Programming Groovy 2

Closure Delegation

Closures in Groovy go far beyond being simple anonymous methods; they have some powerful capabilities, as we’ll see in the rest of this chapter. Groovy closures support method delegation, and provide capabilities for method-dispatching—much like JavaScript’s support for prototypal inheritance. Let’s understand the magic behind this and how to put this to good use.

Three properties of a closure—this, owner, and delegate—determine which object handles a method call from within a closure. Generally, the delegate is set to owner, but changing it lets us exploit Groovy for some really good metaprogramming capabilities. Let’s examine these properties for closures: