C++11关于function、bind的详解

std::function

转载自：http://en.cppreference.com/w/cpp/utility/functional/function

 

C++

 

Utilities library

 

Function objects

 

std::function

 

Defined in header <functional>

  template< class >
class function; /* undefined */ (since C++11)template< class R, class... Args >
class function<R(Args...)> (since C++11)   

Class template std::function is a general-purpose polymorphic function wrapper. Instances of std::function can store, copy, and invoke any Callable target -- functions, lambda expressions, bind expressions, or other function objects, as well as pointers to member functions and pointers to data members.

The stored callable object is called the target of std::function. If a std::function contains no target, it is calledempty. Invoking the target of an empty std::function results in std::bad_function_call exception being thrown.

std::function satisfies the requirements of CopyConstructible and CopyAssignable.

Member types

TypeDefinitionresult_typeRargument_typeT if sizeof...(Args)==1 and T is the first and only type in Args...first_argument_typeT1 if sizeof...(Args)==2 and T1 is the first of the two types in Args...second_argument_typeT2 if sizeof...(Args)==2 and T2 is the second of the two types in Args...

Member functions

(constructor)

constructs a new std::function instance 
(public member function)

(destructor)

destroys a std::function instance 
(public member function)

operator=

assigns a new target 
(public member function)

swap

swaps the contents 
(public member function)

assign

assigns a new target 
(public member function)

operator bool

checks if a valid target is contained 
(public member function)

operator()

invokes the target 
(public member function)

Target access

target_type

obtains the typeid of the stored target of a std::function 
(public member function)

target

obtains a pointer to the stored target of a std::function 
(public member function)

Non-member functions

std::swap(std::function)

(C++11)

specializes the std::swap algorithm 
(function template)

operator==operator!=

compares an std::function with std::nullptr 
(function template)

Helper classes

std::uses_allocator<std::function>

(C++11)

specializes the std::uses_allocator type trait 
(class template specialization)

Example

Run this code

#include <functional>#include <iostream> struct Foo {    Foo(int num) : num_(num) {}    void print_add(int i) const { std::cout << num_+i << '\n'; }    int num_;}; void print_num(int i){    std::cout << i << '\n';} struct PrintNum {    void operator()(int i) const    {        std::cout << i << '\n';    }}; int main(){    // store a free function    std::function<void(int)> f_display = print_num;    f_display(-9);     // store a lambda    std::function<void()> f_display_42 = []() { print_num(42); };    f_display_42();     // store the result of a call to std::bind    std::function<void()> f_display_31337 = std::bind(print_num, 31337);    f_display_31337();     // store a call to a member function    std::function<void(const Foo&, int)> f_add_display = &Foo::print_add;    const Foo foo(314159);    f_add_display(foo, 1);     // store a call to a member function and object    using std::placeholders::_1;    std::function<void(int)> f_add_display2= std::bind( &Foo::print_add, foo, _1 );    f_add_display2(2);     // store a call to a member function and object ptr    std::function<void(int)> f_add_display3= std::bind( &Foo::print_add, &foo, _1 );    f_add_display3(3);     // store a call to a function object    std::function<void(int)> f_display_obj = PrintNum();    f_display_obj(18);}

Output:

-9423133731416031416131416218