Difference between revisions of "cpp/language/this"
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Inside non-static member function, holds a pointer to the class object from which the function was invoked. | Inside non-static member function, holds a pointer to the class object from which the function was invoked. | ||
Revision as of 13:16, 15 June 2012
Inside non-static member function, holds a pointer to the class object from which the function was invoked.
The type of this pointer is cv T* const where T is the class name and cv refers to the cv specifiers of the function the pointer is used in. For example:
| Function signature | Type of this |
|---|---|
| void T::foo() | T* const this; |
| void T::foo() const | const T* const this; |
| void T::foo() volatile | volatile T* const this; |
| void T::foo() const volatile | const volatile T* const this; |
Example
class T { int x; void foo() { this->x = 5; // this used explicitly x = 6; // same as this->x = 6; } void foo() const { this->x = 7; // Error: *this is constant } void foo ( int x ) { // parameter x shadows the attribute with the same name this->x = x; // unqualified x refers to the parameter, but the attribute is still accessible using the this pointer } T& operator= ( const T& b ) { x = b.x; return *this; // this is often used when a reference to the current object is needed } void bar ( const T& b ) { // two ways to call class operators using this (*this) = b; this->operator= ( b ); } void bar() { // methods can be called even when there's no object // the this pointer can be seen like an additional parameter implicitly passed if ( this == NULL ) return; } }; T* pointer = reinterpret_cast<T*>(123); pointer->bar(); // bar is called with 123 (0x7B) as value for this
