What's the difference between -(void) and +(void) methods [duplicate]

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Possible Duplicate:

What do the plus and minus signs mean in Objective C next to a method?

Had an error which I fixed by changing -(void) to +(void), but I would like the understand it.

Thanks.

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This denotes an instance method. You must hold a valid instance of the class to call this method.

-(void)

This denotes a class method. You do not need an instance of the class to call this method.

+(void)

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- methods are instance methods and called on a specific instance of a class.

While + methods are class methods and called on the class itself.