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

by

+ is for a class method and - is for an instance method.

E.g.

// Not actually Apple's code.
@interface NSArray : NSObject {
}
+ (NSArray *)array;
- (id)objectAtIndex:(NSUInteger)index;
@end

// somewhere else:

id myArray = [NSArray array];         // see how the message is sent to NSArray?
id obj = [myArray objectAtIndex:4];   // here the message is sent to myArray

// Btw, in production code one uses "NSArray *myArray" instead of only "id".

There’s another question dealing with the difference between class and instance methods.

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