C++ Qt: can't find methods of dynamic library -

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i'm working on application in qt has plug-able. i've looked around while , came upon example plugins in qt: http://doc.qt.digia.com/4.6/tools-echoplugin.html

i've changed little classes. i've added random number generator:

randomgenerator.h:

#ifndef randomnumber_h #define randomnumber_h  class randomnumber { public:     ~randomnumber();     randomnumber();     int getnumber(); };  #endif // randomnumber_h

randomgenerator.cpp:

#include "randomnumber.h" #include <stdio.h> #include <stdlib.h> #include <time.h>  randomnumber::randomnumber() {     srand(time(null)); }  int randomnumber::getnumber(){     return rand() % 20; }

then made small adjustment in plugin:

echoplugin.cpp:

#include <qtgui> #include "randomnumber.h" #include "echoplugin.h"  qstring echoplugin::echo(const qstring &message) {     randomnumber* rn = new randomnumber();     qstring a;     a.setnum(rn->getnumber());     return a; }  q_export_plugin2(echoplugin, echoplugin);

it's simplified version of program i'm working on. other classes , methods of example on given link haven't been altered. when try execute program, same error have own program:

/home/user/qt/v1/echoplugin/echoplugin: symbol lookup error: /home/user/qt/v1/echoplugin/plugins/libechoplugin.so: undefined symbol: _zn12randomnumberc1ev

i ran through c++filt, , said problem lies with

randomnumber::randomnumber()

but can't find error concerning method.

thanks in advance!

edit: time, i've solved problem myself , give explanation programmers encounter same problem.

it's simple solution: if want use code of headers , sourcefiles not in headerfile of interface, have include relative path in .pro-file, , includes both source-files , headerfiles. if wanted use randomnumber class, i'd have add .pro-file of plugin:

headers += ../randomnumber.h sources += ../randomnumber.cpp


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