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How to Check if a Key Exists in a Map in Go

How to Check if a Key Exists in a Map in Go ?

Answer

To check if a key exists in a map in Go, you can use the value, ok idiom. This idiom checks if a key is present in the map and returns a boolean value indicating its presence.


✐ Examples

1 Checking if a Key Exists Using value, ok Idiom

We can check if a key exists in a map in Go using the value, ok idiom, which checks if a key is present in the map and returns a boolean value indicating its presence.

For example,

  1. We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
  2. We use the value, ok idiom to check for a specific key in the map. The idiom returns the value associated with the key and a boolean indicating if the key is present in the map.
  3. We print the result to the console using the fmt.Printf function.

Go Program

package main

import "fmt"

func main() {
    // Declare and initialize a map
    myMap := map[string]int{
        "one": 1,
        "two": 2,
        "three": 3,
    }

    // Check if a key exists using value, ok idiom
    if value, ok := myMap["two"]; ok {
        fmt.Printf("Key 'two' exists with value: %d\n", value)
    } else {
        fmt.Println("Key 'two' does not exist.")
    }
}

Output

Key 'two' exists with value: 2

2 Checking if a Key Does Not Exist Using value, ok Idiom

We can check if a key does not exist in a map in Go using the value, ok idiom, which checks if a key is present in the map and returns a boolean value indicating its presence.

For example,

  1. We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
  2. We use the value, ok idiom to check for a specific key in the map. The idiom returns the value associated with the key and a boolean indicating if the key is present in the map.
  3. We print the result to the console using the fmt.Printf function.

Go Program

package main

import "fmt"

func main() {
    // Declare and initialize a map
    myMap := map[string]int{
        "one": 1,
        "two": 2,
        "three": 3,
    }

    // Check if a key does not exist using value, ok idiom
    if value, ok := myMap["four"]; ok {
        fmt.Printf("Key 'four' exists with value: %d\n", value)
    } else {
        fmt.Println("Key 'four' does not exist.")
    }
}

Output

Key 'four' does not exist.

3 Checking Multiple Keys Using value, ok Idiom

We can check if multiple keys exist in a map in Go using the value, ok idiom, which checks if each key is present in the map and returns a boolean value indicating its presence.

For example,

  1. We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
  2. We use the value, ok idiom to check for multiple keys in the map. The idiom returns the value associated with each key and a boolean indicating if the key is present in the map.
  3. We print the results to the console using the fmt.Printf function.

Go Program

package main

import "fmt"

func main() {
    // Declare and initialize a map
    myMap := map[string]int{
        "one": 1,
        "two": 2,
        "three": 3,
    }

    // Check if multiple keys exist using value, ok idiom
    if value, ok := myMap["one"]; ok {
        fmt.Printf("Key 'one' exists with value: %d\n", value)
    } else {
        fmt.Println("Key 'one' does not exist.")
    }

    if value, ok := myMap["four"]; ok {
        fmt.Printf("Key 'four' exists with value: %d\n", value)
    } else {
        fmt.Println("Key 'four' does not exist.")
    }
}

Output

Key 'one' exists with value: 1
Key 'four' does not exist.

Summary

In this tutorial, we learned How to Check if a Key Exists in a Map in Go language with well detailed examples.


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