Go 语言切片是对数组的抽象。
Go 数组的长度不可改变,在特定场景中这样的集合就不太适用,Go中提供了一种灵活,功能强悍的内置类型切片("动态数组"),与数组相比切片的长度是不固定的,可以追加元素,在追加时可能使切片的容量增大。
要定义切片,可以将其声明为数组,而不指定大小或使用make函数创建一个
var numbers []int /* a slice of unspecified size */ /* numbers == []int{0,0,0,0,0}*/ numbers = make([]int,5,5) /* a slice of length 5 and capacity 5*/
因为切片(Slice)是数组上的抽象。 它实际上使用数组作为底层结构体.len()函数返回切片中存在的元素数量,其中cap()函数返回切片(Slice)的容量(大小),即可容纳多少个元素。
以下是解释切片(Slice)的用法的示例:
package main import "fmt" func main() { var numbers = make([]int,3,5) printSlice(numbers) } func printSlice(x []int){ fmt.Printf("len=%d cap=%d slice=%v\n",len(x),cap(x),x) }
执行返回:
len = 3 cap = 5 slice = [0 0 0]
如果缺省情况下声明没有输入切片,则将其初始化为nil。 其长度和容量为零。
以下是一个示例:
package main import "fmt" func main() { var numbers []int printSlice(numbers) if(numbers == nil){ fmt.Printf("slice is nil") } } func printSlice(x []int){ fmt.Printf("len = %d cap = %d slice = %v\n", len(x), cap(x),x) }
执行返回:
len = 0 cap = 0 slice = [] slice is nil
切片(Slice)允许指定下界和上界,以使用[lower-bound:upper-bound]获取它的子切片。 以下是示例:
package main import "fmt" func main() { /* create a slice */ numbers := []int{0,1,2,3,4,5,6,7,8} printSlice(numbers) /* print the original slice */ fmt.Println("numbers ==", numbers) /* print the sub slice starting from index 1(included) to index 4(excluded)*/ fmt.Println("numbers[1:4] ==", numbers[1:4]) /* missing lower bound implies 0*/ fmt.Println("numbers[:3] ==", numbers[:3]) /* missing upper bound implies len(s)*/ fmt.Println("numbers[4:] ==", numbers[4:]) numbers1 := make([]int,0,5) printSlice(numbers1) /* print the sub slice starting from index 0(included) to index 2(excluded) */ number2 := numbers[:2] printSlice(number2) /* print the sub slice starting from index 2(included) to index 5(excluded) */ number3 := numbers[2:5] printSlice(number3) } func printSlice(x []int){ fmt.Printf("len = %d cap = %d slice = %v\n", len(x), cap(x),x) }
执行返回:
len = 9 cap = 9 slice = [0 1 2 3 4 5 6 7 8] numbers == [0 1 2 3 4 5 6 7 8] numbers[1:4] == [1 2 3] numbers[:3] == [0 1 2] numbers[4:] == [4 5 6 7 8] len = 0 cap = 5 slice = [] len = 2 cap = 9 slice = [0 1] len = 3 cap = 7 slice = [2 3 4]
切片(Slice)允许使用append()函数增加切片的容量(大小)。使用copy()函数,将源切片的内容复制到目标切片。
以下是示例:
package main import "fmt" func main() { var numbers []int printSlice(numbers) /* append allows nil slice */ numbers = append(numbers, 0) printSlice(numbers) /* add one element to slice*/ numbers = append(numbers, 1) printSlice(numbers) /* add more than one element at a time*/ numbers = append(numbers, 2,3,4) printSlice(numbers) /* create a slice numbers1 with double the capacity of earlier slice*/ numbers1 := make([]int, len(numbers), (cap(numbers))*2) /* copy content of numbers to numbers1 */ copy(numbers1,numbers) printSlice(numbers1) } func printSlice(x []int){ fmt.Printf("len=%d cap=%d slice=%v\n",len(x),cap(x),x) }
执行返回:
len = 0 cap = 0 slice = [] len = 1 cap = 2 slice = [0] len = 2 cap = 2 slice = [0 1] len = 5 cap = 8 slice = [0 1 2 3 4] len = 5 cap = 16 slice = [0 1 2 3 4]