1. package main
    3. import (
    4.     "fmt"
    5. )
    7. func main() {
    8.     filtered := make([]*student, 10)
    9.     fmt.Printf("filtered: len=%v cap=%v \n", len(filtered), cap(filtered))
    10.     for index, val := range filtered {
    11.         fmt.Println("index: ", index, "val: ", val)
    12.     }
    13. }

    输出：

    1. filtered: len=10 cap=10
    2. index:  0 val:  <nil>
    3. index:  1 val:  <nil>
    4. index:  2 val:  <nil>
    5. index:  3 val:  <nil>
    6. index:  4 val:  <nil>
    7. index:  5 val:  <nil>
    8. index:  6 val:  <nil>
    9. index:  7 val:  <nil>
    10. index:  8 val:  <nil>
    11. index:  9 val:  <nil>

    可以看到filtered长度不为0，for循环就会遍历。不指定cap时，默认len和cap相等。

    1. package main
    3. import (
    4.     "fmt"
    5. )
    7. func main() {
    8.     filtered := make([]*student, 10)
    9.     fmt.Printf("filtered: len=%v cap=%v \n", len(filtered), cap(filtered))
    10.     for index, val := range filtered {
    11.         fmt.Println("index: ", index, "val: ", val)
    12.         filtered[index] = &student{
    13.             ID: index,
    14.             Name: fmt.Sprintf("%v", index),
    15.         }
    16.     }
    17.     fmt.Printf("filter[8]=%v, addr=%p\n", filtered[8], &filtered[8])
    18.     aa := filtered[8]
    19.     fmt.Printf("aa=%v, addr=%p\n", aa, &aa)
    21.     aa.Name = "test coderaction"
    22.     fmt.Printf("filter[8]=%v, addr=%p\n", filtered[8], &filtered[8])
    23.     fmt.Printf("aa=%v, addr=%p\n", aa, &aa)
    24. }
    26. type student struct {
    27.     ID int
    28.     Name string
    29. }
    31. func getPods() []*student {
    32.     stu1 := &student{
    33.         ID: 1,
    34.         Name: "stu1",
    35.     }
    37.     stu2 := &student{
    38.         ID: 2,
    39.         Name: "stu2",
    40.     }
    42.     return []*student{stu1, stu2}
    43. }

    输出：

    1. filtered: len=10 cap=10
    2. index:  0 val:  <nil>
    3. index:  1 val:  <nil>
    4. index:  2 val:  <nil>
    5. index:  3 val:  <nil>
    6. index:  4 val:  <nil>
    7. index:  5 val:  <nil>
    8. index:  6 val:  <nil>
    9. index:  7 val:  <nil>
    10. index:  8 val:  <nil>
    11. index:  9 val:  <nil>
    12. filter[8]=&{8 8}, addr=0xc0000a4040
    13. aa=&{8 8}, addr=0xc00009c020
    14. filter[8]=&{8 test coderaction}, addr=0xc0000a4040
    15. aa=&{8 test coderaction}, addr=0xc00009c020

    可以看到修改了aa之后，filtered[8]的内容也变掉了。

    给aa新赋值&student{}，发现filtered[8]是没有变化的：

    1. package main
    3. import (
    4.     "fmt"
    5. )
    7. func main() {
    8.     filtered := make([]*student, 10)
    9.     fmt.Printf("filtered: len=%v cap=%v \n", len(filtered), cap(filtered))
    10.     for index, val := range filtered {
    11.         fmt.Println("index: ", index, "val: ", val)
    12.         filtered[index] = &student{
    13.             ID: index,
    14.             Name: fmt.Sprintf("%v", index),
    15.         }
    16.     }
    17.     fmt.Printf("filter[8]=%v, addr=%p\n", filtered[8], &filtered[8])
    18.     aa := filtered[8]
    19.     fmt.Printf("aa=%v, addr=%p\n", aa, &aa)
    21.     aa = &student{
    22.         ID: 1001,
    23.         Name: "aaaa",
    24.     }
    25.     fmt.Printf("filter[8]=%v, addr=%p\n", filtered[8], &filtered[8])
    26.     fmt.Printf("aa=%v, addr=%p\n", aa, &aa)
    27. }
    29. type student struct {
    30.     ID int
    31.     Name string
    32. }

    可以看到aa的地址和filtered[8]不一样：

    1. filtered: len=10 cap=10
    2. index:  0 val:  <nil>
    3. index:  1 val:  <nil>
    4. index:  2 val:  <nil>
    5. index:  3 val:  <nil>
    6. index:  4 val:  <nil>
    7. index:  5 val:  <nil>
    8. index:  6 val:  <nil>
    9. index:  7 val:  <nil>
    10. index:  8 val:  <nil>
    11. index:  9 val:  <nil>
    12. filter[8]=&{8 8}, addr=0xc000090040
    13. aa=&{8 8}, addr=0xc000006030
    14. filter[8]=&{8 8}, addr=0xc000090040
    15. aa=&{1001 aaaa}, addr=0xc000006030