Groovy裏面閉包中變量符號的查找與變量定義的限制

 1 class a {
 2     def v1 = "v1 in a"
 3     static def v2 = "v2 in a"
 4     def v4 = "v4 in a"
 5     def v5 = "v5 in a"
 6     def va = "va in a"
 7     def b() {
 8         def v1 = "v1 in a.b()"
 9         def v2 = "v2 in a.b()"
10         def v4 = "v4 in a.b()"
11         def g = {
12             def v0 = "v0 in closure g"
13             def h = {
14                 //function b裏面已經定義v4 = "v4 in a.b()"因此下面這行
15                 //報錯:The current scope already contains a variable of the name v4
16                 //def v4 = "v4 in closure h"
17             }
18         }
19         def c = {
20             //下面的這行代碼報錯:The current scope already contains a variable of the name v1
21             //def v1 = "v1 in closure c"
22             println v1
23             println owner
24             println this
25             //下面這行定義v5變量正常,輸出的結果也是:v5 in closure c
26             def v5 = "v5 in closure c"
27             println  v5//v4
28             println va
29         }
30         println "***" + c.toString() + "***"
31         c()
32         
33        return "b func"
34     }
35     
36     def d = {
37         println v1;
38         println v2;
39         println v4;
40         def v5 = "v5 in closure d"
41         println v5
42     }
43     
44     def e = {
45         def v1 = "v1 in closure e"
46         def f = {
47             //下面這行代碼報錯:The current scope already contains a variable of the name v1
48             //def v1 = "v1 in closure f"
49             println v1
50             
51             //下面這行就沒錯,由於閉包e的v2是在後面定義的
52             def v2 = "v2 in closure f"
53     
54             //下面這行報錯,v3在f裏面不可見
55             //println v3
56             
57             def vf = "vf in closure f"
58         }
59         f()
60         def v2 = "v2 in closure e"
61         def v3 = "v3 in closure e"
62         
63         //在閉包e裏面vf不可見
64         //println vf
65     }
66 }
67 def test(x) {
68     println "func test start --- x:" + x
69     def v1 = 1000
70     def v2 = 2000
71     def v3 = 3000
72     
73     x()
74     println "func test--- end:"
75 }
76 test(new a().d)
77 println "--------------"
78 //println new a().v4
79 println new a().b()
80 new a().e()
81 
82 
83 /*
84 經過上面的測試代碼能夠看出:
85 1.在閉包a裏面定義的閉包b,那麼b中定義的變量不能和和閉包a裏面定義的變量名字相同.
86 2.在函數a裏面定義的閉包b,那麼b中定義的變量不能和和函數a裏面定義的變量名字相同.
87 3.由此也能夠推導出:在函數a裏面定義閉包b,在閉包b裏面定義閉包c,那麼c中定義
88 的變量也不能和函數a中定義的變量名字相同,對於任意多層閉包嵌套也是如此
89 在閉包裏面的符號查找方面:
90     首先在閉包裏面查找,若是閉包裏面沒有定義,則有兩種狀況(假設delegate策略是Closure.OWNER_FIRST,其它策略是同樣的):
91         1.若是這個閉包的外層是函數,則如今函數裏面查找,若是函數裏面也沒有定義,則進入delegate策略即在owner裏面查找,
92         若是owner裏面沒有,則在delegate裏面查找,ruguo delegate裏面沒有就報錯
93         2.若是這個閉包沒外層不是函數,則直接進入delegate策略即在owner裏面查找,若是owner裏面沒有,則在delegate裏面查找
94         若是delegate裏面沒有就報錯.
95 
96 */