c++ - Why is the boolean value within a structure within a vector not being updated? -


this might sound basic question, have trying fix simple bug on hour , can't seem understand what's happening.

i have following structure declaration in header file:

struct studentbody {     string name;      vec2 position;      bool disabled;      studentbody(string name, vec2 position) : name(name), position(position) {} };

this structure being filled vector of type:

std::vector<studentbody> students_real;

like this:

students_real =     {         studentbody("student1",vec2(display_width - 50, lower_margin + 100)),         studentbody("student2",vec2(display_width - 100, lower_margin + 100)),         studentbody("student3",vec2(display_width - 150, lower_margin + 100)),         studentbody("student4",vec2(display_width - 200, lower_margin + 100))     };

by default of students have "disabled" set false.

then have "update" method gets triggered screen refresh rate, , within method have following code:

for (auto = students_real.begin(); != students_real.end(); it++)         {             auto student_to_check = *it;              cclog("student %s disabled -> %i",student_to_check.name.c_str(),student_to_check.disabled);              if (student_to_check.name == "student1" || student_to_check.disabled) {                 continue;             }              bool disablestudent = true;              //... custom condition here checks if "disabledstudent" should become false or stay true...              if (disablestudent)             {                 cclog("disabling %s",student_to_check.name.c_str());                  student_to_check.disabled = true;                  cclog("student %s disabled -> %i",student_to_check.name.c_str(),student_to_check.disabled);             }         }

the problem here "disabled" flag not staying true. when check condition @ first it's false. check second condition , if it's satisfied set true. next time loop started condition false.

this makes me believe "auto student_to_check = *it;" gives me copy of structure handle not structure itself? or going on? why can't modify value of structure within vector?

this:

auto student_to_check = *it;

declares local variable copy of structure in vector. iterator points structure in vector, can use:

auto student_to_check = it;

and:

student_to_check->disabled = true;

or more following access in vector's structure. don't need local variable:

it->disabled = true;

even better use c++11's range-based loop, @sp2danny commented:

for(auto& student_to_check : students_real)

student_to_check reference structure in vector instead of local copy, , rest of code remains is.


Comments

Post a Comment

Popular posts from this blog

c# - Validate object ID from GET to POST -

i have method allows user access comment have made on site. have post method lets them update comment. my normal solution send entire comment model through, let them update it, update on database when post back. involve sending commentid through in hiddenfor , can manipulated. how can verify commentid sent in get method same i'm getting in post , not able alter comment wish? how can verify commentid sent in method same i'm getting in post? basically have validate following things in post - user logged-in user. authenticated users post comments. commentid in post , should valid commentid , should present in database. userid associated logged-in user should same userid associated comment . comment should contain userid column, can check @ time of update. to make sure update happens comment has been sent in get - hold commentid in session , in post action compare commentid value in session .
Read more

node.js - Custom Model Validator SailsJS -

when using custom model validator checks record within model. return within spread doesn't seem end control flow. //post.js model /** * custom validator **/ types: { isuservalid: function(user_id) { var promise = require('bluebird'); promise.all([ user.findone({id: user_id}) ]) .spread(function(user) { console.log(user); if (user === null || user === undefined) { console.log('failed'); return false; }else{ console.log('passed'); return true; } }); } }, my response standard validation failed response. { "error": "e_validation", "status": 400, "summary": "1 attribute invalid", "model": "post", "invalidattributes": { "owner": [ { "rule": "isuservalid", ...
Read more

php - Find a regex to take part of Email -

i have following emails need extract part from: bestellnummer xxx: 1 von xxx, 1er pack ------------- anfang der nachricht ------------- foo bar baz foo bar baz // <<<<< need text here ------------- ende der nachricht ------------- ------------- anfang der nachricht ------------- foo bar baz foo bar baz ------------- ende der nachricht ------------- there 0 unlimited occurences of ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- and i'm able extract first part regex: $re = "/------------- .*? -------------.?(.*?).?------------- .*? -------------/s"; but, i'm quite new on learning regex, i'm pretty sure there must better regex extract part (foo bar baz foo bar baz) of text between ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- as can in different languages, i'm using .? to match between hyphens. i...
Read more