Qt knowledge points combing - NameSpace namespace

Article directory
namespace role

standard namespace

use namespace

Qt custom namespace

Project source code

development environment

namespace role
Namespace is a scope introduced by ANSIC++ that can be named by users to deal with common name conflicts in programs;

Such as solving the problem: [Exception] Indirect addressing levels are different

In C++, namespaces are declared using namespace, and { } is used to delimit the scope of the namespace, for example:

namespace func{
    int age=18;
}
standard namespace
The standard namespace std in C++, std is the abbreviation of standard, which means "standard namespace"; the functions or objects in the C++ standard library are defined in the namespace std;

Qt has its own namespace: you can see it when you create a new project with a form;

namespace Ui { class MainWindow; }


use namespace
1. Refer to the namespace in the program head, such as:

using namespace std;


2. Add namespaces when referencing variables or methods, such as:

SpaceA::ToolA::Func1();


Qt custom namespace
1. Use namespace and { } to define the scope of the namespace;

2. Write a variable method;

3. Use using namespace xxx to refer to this namespace when referencing;

An example is as follows:

ToolA.h

#ifndef TOOLA_H
#define TOOLA_H
 
#include <QObject>
 
namespace SpaceA {
 
class ToolA : public QObject
{
    Q_OBJECT
public:
    explicit ToolA(QObject *parent = nullptr);
    static void Func1();
    static void Func2();
    static void Func3();
    static void Func4();
 
};//class
 
}//namespace
#endif // TOOLA_H
ToolA.cpp

#include "toola.h"
#include <QDebug>
 
namespace SpaceA {
 
ToolA::ToolA(QObject *parent) : QObject(parent)
{
 
}//class
 
void ToolA::Func1()
{
    qDebug() << "ToolA Func1";
}
 
void ToolA::Func2()
{
    qDebug() << "ToolA Func2";
}
 
void ToolA::Func3()
{
    qDebug() << "ToolA Func3";
}
 
void ToolA::Func4()
{
    qDebug() << "ToolA Func4";
}
 
}//namespace
Referenced in MainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
//using namespace SpaceA; //There is no need to add SpaceA before each call after the namespace is quoted here
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    SpaceA::ToolA::Func1();//After the header refers to the namespace, there is no need to add SpaceA before each call
    SpaceA::ToolA::Func2();
    SpaceA::ToolA::Func3();
    SpaceA::ToolA::Func4();
 
    ToolB::Func1();
    ToolB::Func2();
    ToolB::Func3();
    ToolB::Func4();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
Project source code
Project Git address: lizhifun/QtNamespaceDemo

development environment
Author: Lizhifun

OS: Windows 10 Home Chinese

Compiler: Microsoft Visual C++ Compiler 15.9.28307.1259 (amd64)

Kit: Desktop Qt 5.14.2 MSVC2017 64bit

Qt Creator: 4.11.1
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Copyright statement: This article is an original article by CSDN blogger "One Little Fenghua", which follows the CC 4.0 BY-SA copyright agreement. Please attach the original source link and this statement for reprinting.
Original link: https://blog.csdn.net/tingzhiyi/article/details/112584777