c++ - Retrieve object instance from map -


i'm new c++ , i'm trying make little game. have class named "unitcontroller" stores multiple instances of class "unit" in map. class has method "getunit" should return 1 of stored units.

it seems method partially working. think copy of unit instead of requested instance.

could point me int right direction?

#include "unitcontroller.h" #include "unit.h"  using namespace ci; using std::map;  unitcontroller::unitcontroller() { }  void unitcontroller::addunit( vec2f position ) {     unit munit = unit();     munit.setup( position );     units.insert( std::pair<int,unit>( units.size()+1, munit ) ); }  unit unitcontroller::getunit( int k ) {     unit selectedunit = units[0];     return selectedunit; }  void unitcontroller::update() {     for( map<int,unit>::iterator u = units.begin(); u != units.end(); ++u ){         u->second.update();     } }  void unitcontroller::draw() {     for( map<int,unit>::iterator u = units.begin(); u != units.end(); ++u ){         u->second.draw();     } }

the method:

unit unitcontroller::getunit( int k ) {     unit selectedunit = units[0];     return selectedunit; }

is returning a, possibly default, copy of element index 0 (do mean ignore k?). if wish avoid copy being returned return reference instead element @ index 0, not local variable selectedunit:

unit& unitcontroller::getunit( int k ) {     return units[k]; }

if entry keyed k removed map caller has reference unit of entry has dangling reference, use of undefined behaviour. there few things consider try , avoid this:

  1. does client of unitcontroller require direct access unit in map? if not , client requires update attributes of unit modify unitcontroller interface support updates unit without providing client direct access.
  2. if client require direct access consider using std::shared_ptr<unit> instead of unit entry value type (and don't return reference in case). address dangling reference problem mean caller have access unit no longer in unitcontroller?

operator[] create entry in map key not exist:

inserts new element container using key key , default constructed mapped value , returns reference newly constructed mapped value. if element key key exists, no insertion performed , reference mapped value returned.

if wish not have behaviour use find() , decide on action take if entry key k not exist.


Comments

Post a Comment

Popular posts from this blog

php - mySql Join with 4 tables -

select * web_user e inner join web_audio ce on ce.uid = e.uid inner join web_videos c on c.uid = e.uid inner join web_images d on d.uid = e.uid e.uid = '1' we have scenario have 4 tables , want fetch records on basis of uid web_user table rest of tables fetch records on basis of web_user uid. have 6 records database. returning 8 time. below response of mysql query. uid ufname ulname uemail username upassword uaddress ucity ustate uzipcode uphone uimage usertype ugenre website biography uverifycode featured activate ustatus upaid aid uid a_filename a_uploadname a_genre a_singername a_approve a_price vid uid v_filename v_uploadname v_short_desc v_singername v_approve v_price iid uid upload_file i_approve ========================== 1 muhammad mohsin mohsin@balianti.com mohsin 213123 test addresss 0 1 40100 333-2335-5555 fds_896_autumn-mist.jpg 1 6 null null 202cb962ac59075b964b07152d234b70 1 1 1 1 1 1 asd muhammad_709.mp3 5 asd 0 0.00 1 1 test video muhammad_578.flv ...
Read more

css - Text drops down with smaller window -

i've adapted css use in website , can't quite figure out why 1 aspect of page acting way acting. basically, when shrink window below size horizontally, of text "drops down". becomes issue if user viewing website through ipad vertical orientation. can view issue here . i'm hoping make if window gets smaller, placement of text remains intact. the problem area not have enough space put both side navigation , content on 1 line. make automatically adjust page's width when exceeds decrements of width. this code example, , highly unlikely work. if see css more clearly, provide exact code. @media , (max-width:960px) { /* assuming #wrapper 960px across */ #content {width:560px;} /* opposed 720px */ } edit the content drops down @ 980px, have shrink width after there. @media , (max-width:980px) { #container {width:520px;} }
Read more

c# - DetailsView in ASP.Net - How to add another column on the side/add a control in each row? -

i have detailsview control on page used edit various fields of record, works in respect. i looking way add 1 column (and if works, why not more) right, absolutely read-only, show same fields of record comparison purposes. i aware there no obvious way such thing out of box detailsview . have looked other controls (transposed gridview , recommended formview , listview ), nothing satisfies. have special data binding setup using detailsview , can't out of without losing features. anyone on how "hack in" additional columns (for display only) on detailsview ? the solution have now, use second detailsview , visible set false in aspx. in code, make sure databind hidden detailsview hosts data third column first, initial detailsview named itemdetails . and in item created event, pass third column html rendering of hidden controls (in last code block) : protected void itemdetails_itemcreated(object sender, eventargs e) { if (dataite...
Read more