Function 指针 static，构造函数

Question

In this code we have static class variable and i need someone to explain what happens here and how i can use it.It is a static class variable and a function that gets the variable with a reference.

class Constructor 
{
private:
static Constructor constructor;
public:
static Constructor* constructor();

};
Constructor Constructor::constructor;
Constructor* constructor::constructor()
{
    return &constructor;
}

Answer 1

一旦您删除错误以便它编译

class Constructor 
{
private:
static Constructor constructor_;
public:
static Constructor* constructor();

};
Constructor Constructor::constructor_;
Constructor* Constructor::constructor()
{
    return &constructor_;
}

您最终会在 static 变量Constructor::constructor_中获得一个私有实例，该实例只能通过其 static 公共Constructor::constructor()方法访问。 这种仅允许创建 class 的单个实例的构造类型称为 singleton。 它是这样使用的：

int main(){   
    auto* s1 = Constructor::constructor();
    auto* s2 = Constructor::constructor();

    std::cout << (s1 == s2);
}

在此处查看工作版本。

有关更多信息，请参阅Singleton 的线程安全初始化。