基本概念
- 与数组很相似，但是Slices长度是可变的，操作方式与Python的list类型相似，例如新增一个元素。
- 区别在于Slices通过指针指向数组，所以Slices是引用类型(Reference type)
- 如果将slice复制给其他元素，则二者均是指向同一个底层数组
- 对于函数传参时，也会指向统一底层数组
- 切片可以由数组一部分进行截取
- len返回的是长度
- cap返回的是容量
- 以下示例说明array的长度和容量是相同的，而对于slice，len是实际数组的长度，cap则大于len
1
2
3
4
5
6
7
8
9
10
11
| package main
import "fmt"
func main() {
var my_array [100]int
my_slice := my_array[0:50]
fmt.Printf("Slice len = %d\n", len(my_slice))
fmt.Printf("Slice cap = %d\n", cap(my_slice))
}
|
输出结果
1
2
| Slice len = 50
Slice cap = 100
|
常用操作
通过make定义slice
1
| slice := make([]int, 10)
|
关于make
在《Effective Go》中的解释为
The built-in function make takes a type T, which must be a slice, map or channel type, optionally followed by a type-specific list of expressions.
It returns a value of type T (not *T).
The memory is initialized as described in the section on initial values.
对于上述描述的需要理解的是：
- make主要用于创建切片(slice)，以及我们后面要讲到的Maps和Channel三种类型
- 返回的值是T，而非*T(即指针T)
- 内存初始化按照初始值进行
参考资料
截取指定元素
- 只支持正数，无法像Python一样使用负数反向截取
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
| package main
import "fmt"
func main() {
a := [...]int{1, 2, 3, 4, 5}
s1 := a[2:4]
fmt.Printf("s1 = %d\n", s1)
fmt.Printf("s1 = %v\n", s1)
s2 := a[1:5]
fmt.Printf("s2 = %v\n", s2)
s3 := a[:]
fmt.Printf("s3 = %v\n", s3)
s4 := a[:4]
fmt.Printf("s4 = %v\n", s4)
s5 := s2[:]
fmt.Printf("s5 = %v\n", s5)
s6 := a[2:4:5]
fmt.Printf("s6 = %v\n", s6)
}
|
输出结果
1
2
3
4
5
6
7
| s1 = [3 4]
s1 = [3 4]
s2 = [2 3 4 5]
s3 = [1 2 3 4 5]
s4 = [1 2 3 4]
s5 = [2 3 4 5]
s6 = [3 4]
|
- slice越界后提示Error: “throw: index out of range”
1
2
3
4
5
6
7
8
9
10
| package main
func main() {
var array [100]int
slice := array[0:99]
slice[98] = 1 3
// ERROR: index out of range
slice[99] = 2 4
}
|
Slice扩展(append)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
| package main
import "fmt"
func main() {
s0 := []int{0, 0}
s1 := append(s0, 2)
s2 := append(s1, 3, 5, 7)
// Append slice instead of value, add ...
s3 := append(s2, s0...)
fmt.Println("s0 = %v", s0)
fmt.Println("s1 = %v", s1)
fmt.Println("s2 = %v", s2)
fmt.Println("s3 = %v", s3)
}
|
如果追加的是slice，在后面加三个点，普通值直接追加即可
1
2
3
4
| s0 = %v [0 0]
s1 = %v [0 0 2]
s2 = %v [0 0 2 3 5 7]
s3 = %v [0 0 2 3 5 7 0 0]
|
Slice复制(Copy)
- slice操作，copy，将源拷贝至目标，并且返回拷贝的数量
copy( destSlice, srcSlice []T) int
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
| package main
import "fmt"
func main() {
var a = [...]int{0, 1, 2, 3, 4, 5, 6, 7}
var s = make([]int, 6)
fmt.Printf("initial a = %v\n", a)
fmt.Printf("initial s = %v\n", s)
n1 := copy(s, a[0:])
fmt.Printf("n1 = %v\n", n1)
fmt.Printf("a = %v\n", a)
fmt.Printf("s = %v\n", s)
fmt.Printf("s[2:] = %v\n", s[2:])
n2 := copy(s, s[2:])
fmt.Printf("n2 = %v\n", n2)
fmt.Printf("a = %v\n", a)
fmt.Printf("s = %v\n", s)
}
|
输出结果
1
2
3
4
5
6
7
8
9
| initial a = [0 1 2 3 4 5 6 7]
initial s = [0 0 0 0 0 0]
n1 = 6
a = [0 1 2 3 4 5 6 7]
s = [0 1 2 3 4 5]
s[2:] = [2 3 4 5]
n2 = 4
a = [0 1 2 3 4 5 6 7]
s = [2 3 4 5 4 5]
|
老孙正经胡说