[Yugong Series] July 2022 Go Teaching Course 021-Slicing Operation of Go Containers

---

一、切片操作

1.切片

切片和数组类似,are data sets.和数组不同的是,A slice is a piece of contiguous space of dynamically allocated size.

2.切片的使用

2.1 切片的格式

var 变量名 []T //T 表示切片类型.

相关案例：

package main

import "fmt"

func main()  {
    
	// 声明整型切片
	var numList []int

	// 声明字符串切片
	var strList []string

	// 声明一个空切片, {} Indicates that memory has been allocated,But the elements inside the slice are empty
	var numListEmpty = []int{
    }

	// 输出3个切片
	fmt.Println(numList, strList, numListEmpty)

	// 输出3个切片大小
	fmt.Println(len(numList), len(strList), len(numListEmpty))

	// Slicing determines whether the result is empty
	fmt.Println(numList == nil)
	fmt.Println(strList == nil)
	fmt.Println(numListEmpty == nil)
}

2.2 make() Function definition element

//T ： The type of elements in the slice;
//size ： Indicates how many elements are allocated for this type;
//cap : 预分配的元素数量,After this value is set, it has no effect size, Represents space allocated in advance,Setting it is mainly used to reduce dynamic expansion,造成的性能问题.
make( []T, size, cap )

相关案例：

package main

import "fmt"

func main() {
    
	a := make([]int, 10)
	b := make([]int, 10, 20)

	fmt.Println(a, b)
	fmt.Println(len(a), len(b))
}

3.append() The function adds elements

Go 语言中的内置函数 append() 可以为切片动态添加元素, 案例如下：

package main

import "fmt"

func main() {
    
	// Declare a slice of type string
	var strList []string

	// Cyclic dynamic direction strList 切片中添加 20 个元素,and print the relevant parameters
	for i := 0; i < 10; i++ {
    
		line := fmt.Sprintf("愚公 %d", i)
		strList = append(strList, line)

		fmt.Printf("len: %d, cap: %d, pointer: %p, content: %s\n", len(strList), cap(strList), strList, strList[i])
	}

	// 添加切片
	list := []string{
    "愚公 10", "愚公 11"}
	// list 后面的 ... 表示将 list 整个添加到 strList 切片中
	strList = append(strList, list...)

	fmt.Println(strList)
}

4.切片截取

slice [开始位置:结束位置]

• slice 表示切片.
• The start and end positions correspond to the subscripts of the target slice.

相关案例：

package main

import "fmt"

func main() {
    

	// 添加切片
	list := []string{
    "愚公 10", "愚公 11", "愚公 12"}
	// list 后面的 ... 表示将 list 整个添加到 strList 切片中
	fmt.Println(list, list[1:2])
}

package main

import "fmt"

func main() {
    

	// 添加切片
	list := []string{
    "愚公 10", "愚公 11", "愚公 12"}
	// list 后面的 ... 表示将 list 整个添加到 strList 切片中
	fmt.Println(list, list[1:2], list[1:], list[:2], list[:])
}

• If you do not fill in the end position,如 list[1:], It means from subscript 1 to the end of the array.
• If you do not fill in the starting position,如 list[:2],则表示从 0 到下标 2的位置.
• If the start position and end position are not filled in,如 list[:], will generate a slice identical to the original slice.

5.切片复制

copy( 原切片, 目标切片 []T) int

相关案例：

package main

import "fmt"

func main() {
    
	// 设置元素数量为 10
	const count = 10

	// 源分片
	list1 := make([]int, count)

	// Assign a value to the source shard
	for i := 0; i < count; i++ {
    
		list1[i] = i
	}

	// target shard
	list2 := make([]int, count)

	// 将 srcSlice The shard's data is copied to destSlice 中
	copy(list2, list1)

	fmt.Println(list1)
	fmt.Println(list2)
}

6.切片删除

Go The language does not provide a specific function to remove elements from a slice,可以利用appendTo achieve slice splicing to delete.

package main

import "fmt"

func main() {
    
	// Declare a slice of type string
	arr := []string{
    "1", "2", "3", "4", "5", "6", "7", "8", "9", "10"}

	// Print the elements before and after the deletion position, arr[:index] Represents the previous part of the data of the removed element,arr[index+1:] Represents the data behind the removed element
	fmt.Println(arr[:1], arr[2:])

	// Concatenate the elements before and after the deletion point
	arr = append(arr[:1], arr[2:]...)

	fmt.Println(arr)
}