Question

I have been using different methods that are used in Objective-C. Can any one give a good explanation of the difference between following methods?

void append(NSString *msg);
-(void) append:(NSString *)msg;
+(void)append:(NSString *)msg)

Answer 1

void append(NSString *msg) is a C function. Unlike Objective-C methods, C functions are called using parentheses rather than the Objective-C bracket notation. C functions are often seen in iOS in lower-level components and frameworks, such as the graphics libraries.

-(void) append:(NSString *)msg is an instance method. This means, that the method must be called on an instance of whatever class it has been written into.

This differs from +(void) append:(NSString *)msg, which is a class method. This means that the method must be called on the class itself, not on any single instance of the class. Class methods are usually reserved for utility methods that are general in nature, and not instance-specific.