c++ - Add addresses of Objects to a vector in loop -

i need create several objects , put them in list (for using std::vector). also, need list items point addresses of objects changes make objects reflected in list too. thing is, every item in list pointing last object created in loop.

    for(int i=0;i<50;i++){         for(int j=0;j<50;j++){             grass g1;             g1.position.x = i;             g1.position.y = j;             grasslist.push_back(&g1);         }     } 

the attributes of grass objects in list should be..

[0,0] [0,1] [0,2] . . . . [49,49] 

but it's coming out be..

[49,49] [49,49] [49,49] [49,49] . . . [49,49] 

you're pushing pointers local variables vector. local variables destroyed @ end of scope (the second-to-last } in case). therefore, dereferencing of pointers after } undefined behavior. output you're seeing valid result of undefined behavior.

using pointers here doesn't make sense. use them (including new) when absolutely necessary. more info, see why should use pointer rather object itself?

this right way:

std::vector<grass> grasslist;          // ^^^^^ not pointers!  for(int i=0; i<50; ++i) {     for(int j=0; j<50; ++j) {         grass g1;         g1.position.x = i;         g1.position.y = j;         grasslist.push_back(g1);     } }