How to use translation in Qt? - c++

Question

I'm trying to use Qt's tr() function for translation.
In .pro file I have:
TRANSLATIONS += languages/myapp_en.ts \
languages/myapp_es.ts
and in main.cpp:
QTranslator translator;
translator.load("myapp_es"); //espanol
app.installTranslator(&translator);
I run lupdate and the files myapp_en.ts, myapp_es.ts are generated.
I edit the file myapp_es.ts, for example:
<context>
<name>Example</name>
<message>
<location filename="../example.cpp" line="24"/>
<source>Good night</source>
<translation>Buenas noches</translation> <!-- THIS IS MY EDIT -->
</message>
</context>
Then I run lrelease so the files myapp_en.qm, myapp_es.qm are generated.
Then I use tr() in code like this:
button->setText(tr("Good night"));
inside the constructor of a Q_OBJECT class.
But the text is still showing in English ("Good night"), and not in Spanish.
What am I doing wrong?
Edit:
Putting the *.qm files in the correct directory solved the problem. Just had to make sure it's in the Release directory and not the Debug.

Answer 1

You need to include the extension .qm and correct path when calling translator.load:
QTranslator translator;
translator.load("languages/myapp_es.qm"); //espanol
app.installTranslator(&translator);

Answer 2

after installing translator you have to call retranslate of ui generated class if applied or call tr again

Answer 3

From the other answers I can see that you're now getting true for load, so it's finding the translation file. What it could then be is that you're installing the translation after the system has already initialised the UI, so you can do one of two things:
Install the translator before you create your UI, for me it would go:
translator.load(someTranslation)
a.installTranslator(&translator)
MainWindow w;
Install the translator after you create the UI, which if you're providing multiple language support is most likely where you'll want it. Qt provides a retranslateUi() function, which when called will update the user interface. There's a question here which shows this in more depth: How to translate language in Qt on the fly. There's a bit more code required for handling the language change event, but it does allow for dynamic language updates.