処理の差し替え

処理の差し替え.groovy

class Hello {void hello(){println "1"}}
def a = new Hello()
def b = new Hello()

b.metaClass.hello = { println "2" } 
a.hello()
b.hello()

a.metaClass.hello = {b.metaClass.hello}
a.hello()
b.hello()

a.metaClass.hello = { println "3" } 
a.hello()
b.hello()
a.&hello()

結果

1
2
2
3
2
1