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Golang method to determine whether key exists in map

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2019-12-13 14:20:3412072browse

Golang method to determine whether key exists in map

The method code for golang to determine whether the key exists in the map:

if _, ok := map[key]; ok {
//存在
}

In addition, golang does not provide a method to determine whether the item is in the array. If it is frequently used in the program For this kind of judgment, the array can be converted into a map with the members in the array as keys and then judged using the above method, which will improve the efficiency of judgment.

Example:

package main

import "fmt"

func main() {
	//声明并初始化一个map,key是int64类型,value是string类型
	myMap := make(map[int64]string)

	myMap[1] = "value1"
	myMap[2] = "value2"
	myMap[5] = "value5"
	myMap[6] = "value6"

	//声明一个int64数组,然后遍历数组,num是数组中的元素,下划线_代表元素的下标位置
	for _, num := range []int64{1, 2, 3, 4, 5, 6} {
		//不关心数组中的value,用下划线代替
		//一般都习惯用ok变量表示是否包含,也可以用别的变量名字
		if _, ok := myMap[num]; ok {
			fmt.Printf("myMap中包含key:%d \n", num, )
		} else {
			fmt.Printf("myMap中不包含key:%d\n", num)
		}
	}

	fmt.Println("=================分割线=======================")

	for _, num := range []int64{1, 2, 3, 4, 5, 6} {
		//如果包含key,想知道value,就把返回值赋给一个变量,这儿用变量v
		//这儿用变量s表示是否包含指定的key
		if v, s := myMap[num]; s {
			fmt.Printf("myMap中包含key:%d,value值为:%s\n", num, v)
		} else {
			fmt.Printf("myMap中不包含key:%d\n", num)
		}
	}
}

Output after running:

myMap中包含key:1 
myMap中包含key:2 
myMap中不包含key:3
myMap中不包含key:4
myMap中包含key:5 
myMap中包含key:6 
=================分割线=======================
myMap中包含key:1,value值为:value1
myMap中包含key:2,value值为:value2
myMap中不包含key:3
myMap中不包含key:4
myMap中包含key:5,value值为:value5
myMap中包含key:6,value值为:value6

For more golang knowledge, please pay attention to the go language tutorial column.

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