Ruby in a Nutshell

Specifying Blocks with Method Calls

Methods may be called with blocks of code specified that will be called from within the method.

method_call {[|[variable[, variable...]]|] code}
method_call do [|[variable[, variable...]]|] code end

Calls a method with blocks specified. The code in the block is executed after a value is passed from the method to the block and assigned to the variable (the block’s argument) enclosed between ||.

A block introduces its own scope for new local variables. The local variables that appear first in the block are local to that block. The scope introduced by a block can refer local variables of outer scope; on the other hand, the scope introduced by class, module and def statement can’t refer outer local variables.

The form {...} has a higher precedence than do ... end. The following:

identifier1 identifier2 {|varizable| code}

actually means:

identifier1(identifier2 {|variable| code})

On the other hand:

identifier1 identifier2 do |variable| code end

actually means:

identifier1(identifier2) do |variable| code end