如果理解了上节的constructor initializer list的行为,那么不难想到,相比于将正确的值在constructor body里赋给成员变量,不如直接在initializer list里给出。这是因为,constructor initializer list是直接初始化了数据成员(1步),而如果赋值在constructor body里,就是在进入body前进行了初始化,然后在body中进行赋值(2步)...
本文探讨构造函数初始值列表(constructor initializer list)这一C++特性，主要关注其行为、适用场景以及相关细节。构造函数初始值列表用于在构造函数定义时直接初始化数据成员，简化代码并提升效率。构造函数初始值列表的行为遵循三步初始化流程。首先，使用初始值列表中的值进行初始化（通过调用与实参相对应的构造...
Furthermore,if a class doesn't have a default constructor, or you have aconstmember variable, youmustuse an initializer list: classA{public:A(intx){x_=x;}intx_;}classB{public:B():a(3),y(2)// 'a' and 'y' MUST be initialized in an initializer list;{// it is an error not ...
myclass foo {10,20};//calls initializer_list constructormyclass bar (10,20);//calls first constructor 仅可以从braced-init-list推导出initializer_list<T>。这一过程中,编译器自动查询哪些构造函数可以用initializer_list<T>作为参数,并据此确定initializer_list的模板参数T的类型,从而对braced-init-list做类...
In the following example, our Foo(int, int) constructor has been updated to use a member initializer list to initialize m_x, and m_y: #include <iostream> class Foo { private: int m_x {}; int m_y {}; public: Foo(int x, int y) : m_x { x }, m_y { y } // here's ...
class initializer_list { private: const _E* _M_array; size_t _M_len; // The compiler can call a private constructor. constexpr initializer_list(const_iterator __a, size_type __l) : _M_array(__a), _M_len(__l) { } }; ...
With C++ classes one can have the option of initializing the class's data members in the constructor's initializer list. Using constructor initializer lists in C++ Builder is discussed. It is shown that they represent the preferred way of initializing a class.Kent Reisdorph...
Without the constructor for the initializer list, the constructor taking two ints would be called to initialize q and s, while the initialization of r would be invalid. initializer_list source code constexper 关键字:const并未区分出编译期常量和运行期常量, constexpr限定在了编译期常量。
他认为,构造std::initializer_list之前编译器会先构造一个std::array,然后使用std::array的begin()和size()构造std::initializer_list。这种说法有一处错误。编译器不会构造std::array,而是在栈上直接构造一个数组const T[N]。在栈上构造的数组会像其他变量一样,在离开作用域时自动析构,不需要手动管理内存,所以...
structS{intn;S(int);// constructor declarationS():n(7){}// constructor definition:// ": n(7)" is the initializer list// ": n(7) {}" is the function body};S::S(intx):n{x}{}// constructor definition: ": n{x}" is the initializer listintmain(){S s;// calls S::S()S...