Learn How To Use C++ Defaulted Functions For Windows Development With C++ Builder
A defaulted function is a function that contains =default; in its prototype. This construction indicates that the function’s default definition should be used. Defaulted functions are a C++11 specific feature.
Defaulted functions example
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class A { A() = default; // OK A& operator = (A & a) = default; // OK void f() = default; // ill-formed, only special member function may be defaulted }; |
By default, C++ provides four default special member functions. Users may override these defaults.
- destructor
- default constructor
- copy constructor
- copy assignment
operator =
Also by default, C++ applies several global operators to classes. Users may provide class-specific operators.
- sequence
operator , - address-of
operator & - indirection
operator * - member access
operator -> - member indirection
operator ->* - free-store allocation
operator new - free-store deallocation
operator delete
The management of defaults has several problems:
- Constructor definitions are coupled; declaring any constructor suppresses the default constructor.
- The destructor default is inappropriate to polymorphic classes, requiring an explicit definition.
- Once a default is suppressed, there is no means to resurrect it.
- Default implementations are often more efficient than manually specified implementations.
- Non-default implementations are non-trivial, which affects type semantics, e.g. makes a type non-POD.
- There is no means to prohibit a special member function or global operator without declaring a (non-trivial) substitute.
The most common encounter with these problems is when disabling copying of a class. The accepted technique is to declare a private copy constructor and a private copy assignment operator, and then fail to define either.
Head over and check out more information about defaulted functions on Windows in C++.
