[QCompleter] How to add a qcompleter code to the class CodeEditor?

[irobot]

Hi!
I am programming a text editor and I want to add autocompletion. This source code compiles but when I run it at hit a key, my app stop it execution (it freezes). Can somebody give me a working one?
CodeEditor source code: http://harmattan-dev.nokia.com/docs/library/html/qt4/widgets-codeeditor.html
Working on Win64 seven Qt 4.7.4