# Weird compiler error with Introjucer on tip code

#1

Hi,

on the tip code, compiling the introjucer i get this error under Visual Studio 2005.

```1>w:\sw\juce\extras\introjucer\source\project\jucer_treeviewtypes.cpp(105) : error C2259: 'ProjectInformationComponent' : cannot instantiate abstract class 1> due to following members: 1> 'void juce::Value::Listener::valueChanged(juce::Value &)' : is abstract 1> w:\sw\juce\modules\juce_data_structures\values\juce_value.h(144) : see declaration of 'juce::Value::Listener::valueChanged'```

but looking at the code the juce value object mentioned doesnt seem relevant to the ProjectInformationComponent.

but weirder still, it builds fine under Visual Studio 2010 !!

i tried the obvious cleans and deleting any temp files, to no avail. could this be a compiler bug or something slipping through.

anyone else seen any differences like this?

#2

Ah, this is an old MS bug where it sometimes gets muddled when there are inner classes with the same name.

So if I have a Button::Listener and a Value::Listener class, it sometimes (but not always…) gets them confused, even if you fully specify the type.

That’s why you’ll find a few typedefs in the code like this:

``` /** This typedef is just for compatibility with old code and VC6 - newer code should use Button::Listener instead. */ typedef Button::Listener ButtonListener; ```

I edited that class recently, and obviously forgot to use the “ButtonListener” instead of “Button::Listener” in its declaration.

#3

aha! thanks for this explanation, i thought i was going mad, the error had nothing to do with the listener in question. indeed it’s getting mixed up with another one.

cool. it means i dont have some weird magic somewhere that’s throwing VC2005 over.