You want to be able to write your own block objects or use block objects with iOS SDK classes.

You just need to understand the basic differences between the syntax of block objects and classic C functions. These differences are explained in the Discussion section.

Block objects can either be inline or coded as independent blocks of code. Let’s start with the latter type. Suppose you have a method in Objective-C that accepts two integer values of type NSInteger and returns the difference of the two values, by subtracting one from the other, as an NSInteger:

- (NSInteger) subtract:(NSInteger)paramValue
                  from:(NSInteger)paramFrom{

  return paramFrom - paramValue;

}