c++ - How to allow range-for loop on my class? -

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• how make custom type work “range-based loops”? 5 answers

i have class this:

class foo { private:     int a,b,c,d;     char bar;     double m,n public:     //constructors here }; 

i wanna allow range-for loop on class, e.g.

foo foo {/*...*/}; for(auto& f : foo) {   //f specific order such c,b,d,(int)m,(int)bar,a,(int)n } 

how can achieve this? looking @ iterator don't know requirements range-for loop. (please don't ask me use array or stl type)

the loop defined equivalent to:

for ( auto __begin = <begin-expr>,            __end = <end-expr>;       __begin != __end;       ++__begin ) {     auto& f = *__begin;     // loop body } 

where <begin-expr> foo.begin(), or begin(foo) if there isn't suitable member function, , likewise <end-expr>. (this simplification of specification in c++11 6.5.4, particular case range lvalue of class type).

so need define iterator type supports pre-increment ++it, dereference *it , comparison i1 != i2; , either

• give foo public member functions begin() , end(); or
• define non-member functions begin(foo) , end(foo), in same namespace foo can found argument-dependent lookup.