namespace命名空间是C++中一个非常重要的概念，本文实例展示了namespace的相关语法，供大家参考。具体如下：

本段测试代码包括如下内容：

(1) 如何访问namespace中声明的名称；

(2) namespace导致的相关冲突；

(3) namespace可嵌套；

(4) 可以在namespace中使用using声明和using编译命令；

(5) 未命名的namespace：其作用域为定义该namespace所在的声明区域。C++推荐用来替代static定义静态变量。

具体程序代码如下：

#include <iostream> using namespace std; namespace jerry{ int height; int weight; void showHeight(); string name; } // namespace jerry{ void showHeight() { cout<<"Method 3: Jerry height: "<<height<<" kg"<<endl; } } namespace elements { namespace fire { int flame; using namespace jerry; //(4) can use 'using' in namespace define using std::cout; } float water; } //(5) no name namespace //其作用域为定义时所在的声明域，可用来替换static变量，这是C++标准推荐的行为 namespace { string data; } void testFun(); int main() { cout<<"This code is to test namespace"<<endl; /*not allowed to define namespace in code segment //Error namespace jerry{ int height; int weight; } */ //(1) To access the data in namespace //Method 1: 作用域解析符 jerry::height = 165; cout<<"Method 1: Jerry height: " << jerry::height <<" cm"<<endl; //Method 2: using声明 using jerry::weight; weight = 64; cout<<"Method 2: Jerry weight: " << weight<<" kg"<<endl; //Method 3: using编译指令：All the define data in namespace jerry can be access. using namespace jerry; showHeight(); //(2) about name conflict { jerry::name = "Jerry"; string name = "Tom"; //using jerry::name; Error cout << "name: "<<name<<endl; /* This method will lead conflict with locall parameter using jerry::name; cout << "name: "<<name<<endl; */ cout << "name: "<<jerry::name<<endl; using namespace jerry; //局部变量会覆盖jerry命名空间的name定义 cout << "name: "<<name<<endl; } //(3) namespace can nest elements::fire::flame = 2; using namespace elements::fire; //(5) no name namespace //其作用域为定义时所在的声明域，可用来替换static变量，这是C++标准推荐的行为 data = "hello"; cout<<"No name namespace: data: " << data <<endl; testFun(); } void testFun() { /*not allowed to define namespace in code segment //Error namespace jerry{ int height; int weight; } */ //(5) no name namespace data = "hello in function"; cout<<"No name namespace: data: " << data <<endl; }

运行结果如下图所示：