C++11 introduced serveral contructor-related enhancements including:
- Class member initializers
- Delegating controctors
This article discusses about Class member initializers only.
Class member initializers are also called in-class initializers. C++11 follows other programming language that let you initializer a class member directly during its declaration:
Class M { // C++11 int j = 5; // in-class initializer bool flag(false); // another in-class initializer public: M(); }; M m1; // m1.j = 5, m1.flag = false
The complier transforms every member initializers(such as int j = 5) into a controctor‘s member initializer. Therefore, the declaration of class M above is semantically equalment to the following C++03 class definition:
class M2{ int j; bool flag; public: M2(): j(5), flag(false) {} }
If the constructor includes an explict member initializer for a member that also has an in-class initializer, the controctor‘s member intializer will override the in-class initializer.
class M2{ int j = 7; // in-class initializer public: M2(); // j = 7 M2(int i): j(i) {} // overrides j‘s in-class intializer }; M2 m2; // j = 7 M2 m3(5); // j = 5
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时间: 2024-08-25 16:55:54