direct initialization

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[编辑] 语法

[编辑] 解释

• T如果是一个类类型，构造函数的T进行检查，并选择最佳匹配的重载决议。然后调用该构造函数初始化对象.

  Original:

  If T is a class type, the constructors of T are examined and the best match is selected by overload resolution. The constructor is then called to initialize the object.

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• 否则，如果T是一种非类类型，标准的转换被使用，如果必要的话，将该值转换为other的cv不合格版本的T.

  Original:

  Otherwise, if T is a non-class type, 标准的转换 are used, if necessary, to convert the value of other to the cv-unqualified version of T.

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[编辑] 注释

[编辑] 为例

#include <string>
#include <iostream>
#include <memory>
 
struct Foo {
    int mem;
    explicit Foo(int n) : mem(n) {}
};
 
int main()
{
    std::string s1("test"); // constructor from const char*
    std::string s2(10, 'a');
 
    std::unique_ptr<int> p(new int(1)); // OK: explicit constructors allowed
//  std::unique_ptr<int> p = new int(1); // error: constructor is explicit
 
    Foo f(2); // f is direct-initialized:
              // constructor parameter n is copy-initialized from the rvalue 2
              // f.mem is direct-initialized from the parameter n
//  Foo f2 = 2; // error: constructor is explicit
 
    std::cout << s1 << ' ' << s2 << ' ' << *p << ' ' << f.mem  << '\n';
}

test aaaaaaaaaa 1 2

[编辑] 另请参阅

• 默认的初始化
• 复制初始化
• 集合初始化
• 表初始化