golang学习之指针、内存分配
1 func pointer_test() {2 //空指针，输出为nil
3 var p *int
4 fmt.Printf("p: %v\n", p)
5 //指向局部变量，变量值初始为0
6 var i int
7 p = &i
8 fmt.Printf("p: %v,%v\n", p, *p)
9 //通过指针修改变量数值
10 *p = 8
11 fmt.Printf("p: %v,%v\n", p, *p)
12 //数组的初始化及输出
13 m := int{3, 4, 5}
14 fmt.Printf("m:%v--%v,%v,%v\n", m, m, m, m)
15 //指针数组的初始化及输出
16 //j, k, l := 3, 4, 5
17 //x := *int{&j, &k, &l}
18 x := *int{&m, &m, &m}
19 fmt.Printf("x:%v,%v,%v\n", x, x, x)
20 fmt.Printf("*x:%v,%v,%v\n", *x, *x, *x)
21
22 var n *int
23 n = x
24 fmt.Printf("n:%v,%v,%v\n", n, n, n)
25 //指向数组的指针，也即二级指针的使用
26 y := []**int{&x}
27 fmt.Printf("y:%v,%v\n", y, y)
28 fmt.Printf("*y:%v\n", *y)
29 fmt.Printf("*y[][]:%v,%v,%v\n", *y, *y, *y)
30 /*
31 *X -> v
32 X ->
33 []X -> ...
34 *X ->
35 | | |
36 j k l
37 []**X -> ...
38 | ... |
39 ->j
40 ->k
41 ->l
42 */
43 }
44
45 type Student struct {
46 namestring
47 >
48 score uint
49 }
50
51 func memery_test() {
52 //new分配出来的数据是指针形式
53 p := new(Student)
54 p.name = "China"
55 p.id = 63333
56 p.score = 99
57 fmt.Println(*p)
58 //var定义的变量是数值形式
59 var st Student
60 st.name = "Chinese"
61 st.id = 666333
62 st.score = 100
63 fmt.Println(st)
64 //make分配slice、map和channel的空间，并且返回的不是指针
65 var ptr *[]Student
66 fmt.Println(ptr) //ptr == nil
67 ptr = new([]Student) //指向一个空的slice
68 fmt.Println(ptr)
69 *ptr = make([]Student, 3, 100)
70 fmt.Println(ptr)
71 stu := []Student{{"China", 3333, 66}, {"Chinese", 4444, 77}, {"Chince", 5555, 88}}
72 fmt.Println(stu)
73 }
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