class Exception { public: Exception(const wchar_t* szwText) : m_wstrText(szwText) // ВОТ В ЭТОЙ СТРОКЕ {;}; // дальнейшие определения }

    2 answers 2

    Initialization of fields in the constructor. That is, formally, understand it so

     class Exception { public: Exception(const wchar_t* szwText) { m_wstrText = szwText } //дальнейшие определения };

    Only in the first case can the compiler make the code more efficient.

    standard defined in clause 12.6.2

    • <tediousness> only in the first case the copy constructor is called, and in the second, the default constructor and the assignment operator are invoked . </ tediousness> - VladD
    • one
      but can optimize. and call the correct constructor right away. - KoVadim pm
    • @KoVadim: Yeah, has the right, even if different constructors have different side effects - VladD
    • But the funny thing is that the implementation of other designers, who in fact does not use, will require, but the standard requires :) - KoVadim
    • Yeah, so that no one knows what type of optimization worked or not :) - VladD

    To the answer @KoVadim I will add that there are cases when such a construction is not only desirable, but also necessary

    1. Calling the base class constructor
    2. Initiating constant
    3. Initiation of the link (not a pointer!)

    Perhaps something forgot. If anyone specifies other cases, I will be grateful.

    PS Here's another: the included object needs to be initiated by the constructor with parameters, and it has no assignment operator.

    • one
      Initialization of the included object, which has no constructor without parameters, seems to be also impossible without an initialization list. - nnesterov
    • Yes, that's right. - skegg