hpp#include <stdio.h>
#include <string>class Cpp_to_RN {
public:
    std::string sayHello();
};#endif /* Cpp_to_RN_hpp */

然后打开Cpp_to_RN.cpp文件,写一个简单的函数“ sayHello()

#include "Cpp_to_RN.hpp"
std::string Cpp_to_RN::sayHello(){
    return "Hello from CPP";
}

4. 处理包装 C++ 文件。

包装 C++ 文件并将它们导出到 IOS (swift) 端

一个。创建一个Objective C文件并命名Cpp_to_RN.m

重命名Cpp_to_RN.m Cpp_to_RN.mm

湾。打开WrapCpp_to_RN.mm 文件并编写将包装sayHelloC++ 文件中的函数的正文内容。

#import <Foundation/Foundation.h>
#import "WrapCpp_to_RN.h"
#import "Cpp_to_RN.hpp"@implementation WrapCpp_to_RN- (NSString *) sayHello {
  Cpp_to_RN fromCPP;
    std::string helloWorldMessage = fromCPP.sayHello();
    return [NSString
            stringWithCString:helloWorldMessage.c_str()
            encoding:NSUTF8StringEncoding];
}
@end

C。创建头文件并命名WrapCpp_to_RN.h

将函数导出wrapSayHello到 Swift 文件

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

5. 在 iOS (Swift) 端工作

将 C++ 函数导出到 React Native

一个。创建一个 Swift 文件并命名SendCpp_to_RN.swift

注意:Xcode 会要求我们为我们创建一个NativeModules-Bridging-Header.h文件。

创建一个类SendCpp_to_RN并将其声明为NSObject

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

编写一个函数requiresMainQueueSetup()来防止我们运行应用程序时出现警告

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

编写一个函数来包装WrapCpp_to_RN()fromWrapCpp_to_RN.mm

import Foundation@objc(SendCpp_to_RN)
class SendCpp_to_RN : NSObject {
    
  @objc static func requiresMainQueueSetup() -> Bool {
        return false
    }
  
  @objc func fromCpp(_ successCallback: RCTResponseSenderBlock) -> Void {
    successCallback([NSNull(), WrapCpp_to_RN().wrapSayHello() as Any])
    }}

湾。将 Swift 文件中的包装函数导出到 React Native

创建一个 Objective C 文件以导出 Swift 类及其函数,使用Callback

#import <React/RCTBridgeModule.h>
#import <Foundation/Foundation.h>
#import "UIKit/UIKit.h"
@interface RCT_EXTERN_MODULE(SendCpp_to_RN, NSObject)RCT_EXTERN_METHOD(fromCpp:(RCTResponseSenderBlock)successCallback)@end

C。将 Swift 连接到 React Native,打开NativeModules-Bridging-Header.h 文件

#import <React/RCTBridgeModule.h>#import <React/RCTViewManager.h>#import "WrapCpp_to_RN.h"

6. 在 React Native 方面工作

调用 Swift 类及其函数

import React from 'react';
import {StyleSheet, Text, View, NativeModules, Button} from 'react-native';const App = () => {
  const onPress = () => {
    const {SendCpp_to_RN} = NativeModules;
    SendCpp_to_RN.fromCpp((_err, res) => console.log(res));
  };
  return (
    <View style={styles.container}>
      <Text> Practice !</Text>
      <Button title="C++ to React Native" color="#841584" onPress={onPress} />
    </View>
  );
};
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
});
export default App;

我们完成了,只需运行应用程序

react-native run-ios

或者只需单击 Xcode 上的“运行”按钮,看看我们做了什么。

希望我的文章对您有所帮助,感谢您的阅读时间。

 来源:https ://betterprogramming.pub/native-modules-export-c-function-to-react-native-for-beginners-77e89934b210

#cpp #cplusplus #react 

Como Exportar Uma Função De C++ Para React Native

Hoje, continuo compartilhando minha experiência com o Módulo Nativo e C++.

Como veremos muitas bibliotecas C/C++ escrevendo para plataformas móveis, precisamos implementá-las em nosso aplicativo iOS ou React Native. É por isso que quero escrever um artigo sobre como exportar uma função de C++ para React Native, que é fácil de entender e economiza tempo para iniciantes. Vou começar com um novo aplicativo nativo de reação

1. Crie um novo aplicativo nativo de reação, abra seu terminal e execute

npx react-native init NativeModules

2. Abra o Xcode e navegue até NativeModules/ios/NativeModule.xcworkspace

3. Trabalhando no lado C++

Crie um novo arquivo C++ e nomeie-oCpp_to_RN.cpp

Quando criamos um novo arquivo C++, o Xcode criará um arquivo de cabeçalho Cpp_to_RN.hpp para nós

Primeiro, abra o arquivo “ Cpp_to_RN.hpp e crie uma classe que inclua uma função sem o corpo.

#ifndef Cpp_to_RN_hpp
#define Cpp_to_RN_hpp#include <stdio.h>
#include <string>class Cpp_to_RN {
public:
    std::string sayHello();
};#endif /* Cpp_to_RN_hpp */

Em seguida, abra o Cpp_to_RN.cpparquivo e escreva uma função simples “ sayHello()

#include "Cpp_to_RN.hpp"
std::string Cpp_to_RN::sayHello(){
    return "Hello from CPP";
}

4. Trabalhando no arquivo C++ de encapsulamento.

Para encapsular os arquivos C++ e exportá-los para o lado IOS (swift)

uma. Crie um arquivo Objective C e nomeie-oCpp_to_RN.m

Renomeie o Cpp_to_RN.m para Cpp_to_RN.mm

b. Abra o WrapCpp_to_RN.mm arquivo e escreva o conteúdo do corpo que envolverá a função sayHellodo arquivo C++.

#import <Foundation/Foundation.h>
#import "WrapCpp_to_RN.h"
#import "Cpp_to_RN.hpp"@implementation WrapCpp_to_RN- (NSString *) sayHello {
  Cpp_to_RN fromCPP;
    std::string helloWorldMessage = fromCPP.sayHello();
    return [NSString
            stringWithCString:helloWorldMessage.c_str()
            encoding:NSUTF8StringEncoding];
}
@end

c. Crie um arquivo de cabeçalho e nomeie-oWrapCpp_to_RN.h

Exporte a wrapSayHellofunção para o arquivo Swift

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

5. Trabalhando no lado iOS (Swift)

Para exportar a função C++ para React Native

uma. Crie um arquivo Swift e nomeie-oSendCpp_to_RN.swift

Observação: o Xcode nos pedirá para criar um NativeModules-Bridging-Header.harquivo para nós.

Crie uma classe SendCpp_to_RNe declare-a comoNSObject

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Escreva uma função requiresMainQueueSetup()para evitar avisos quando executamos o aplicativo

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Escreva uma função para envolver o WrapCpp_to_RN()fromWrapCpp_to_RN.mm

import Foundation@objc(SendCpp_to_RN)
class SendCpp_to_RN : NSObject {
    
  @objc static func requiresMainQueueSetup() -> Bool {
        return false
    }
  
  @objc func fromCpp(_ successCallback: RCTResponseSenderBlock) -> Void {
    successCallback([NSNull(), WrapCpp_to_RN().wrapSayHello() as Any])
    }}

b. Exporte uma função wrap no arquivo Swift para React Native

Crie um arquivo Objective C para exportar a classe Swift e sua função usandoCallback

#import <React/RCTBridgeModule.h>
#import <Foundation/Foundation.h>
#import "UIKit/UIKit.h"
@interface RCT_EXTERN_MODULE(SendCpp_to_RN, NSObject)RCT_EXTERN_METHOD(fromCpp:(RCTResponseSenderBlock)successCallback)@end

c. Conecte o Swift ao React Native, abra o NativeModules-Bridging-Header.h arquivo

#import <React/RCTBridgeModule.h>#import <React/RCTViewManager.h>#import "WrapCpp_to_RN.h"

6. Trabalhando no lado React Native

Chame a classe Swift e suas funções

import React from 'react';
import {StyleSheet, Text, View, NativeModules, Button} from 'react-native';const App = () => {
  const onPress = () => {
    const {SendCpp_to_RN} = NativeModules;
    SendCpp_to_RN.fromCpp((_err, res) => console.log(res));
  };
  return (
    <View style={styles.container}>
      <Text> Practice !</Text>
      <Button title="C++ to React Native" color="#841584" onPress={onPress} />
    </View>
  );
};
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
});
export default App;

E pronto, basta executar o aplicativo

react-native run-ios

Ou apenas clique no botão “executar” no Xcode e veja o que fizemos.

Espero que meu artigo seja útil para você, obrigado pelo tempo de leitura.

 Fonte: https://betterprogramming.pub/native-modules-export-c-function-to-react-native-for-beginners-77e89934b210

#cpp #cplusplus #react 

Hoang  Ha

Hoang Ha

1656981000

Cách Xuất Một Hàm Từ C ++ Sang React Native

Hôm nay, tôi tiếp tục chia sẻ kinh nghiệm của mình với Native Module và C ++.

Vì chúng ta sẽ thấy rất nhiều thư viện C / C ++ viết cho nền tảng di động, chúng ta cần triển khai chúng cho ứng dụng iOS hoặc React Native của mình. Đó là lý do mình muốn viết một bài hướng dẫn cách export một hàm từ C ++ sang React Native dễ hiểu và tiết kiệm thời gian cho người mới bắt đầu. Tôi sẽ bắt đầu với một ứng dụng gốc phản ứng mới

1. Tạo một ứng dụng gốc phản ứng mới, mở thiết bị đầu cuối của bạn và chạy

npx react-native init NativeModules

2. Mở Xcode và điều hướng đến NativeModules / ios / NativeModule.xcworkspace

3. Làm việc trên C ++

Tạo một tệp C ++ mới và đặt tên cho nóCpp_to_RN.cpp

Khi chúng tôi tạo tệp C ++ mới, Xcode sẽ tạo tệp tiêu đề Cpp_to_RN.hpp cho chúng tôi

Đầu tiên, mở tệp Cpp_to_RN.hpp“” và tạo một lớp bao gồm một hàm không có phần thân.

#ifndef Cpp_to_RN_hpp
#define Cpp_to_RN_hpp#include <stdio.h>
#include <string>class Cpp_to_RN {
public:
    std::string sayHello();
};#endif /* Cpp_to_RN_hpp */

Sau đó, mở Cpp_to_RN.cpptệp và viết một hàm đơn giản “ sayHello()

#include "Cpp_to_RN.hpp"
std::string Cpp_to_RN::sayHello(){
    return "Hello from CPP";
}

4. Thao tác trên Wrapping C ++ file.

Để bọc các tệp C ++ và xuất chúng sang phía IOS (nhanh chóng)

một. Tạo một tệp Objective C và đặt tên cho nóCpp_to_RN.m

Đổi tên Cpp_to_RN.m thành Cpp_to_RN.mm

b. Mở WrapCpp_to_RN.mm tệp và viết nội dung phần nội dung sẽ bọc hàm sayHellotừ tệp C ++.

#import <Foundation/Foundation.h>
#import "WrapCpp_to_RN.h"
#import "Cpp_to_RN.hpp"@implementation WrapCpp_to_RN- (NSString *) sayHello {
  Cpp_to_RN fromCPP;
    std::string helloWorldMessage = fromCPP.sayHello();
    return [NSString
            stringWithCString:helloWorldMessage.c_str()
            encoding:NSUTF8StringEncoding];
}
@end

c. Tạo một tệp tiêu đề và đặt tên cho nóWrapCpp_to_RN.h

Xuất wrapSayHellohàm sang tệp Swift

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

5. Làm việc trên iOS (Swift)

Để xuất hàm C ++ sang React Native

một. Tạo một tệp Swift và đặt tên cho nóSendCpp_to_RN.swift

Lưu ý: Xcode sẽ yêu cầu chúng tôi tạo một NativeModules-Bridging-Header.htệp cho chúng tôi.

Tạo một lớp SendCpp_to_RNvà khai báo nó làNSObject

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Viết một hàm requiresMainQueueSetup()để ngăn cảnh báo khi chúng tôi chạy ứng dụng

#import <Foundation/Foundation.h>
@interface WrapCpp_to_RN : NSObject
- (NSString *) wrapSayHello;
@end

Viết một hàm để bọc WrapCpp_to_RN()từWrapCpp_to_RN.mm

import Foundation@objc(SendCpp_to_RN)
class SendCpp_to_RN : NSObject {
    
  @objc static func requiresMainQueueSetup() -> Bool {
        return false
    }
  
  @objc func fromCpp(_ successCallback: RCTResponseSenderBlock) -> Void {
    successCallback([NSNull(), WrapCpp_to_RN().wrapSayHello() as Any])
    }}

b. Xuất một hàm bọc trong tệp Swift sang React Native

Tạo một tệp Objective C để xuất lớp Swift và chức năng của nó bằng cách sử dụngCallback

#import <React/RCTBridgeModule.h>
#import <Foundation/Foundation.h>
#import "UIKit/UIKit.h"
@interface RCT_EXTERN_MODULE(SendCpp_to_RN, NSObject)RCT_EXTERN_METHOD(fromCpp:(RCTResponseSenderBlock)successCallback)@end

c. Kết nối Swift với React Native, mở NativeModules-Bridging-Header.h tệp

#import <React/RCTBridgeModule.h>#import <React/RCTViewManager.h>#import "WrapCpp_to_RN.h"

6. Làm việc ở phía React Native

Gọi lớp Swift và các chức năng của nó

import React from 'react';
import {StyleSheet, Text, View, NativeModules, Button} from 'react-native';const App = () => {
  const onPress = () => {
    const {SendCpp_to_RN} = NativeModules;
    SendCpp_to_RN.fromCpp((_err, res) => console.log(res));
  };
  return (
    <View style={styles.container}>
      <Text> Practice !</Text>
      <Button title="C++ to React Native" color="#841584" onPress={onPress} />
    </View>
  );
};
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
});
export default App;

Và chúng tôi đã hoàn tất, chỉ cần chạy ứng dụng

react-native run-ios

Hoặc chỉ cần nhấp vào nút “chạy” trên Xcode và xem những gì chúng tôi đã làm.

Tôi hy vọng bài viết của tôi hữu ích cho bạn, cảm ơn bạn đã dành thời gian đọc.

 Nguồn: https://betterprogramming.pub/native-modules-export-c- Chức năng-to-react-native-for-beginners-77e89934b210

#cpp #cplusplus #react