How to Set a Default Value for a Key in a Map in Go - Step by Step Examples

How to Set a Default Value for a Key in a Map in Go ?

Answer

To set a default value for a key in a map in Go, you can check if the key exists and if not, assign the default value using the subscript operator.

✐ Examples

1 Setting a Default Value Using an if Statement

We can set a default value for a key in a map in Go by checking if the key exists and if not, assigning the default value using the subscript operator.

For example,

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.
We use an if statement to check if the key exists in the map. If the key does not exist, we assign the default value using the subscript operator.
We print the updated map to the console using a for range loop and 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,
    }

    // Set a default value using an if statement
    if _, exists := myMap["four"]; !exists {
        myMap["four"] = 4
    }

    // Print the updated map
    for key, value := range myMap {
        fmt.Printf("%s: %d\n", key, value)
    }
}

Output

one: 1
two: 2
three: 3
four: 4

2 Setting a Default Value Using a Function

We can set a default value for a key in a map in Go by using a helper function that checks if the key exists and if not, assigns the default value.

For example,

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.
We define a helper function named setDefault that takes a map, a key, and a default value as arguments. The function checks if the key exists in the map and if not, assigns the default value using the subscript operator.
We call the setDefault function to set the default value for the key.
We print the updated map to the console using a for range loop and the fmt.Printf function.

Go Program

package main

import "fmt"

// Helper function to set a default value
func setDefault(m map[string]int, key string, defaultValue int) {
    if _, exists := m[key]; !exists {
        m[key] = defaultValue
    }
}

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

    // Set a default value using the helper function
    setDefault(myMap, "four", 4)

    // Print the updated map
    for key, value := range myMap {
        fmt.Printf("%s: %d\n", key, value)
    }
}

Output

one: 1
two: 2
three: 3
four: 4

3 Setting Multiple Default Values Using a Function

We can set multiple default values for keys in a map in Go by using a helper function that checks if the keys exist and if not, assigns the default values.

For example,

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.
We define a helper function named setDefault that takes a map, a key, and a default value as arguments. The function checks if the key exists in the map and if not, assigns the default value using the subscript operator.
We call the setDefault function to set multiple default values for the keys.
We print the updated map to the console using a for range loop and the fmt.Printf function.

Go Program

package main

import "fmt"

// Helper function to set default values
func setDefault(m map[string]int, key string, defaultValue int) {
    if _, exists := m[key]; !exists {
        m[key] = defaultValue
    }
}

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

    // Set multiple default values using the helper function
    setDefault(myMap, "four", 4)
    setDefault(myMap, "five", 5)

    // Print the updated map
    for key, value := range myMap {
        fmt.Printf("%s: %d\n", key, value)
    }
}

Output

one: 1
two: 2
three: 3
four: 4
five: 5

Summary

In this tutorial, we learned How to Set a Default Value for a Key in a Map in Go language with well detailed examples.

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How to Set a Default Value for a Key in a Map in Go - Step by Step Examples