Question

What is the difference of using:

+ (id) myMethod;

// Rather than
- (id) myMethod;

Answer 1

Using a + declares the method as a class method, or a method that can be called directly on the class, where the class is the object. So when you have this:

@implementation Foo
+(NSString*)method1 {
  return @"Foo";
}
-(NSString*)method2 {
  return @"Foo";
}
@end

The methods are called in different ways:

[Foo method1];  //=> @"Foo"
Foo* f=[[Foo alloc] init];
[f method2];    //=> @"Foo"

One other thing to note is that class methods don’t have access to an instance, which means they can’t access any kind of instance variables.