Objective-C Programming: The Big Nerd Ranch Guide

28 Blocks

A block is a chunk of code. Here is a block:

^​{​
 ​ ​ ​ ​N​S​L​o​g​(​@​"​T​h​i​s​ ​i​s​ ​a​n​ ​i​n​s​t​r​u​c​t​i​o​n​ ​w​i​t​h​i​n​ ​a​ ​b​l​o​c​k​.​"​)​;​
}​

It looks like a C function; it is a set of instructions inside curly braces. It does not, however, have a name. Instead, the caret (^) identifies this bit of code as a block.

Like a function, a block can take arguments and return values. Here is another block:

^​(​d​o​u​b​l​e​ ​d​i​v​i​d​e​n​d​,​ ​d​o​u​b​l​e​ ​d​i​v​i​s​o​r​)​ ​{​
 ​ ​ ​ ​d​o​u​b​l​e​ ​q​u​o​t​i​e​n​t​ ​=​ ​d​i​v​i​d​e​n​d​ ​/​ ​d​i​v​i​s​o​r​;​
 ​ ​ ​ ​r​e​t​u​r​n​ ​q​u​o​t​i​e​n​t​;​
}​

This block takes two doubles as arguments and returns a double.

You can pass a block as an argument ...