Go Language - Maps - Example

A map is an unordered collection of key/value pairs, where each key is unique. We can create a new map with a make statement or a map literal. The default zero value of a map is nil. The len function returns the size of a map. Go Range keyword is used in different kinds of data structures in order to iterate over elements.

Create a Map:

Create a Map called users that will store int keys and String values:

 /* Create a new map
     * Empty map of string-string pairs
     */
    users := make(map[int]string)   

Add Items:

Add a new key-value pair,

  //Add Items
    users[1] = "scott"
    users[2] = "june"
    users[3] = "april"
    users[4] = "carl"
    users[5] = "rick"
    users[6] = "daryl"

Update Value:

// Update value
    users[6] = "michonne"

Iterate over all keys and values:

 // Iterating over all keys and values
    for id, name := range users {
        fmt.Printf("id :%d name: %s\n", id, name)
    }

Access an Item:

 //Access an Item
    fmt.Println("\n", users[1], "\n")

Remove an Item:

//Remove an Item
    delete(users, 3)

Test if entry is present in the map or not:

// Test if entry is present in the map or not
    _, status := users[4]
    fmt.Println("\n", status, "\n")

Complete Code:

package main

import "fmt"

//Required imports

func main() {

    /* Create a new map
     * Empty map of string-string pairs
     */
    users := make(map[int]string)

    //Add Items
    users[1] = "scott"
    users[2] = "june"
    users[3] = "april"
    users[4] = "carl"
    users[5] = "rick"
    users[6] = "daryl"

    fmt.Println("\n")

    // Iterating over all keys and values
    for id, name := range users {
        fmt.Printf("id :%d name: %s\n", id, name)
    }

    // Update value
    users[6] = "michonne"

    fmt.Println("\n")

    // Iterating over all keys and values
    for id, name := range users {
        fmt.Printf("id :%d name: %s\n", id, name)
    }

    //Access an Item
    fmt.Println("\n", users[1], "\n")

    //Remove an Item
    delete(users, 3)

    // Iterating over all keys and values
    for id, name := range users {
        fmt.Printf("id :%d name: %s\n", id, name)
    }

    // Test if entry is present in the map or not
    _, status := users[4]
    fmt.Println("\n", status, "\n")
}

Output: