Qt mysql query prepare doesn't work -

i'm building qt application make queries on mysql database. when query.exec("call selectusersphotos()") response fine if set query string on prepare show on code below database doesn't return values , doesn't throw erros.

if (db.open()) {     cout << "querying getuserphotos user " << user->name << endl;      qsqlquery query;      query.prepare("call selectusersphotos()");     query.exec();      while (query.next()) {         userphoto *userphoto = new userphoto();         userphoto->userphotoid = query.value(0).toint();         userphoto->userid      = query.value(1).toint();         userphoto->created     = query.value(2).todatetime();         userphoto->name        = query.value(3).tostring().tostdstring();         usersphotos->push_back(userphoto);     }      query.finish();      db.close();      cout << "photos " << usersphotos->size() << endl; } 

resources: http://qt.developpez.com/doc/4.6/qsqlquery/

"prepares sql query query execution. returns true if query prepared successfully; otherwise returns false."

maybe should try

bool b = query.prepare("call selectusersphotos()");  while(!b)     b = query.prepare("call selectusersphotos()"); query.exec(); 

edit: function signature

bool qsqlquery::prepare ( const qstring & query ) 

so needs address of value u passing rvalue parameter. maybe u should try

qstring qstr("call selectusersphotos()"); query.prepare(qstr); query.exec(qstr); 

note don't know why exec(const qstring & query) works if has same reference parameter.