"AudioAppComponent" is "not a class or struct name"? (Resolved)

I have my basic GUI system for a synth starting to come together so I want to start adding sound from some tutorials I’m following.

However, it doesn’t seem to work and I can’t understand why. For example, the basic code from the Sine Synth Tutorial is:

class MainContentComponent   : public AudioAppComponent
        addAndMakeVisible (frequencySlider);
        frequencySlider.setRange (50.0, 5000.0);
        frequencySlider.setSkewFactorFromMidPoint (500.0); // [4]
        frequencySlider.onValueChange = [this]
            if (currentSampleRate > 0.0)

        setSize (600, 100);
        setAudioChannels (0, 2); // no inputs, two outputs

But I can’t even get this to work in my design. My otherwise “working” GUI demo has a MainContentComponent that inherits from Component. But this does not seem to let me do things like setAudioChannels(0, 2);

If I try to make it or a new class that inherits from AudioAppComponent it tells me that doesn’t exist. I don’t get it.

If I started this project by selecting “GUI Application” would that cause problems? What am I supposed to do to fix this so I can get the basic audio functions working?

Also is there a difference in concept between “MainComponent” and “MainContentComponent”? I see some demos use one or the other.


Edit: I presume this has to do with what you select when you start a project and there’s no turning back after that. Started an “Audio Application” instead and copied my GUI code into it to integrate and now I can do all those commands.

The AudioAppComponent is in the module juce_audio_utils, which is not selected by default in some project templates. But you can always add it at later stage in the modules section of Projucer.

Isn’t the problem with the code in the post the setAudioChannels (0, 2); line? Its been put in the body of the class definition rather than in the constructor where it should be, so its basically a syntax error and confusing the compiler.

Well spotted, that’s the next error, which XCode calls:
C++ requires a type specifier for all declarations. That needs fixing as well.