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I want to access var1, which resides in Class1, from Class2. So I set up accessor methods in Class1 to access and return the var. Then I call this method from Class2 only to get ‘selector not recognized errors’. This issue was dealt with in General/HowToTransmitDataBetweenClasses but the only solution involved using Interface builder and General/IBOutlets ?!?!? surely this is one of the most common things that someone using objC would want to do? is there a better way?


Post code and the exact error message. It’s impossible to say what’s going on otherwise. Are you sure you’re sending the right message from a Class2 instance to a Class1 instance? Is everything capitalized properly?

in Class 2, I have the following function, attached to a button in IB:

-(General/IBAction) getMyVarFromTheOtherCLass:(id)sender{ General/NSString * meNow = General/[ClassOne getMyVariable]; General/NSLog(@”%@”,meNow); }

in Class 1, I have the accessor function:

pushing said button (invoking getMyVarFromTheOtherCLass) gets me: *** +General/[ClassOne getMyVariable]: selector not recognized

That’s because you’re sending a message to a class, while the method is defined on an object (i.e. on an instance of the class).

but class one has stuff running from when it was initially initialized during ‘awakeFromNib’ - I don’t want to create another instance because it will launch all my running threads again. Is there any way for class 2 to see that class 1 already has an instance and address that already running instance?

Yes - General/SingletonDesignPattern, General/SingletonAlternatives

hmmm…this singleton design makes sense in theory but in practice I can’t figure it out.

I put this accessor in class 1:

Now, normally I would instantiate an instance of classOne from classTwo with:

newInstanceOfClassOne = [[classOne alloc] init];

This will give me a NEW instance of classOne - how do I use that singleton accessor to return the ‘already running’ instance and access to its variables?

Your classOne method is a class method, so you’d do [[[ClassOne classOne]. You should never send an alloc/init message to it. The method signature should also be +(General/ClassOne *)classOne.

Link to this discussion from General/HowToTransmitDataBetweenClasses and General/ClassMethodsAndInstanceVariables