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What do the plus and minus signs mean in Objective C next to a method?
What's the difference between using a plus or minus in Objective-C?
For example, most of the time code starts -(void)somethingSomethingelse, but sometimes it will be +(void)somethingSomethingelse
Thanks!
- functions are instance functions and + functions are class (static) functions.
So let's say you have a class called Person, and the following functions
-(void)doSomething;
+(void)doSomethingElse;
You would invoke these functions with the following:
Person *myPerson = [[Person alloc] init];
[myPerson doSomething];
[Person doSomethingElse];
This is more of a syntax description, assuming you understand the concept of class vs instance.
edit:
just to add: In objective-C, you can actually invoke a class function on an instance, but the effect is no different than invoking it on the class itself (essentially compiles to the same thing).
So you can do
[myPerson doSomethingElse]
Generally, you wouldn't do this as it is confusing and misleading to read. I am pointing it out so you won't be surprised if you come across code like this somewhere.
In short, (+) is a class method and (-) is an instance method
See this answer for a full explanation What is the difference between class and instance methods?
member and public functions respectively.
Such that
id object = [[NSObject alloc] init];
+ (id)alloc;
- (id)init;
Where NSObject is a Class and id is an object
If you have ever used C++, a + is equivalent to static
