示例代码
package mainimport ( "fmt")func main() { a := []string{"A", "B", "C", "D", "E"} a = nil fmt.Println(a, len(a), cap(a))}result: [] 0 0 说明: a 是 一个nil 的slice
package mainimport ( "fmt")func main() { a := []string{"A", "B", "C", "D", "E"} a = a[:0] //空的slice fmt.Println(a, len(a), cap(a))}result [] 0 5 说明 a是长度是0的emtpy slice
nil slice vs empty slice
- nil slice 的长度len和容量cap都是0
- empty slice的长度是0, 容量是由指向底层数组决定
- empty slice != nil
- nil slice的pointer 是nil, empty slice的pointer是底层数组的地址
slice的底层表示形式
[pointer] [length] [capacity]nil slice: [nil][0][0]empty slice: [addr][0][0] // pointer是底层数组的地址创建nil slice和empty slice
package mainimport ( "fmt")func main() { var nilSlice []string emptySlice0 := make([]int, 0) var emptySlice1 = []string{} fmt.Printf("\nNil:%v Len:%d Capacity:%d", nilSlice == nil, len(nilSlice), cap(nilSlice)) fmt.Printf("\nnil:%v Len:%d Capacity:%d", emptySlice0 == nil, len(emptySlice0), cap(emptySlice0)) fmt.Printf("\nnil:%v Len:%d Capacity:%d", emptySlice1 == nil, len(emptySlice1), cap(emptySlice1))}make slice 规则
package mainimport "fmt"func main() { s1 := make([]int, 5) fmt.Printf("The length of s1: %d\n", len(s1)) fmt.Printf("The capacity of s1: %d\n", cap(s1)) fmt.Printf("The value of s1: %d\n", s1) s2 := make([]int, 5, 8) fmt.Printf("The length of s2: %d\n", len(s2)) fmt.Printf("The capacity of s2: %d\n", cap(s2)) fmt.Printf("The value of s2: %d\n", s2)}make 初始化slice
- 第一个参数表示长度
- 第二个参数表示容量
- make函数初始化切片时，如果不指明其容量，那么它就会和长度一致
links
- Arrays, slices (and strings): The mechanics of 'append' – The Go Blog
- go – The zero value of a slice is not nil – Stack Overflow
- A Tour of Go
- https://time.geekbang.org/col…
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文章来源：智云一二三科技
文章标题：golang nil slice & empty slice 笔记
文章地址：https://www.zhihuclub.com/4885.shtml
