How to check if a map contains a key in Go (Golang)

Below is the format to check if a key exists in the map

val, ok := mapName[key]

There are two cases

If the key existsvalvariable be the value of the key in the map andokvariable will be true
If the key doesn’t existvalvariable will be default zero value of value type andokvariable will be false

Let’s see an example

package main
import "fmt"
func main() {
//Declare
employeeSalary := make(map[string]int)
//Adding a key value
employeeSalary["Tom"] = 2000
fmt.Println("Key exists case")
val, ok := employeeSalary["Tom"]
fmt.Printf("Val: %d, ok: %t\n", val, ok)
fmt.Println("Key doesn't exists case")
val, ok = employeeSalary["Sam"]
fmt.Printf("Val: %d, ok: %t\n", val, ok)
}

Output

Key exists case
Val: 2000, ok: true
Key doesn't exists case
Val: 0, ok: false

In the above program when a key exists thenvalvariable is set to the actual value which is 2000 here andokvariable is true. When the key doesn’t exist thevalvariable is set to 0 which is the default zero value of int andokvariable is false. Thisokvariable is the best way to check if the key exists in a map or not

In case we only want to check if a key is present and val is not needed, then blank identifier i.e “_” can be used in place of val.

_, ok = employeeSalary["Sam"]

Also, check out our Golang advance tutorial Series – Golang Advance Tutorial

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