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std::function::operator bool

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< cpp‎ | utility‎ | functional‎ | function
Revision as of 17:12, 22 January 2013 by Nate (Talk | contribs)

 
 
 
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explicit operator bool() const;
(since C++11)

Checks whether *this stores a callable function target, i.e. is not empty.

Contents

Parameters

(none)

Return value

true if *this stores a callable function target, false otherwise.

Exceptions

noexcept specification:  
noexcept
  

Example

#include <functional>
#include <iostream>
 
typedef std::function<void(int)> SomeVoidFunc;
 
class C {
  public:
    C(SomeVoidFunc void_func = nullptr)
        : void_func_(void_func)
    {
        if (!void_func_) {
            void_func_ = std::bind(&C::default_func, this, std::placeholders::_1);
        }
        void_func_(7);
    }
 
    void default_func(int i) { std::cout << i << '\n'; };
 
  private:
    SomeVoidFunc void_func_;
};
 
void user_func(int i)
{
    std::cout << (i + 1) << '\n';
}
 
int main()
{
    C c1;
    C c2(user_func);
}

Output:

7
8