Uploaded October 2012 | Updated September 2026, 2 weeks ago

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Block objects provide a way for you to create an ad hoc function body as an expression in C, and C-derived languages such as Objective-C and C++. In other languages and environments, a block object is sometimes also called a "closure". Here, they are typically referred as "blocks", unless there is scope for confusion with the standard C term for a block of code.

You use the ^ operator to declare a block variable and to indicate the beginning of a block literal. The body of the block itself is contained within {}, as shown in this example (as usual with C, ; indicates the end of the statement):

int multiplier = 7;

int (^myBlock)(int) = ^(int num) {
return num * multiplier;
};

Notice that the block is able to make use of variables from the same scope in which it was defined.

If you declare a block as a variable, you can then use it just as you would a function:

int multiplier = 5;

int (^myBlock)(int) = ^(int num) {
return num * multiplier;
};

int result = myBlock(4);

NSLog(@"result = %d", result); // will output "result = 20"

You can find more about blocks on the following web page:

developer.apple.com/library/ios/#documentation/cocoa/Conceptual/Blocks/Articles/00_Introduction.html