捕获：groovy.lang.MissingMethodException：没有方法的签名

Question

Simple code: ClosuresSyntax.groovy

{ -> item++ }
{ item -> item++ }

it cause an exception:

Caught: groovy.lang.MissingMethodException: No signature of method:  
       com.lucaslee.groovy.syntax.ClosuresSyntax$_run_closure1.call()      is applicable for argument types:
(com.lucaslee.groovy.syntax.ClosuresSyntax$_run_closure2) values: 
    [com.lucaslee.groovy.syntax.ClosuresSyntax$_run_closure2@1534f01b]     

Answer 1

Your code is the same as (note the parentheses):

{ -> item++}({ item -> item++})

The definition of both closures is fully correct. The problem is that in fact the first closure is run with the second one passed as an argument. This is exactly the same:

{ it -> it() } { println 1 }

Since you can't invoke ++ on a Closure object MissingMethodException is thrown. This will work correctly eg:

{ item -> item()++ }{ 1 }

A closure {1} is passed as an argument, invoked () and a result is incremented ++ .

To verify that closures definitions are correct, run:

def a = { -> item++ }
def b = { item -> item++ }