How are these ObjC declarations different: ie what is this really doing?

Question

I'm trying to understand what this is doing in each case. Can someone explain what the first case is doing in detail and how it differs from the second? Thanks // :)

//declare in first case
NSManagedObjectModel *mom();

NSManagedObjectModel *mom() {
 static NSManagedObjectModel *mom = nil;
//implementation goes here...
 return mom;
}

vs.

//no declaration in second case
- (NSManagedObjectModel *) mom {
 static NSManagedObjectModel *mom = nil;
//implementation goes here...
 return mom;
}

Answer 1

The first is a standalone function; it's not tied to a class. You'd call it like:

NSManagedObjectModel *retVal = mom();

The second is an instance method definition, and thus is defined in the context of a class. You'd call it like:

NSManagedObjectModel *retVal = [someObject mom];