groovy解惑——closure中的owner
在上篇《
groovy解惑——closure中的delegate
》中，我幫大家講解了delegate是什麼以及其作用。
本篇將講解一下closure中的owner，以及this,delegate以及owner三者間的關係。
先讓我們來看個例子：
class
ownerdemo
innestclosure()
}innerclosure()}}
def ownerdemo
=new
ownerdemo()
ownerdemo.outerclosure()
執行結果：
the owner of outerclosure: ownerdemo@eccfe7
the owner of innerclosure: ownerdemo$_closure1@4745cf
the owner of innestclosure: ownerdemo$_closure1_closure2@109dcbb
注意：ownerdemo$_closure1指的是outerclosure的類名，而ownerdemo$_closure1_closure2指的是innerclosure的類名
通過這個例子，大家就清楚了，closure的owner引用的是該closure的『擁有者』
那麼this, delegate以及owner有什麼關係呢？
隱式變數delegate的預設值為owner，
如果closure沒有『巢狀』在其他closure中，那麼該closure的owner的值為this；
否則該closure的owner引用的是『直接包含』該closure的closure
讓我們用事實來說話吧：
class
ownerdemo
println
"innestclosure: "+
innestclosure
innestclosure()
}println
"innerclosure: "+
innerclosure
innerclosure()}}
def ownerdemo
=new
ownerdemo()
def outerclosure
=ownerdemo.outerclosure
println
"outerclosure: "+
outerclosure
outerclosure()
執行結果：
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
大家可以從其中值的關係看出this, delegate以及owner三者的關係與我們之前所說的相符 :)
』的常客 :)
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