go defer 

1     conn, err := websocket.Upgrade(w, req, w.Header(), bufSize, bufSize)
2     if err != nil {
3         code = errWSUpgradeFailed
4         msg = err.Error()
5         return
6     }
7     defer conn.Close()

defer conn.Close() 要放在判err之后，因为err时conn为nil，然后nil.Close()会使程序出错，甚至直接panic崩调

    code := Success
    msg := ""
    var response responseJSON
    defer func() {
        writeResponse(msg, response, w, code)
    }()

defer执行匿名函数

  1 package main
  2 import "fmt"
  3 func f1() (result int) {
  4     println("-------------------------------")
  5     defer func() {
  6         result++
  7     }()
  8     return 0
  9 }
 10 func f2() (r int) {
 11     println("-------------------------------")
 12      t := 5
 13      defer func() {
 14        t = t + 5
 15      }()
 16      return t
 17 }
 18 func f3() (r int) {
 19     println("-------------------------------")
 20     defer func(r int) {
 21           r = r + 5
 22     }(r)
 23     return 1
 24 }
 25 func f4() (r int) {
 26     println("-------------------------------")
 27     r=100
 28     return
 29 }
 30 func f5() (r1 int,r2 interface{},r3 string) {
 31     println("-------------------------------")
 32     return
 33 }
 34 func f6() (r1 int) {
 35     println("-------------------------------")
 36     defer func() {
 37         if r1==100 {
 38             println("r1==100")
 39         }
 40     }()
 41     r1=100
 42     return
 43 }
 44 func f7() (r1 int) {
 45     println("-------------------------------")
 46     r1=100
 47     return 1
 48 }
 49 func f8() (r1 int) {
 50     println("-------------------------------")
 51     r1=100
 52     defer func() {
 53         r1++;
 54     }()
 55     return 1
 56 }
 57 func f9() (r1 int) {
 58     println("-------------------------------")
 59     defer func(r int) {
 60         r++
 61     }(r1)
 62     return
 63 }
 64 func f10() (r interface{}) {
 65     println("-------------------------------")
 66     r=1
 67     defer func(a interface{}) {
 68         fmt.Println("a:",a)
 69         fmt.Println("r:",r)
 70         a=100
 71         fmt.Println("a:",a)
 72         fmt.Println("r:",r)
 73     }(r)
 74     return
 75 }
 76 func f11() (r interface{}) {
 77     println("-------------------------------")
 78     r=1
 79     defer func(a interface{}) {
 80         fmt.Println("a:",a)
 81         fmt.Println("r:",r)
 82         a=100
 83         fmt.Println("a:",a)
 84         fmt.Println("r:",r)
 85     }(r)
 86     r=2
 87     defer func(a interface{}) {
 88         fmt.Println("second a:",a)
 89         fmt.Println("second r:",r)
 90         a=200
 91         fmt.Println("second a:",a)
 92         fmt.Println("second r:",r)
 93     }(r)
 94     return
 95 }
 96 func f12() (r interface{}) {
 97     println("-------------------------------")
 98     r=1
 99     defer func(a interface{}) {
100         fmt.Println("a:",a)
101         fmt.Println("r:",r)
102         a=100
103         fmt.Println("a:",a)
104         fmt.Println("r:",r)
105     }(r)
106     r=2
107     defer func(a interface{}) {
108         fmt.Println("second a:",a)
109         fmt.Println("second r:",r)
110         a=200
111         fmt.Println("second a:",a)
112         fmt.Println("second r:",r)
113     }(r)
114     r=3
115     return
116 }
117 func f13() (a interface{},b interface{}) {
118     println("-------------------------------")
119     return 1,2
120 }
121 func f14() map[string]string{
122     println("-------------------------------")
123     a:=map[string]string{"a":"b"}
124     defer func(mp map[string]string) {
125         mp["a"]="c"
126     }(a)
127     return a
128 }
129 func f15() string{
130     println("-------------------------------")
131     a:="a"
132     defer func(mp string) {
133         mp="b"
134     }(a)
135     return a
136 }
137 func f16() []byte{
138     println("-------------------------------")
139     a:=[]byte("a")
140     defer func(mp []byte) {
141         mp=[]byte("b")
142     }(a)
143     return a
144 }
145 func f17() chan int{
146     println("-------------------------------")
147     a:=make(chan int,10)
148     defer func(mp chan int) {
149         mp<-1
150     }(a)
151     return a
152 }
153 func main() {
154     println(f1())
155     println(f2())
156     println(f3())
157     println(f4())
158     a,b,c:=f5()
159     fmt.Println(a,b,c)
160     println(f6())
161     println(f7())
162     println(f8())
163     println(f9())
164     fmt.Println(f10())
165     fmt.Println(f11())
166     fmt.Println(f12())
167     e,f:=f13()
168     fmt.Println(e,f)
169     fmt.Println(f14())
170     fmt.Println(f15())
171     fmt.Println(string(f16()))
172     fmt.Println(len(f17()))
173 }
测试
 1 -------------------------------
 2 1
 3 -------------------------------
 4 5
 5 -------------------------------
 6 1
 7 -------------------------------
 8 100
 9 -------------------------------
10 0 <nil> 
11 -------------------------------
12 r1==100
13 100
14 -------------------------------
15 1
16 -------------------------------
17 2
18 -------------------------------
19 0
20 -------------------------------
21 a: 1
22 r: 1
23 a: 100
24 r: 1
25 1
26 -------------------------------
27 second a: 2
28 second r: 2
29 second a: 200
30 second r: 2
31 a: 1
32 r: 2
33 a: 100
34 r: 2
35 2
36 -------------------------------
37 second a: 2
38 second r: 3
39 second a: 200
40 second r: 3
41 a: 1
42 r: 3
43 a: 100
44 r: 3
45 3
46 -------------------------------
47 1 2
48 -------------------------------
49 map[a:c]
50 -------------------------------
51 a
52 -------------------------------
53 a
54 -------------------------------
55 1
结果

defer会从下往上执行，若return时没到达的defer不执行，

非匿名函数

func(a interface{},b interface{}) (c interface{},d interfacd{}) {

c=3

d=4

return

return 1,2

}

c和d在进入函数时定义，一旦return，c和d的值都会返回，如果return 1,2，则1,2的值会赋给c，d，return时要么都不赋值，要么都赋值，不能只赋部分

 

对于匿名函数func(a interface{}) {

 a=1

}(r)

表示将r传入函数作为a的值，除了chan和map，别的一定是复制传入(interface{},[]byte,etc)，不会传入指针，而且a的值是运行函数时r的值

posted @ 2017-04-05 16:20  cdongyang  阅读(315)  评论(0)  编辑  收藏  举报