在上篇《
Groovy解惑——closure中的delegate》中，我帮大家讲解了delegate是什么以及其作用。
本篇将讲解一下closure中的owner，以及this,delegate以及owner三者间的关系。
先让我们来看个例子：
class OwnerDemo {
def outerClosure = {
println "the owner of outerClosure: " + owner
def innerClosure = {
println "the owner of innerClosure: " + owner
def innestClosure = {
println "the owner of innestClosure: " + owner
}
innestClosure()
}
innerClosure()
}
}
def ownerDemo = new OwnerDemo()
ownerDemo.outerClosure()
运行结果：
the owner of outerClosure: OwnerDemo@eccfe7
the owner of innerClosure: OwnerDemo$_closure1@4745cf
the owner of innestClosure: OwnerDemo$_closure1_closure2@109dcbb
注意：OwnerDemo$_closure1指的是outerClosure的类名，而OwnerDemo$_closure1_closure2指的是innerClosure的类名
通过这个例子，大家就清楚了，
closure的owner引用的是该closure的‘拥有者’那么this, delegate以及owner有什么关系呢？
隐式变量delegate的默认值为owner，
如果closure没有‘嵌套’在其他closure中，那么该closure的owner的值为this；
否则该closure的owner引用的是‘直接包含’该closure的closure让我们用事实来说话吧：
class OwnerDemo {
def outerClosure = {
println "the owner of outerClosure: " + owner
println "the delegate of outerClosure: " + delegate
println "this in the outerClosure: " + this
def innerClosure = {
println "the owner of innerClosure: " + owner
println "the delegate of innerClosure: " + delegate
println "this in the innerClosure: " + this
def innestClosure = {
println "the owner of innestClosure: " + owner
println "the delegate of innestClosure: " + delegate
println "this in the innestClosure: " + this
}
println "innestClosure: " + innestClosure
innestClosure()
}
println "innerClosure: " + innerClosure
innerClosure()
}
}
def ownerDemo = new OwnerDemo()
def outerClosure = ownerDemo.outerClosure
println "outerClosure: " + outerClosure
outerClosure()
运行结果：
outerClosure: OwnerDemo$_closure1@10cc9b4
the owner of outerClosure: OwnerDemo@8e7f54
the delegate of outerClosure: OwnerDemo@8e7f54
this in the outerClosure: OwnerDemo@8e7f54
innerClosure: OwnerDemo$_closure1_closure2@1eb1db2
the owner of innerClosure: OwnerDemo$_closure1@10cc9b4
the delegate of innerClosure: OwnerDemo$_closure1@10cc9b4
this in the innerClosure: OwnerDemo@8e7f54
innestClosure: OwnerDemo$_closure1_closure2_closure3@12a78ee
the owner of innestClosure: OwnerDemo$_closure1_closure2@1eb1db2
the delegate of innestClosure: OwnerDemo$_closure1_closure2@1eb1db2
this in the innestClosure: OwnerDemo@8e7f54
大家可以从其中值的关系看出this, delegate以及owner三者的关系与我们之前所说的相符 :)
连夜连发2篇文章以回报‘蛟龙居’的常客 :)附：
朝花夕拾——Groovy & Grails
posted on 2007-12-23 01:43
山风小子 阅读(2966)
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Groovy & Grails