C + + Initialize_list

Seeing such a thing, you can implement the curly braces ("{" "}") to initialize the container class.

Need to include header files when using

#include <initialize_list>

We've all seen this code.

vector<int1,2,3,4,5  }; or vector<int  1,2,3,4,5 };

The curly brace on the right returns the type of Initialize_list

We can use this in our own class.

class Foo {public:    std::vector<int> data;     // put the initialize_list in the constructor.     foo () {}    foo (std::initializer_list<int> list):d ata (list) {}     void  print () {        for  (auto item:data) {            << Item ;        }         << Endl;    }};

Test it.

int Main () {    1,2,3,4,5  };     1,2,3,4,5  };    Test1.print ();    Test2.print ();     return 0 ;}

Can output normally

The test code for Cppreference is as follows: There's a lot of tricks to see this thing.

1#include <iostream>2#include <vector>3#include <initializer_list>4 5Template <classT>6 structS {7Std::vector<t>v;8S (std::initializer_list<t>l): V (l) {9Std::cout <<"constructed with a"<< l.size () <<"-element list\n";Ten     } One     voidAppend (std::initializer_list<t>l) { A V.insert (V.end (), L.begin (), L.end ()); -     } -std::p air<Constt*, std::size_t> C_arr ()Const { the         return{&v[0], v.size ()};//copy list-initialization in return statement -                                     //This isn't a use of std::initializer_list -     } - }; +  -Template <typename t> + voidTemplated_fn (T) {} A  at intMain () - { -s<int> s = {1,2,3,4,5};//Copy list-initialization -S.append ({6,7,8});//list-initialization in function call -  -Std::cout <<"The vector size is now"<< S.c_arr (). Second <<"ints:\n"; in  -      for(auto n:s.v) toStd::cout << N <<' '; +Std::cout <<'\ n'; -  theStd::cout <<"range-for over brace-init-list: \ n"; *  $      for(intX: {-1, -2, -3})//The rule for auto makes this ranged-for workPanax NotoginsengStd::cout << x <<' '; -Std::cout <<'\ n'; the  +Auto Al = {Ten, One, A};//Special rule for auto A  theStd::cout <<"The list bound to auto have size () ="<< al.size () <<'\ n'; +  -     //Templated_fn ({1, 2, 3});//compiler error! "{1, 2, 3}" is not a expression, $     //It has no type, and so T cannot is deduced $templated_fn<std::initializer_list<int>> ({1,2,3});//OK -templated_fn<std::vector<int>> ({1,2,3});//also OK -}

C + + Initialize_list