How to Iterate Over a Map in Go

1. Introduction

Iterating over maps in Go is a fundamental technique that allows you to access every key-value pair within a map. This is especially useful when you need to perform operations on map data or extract information. In this blog post, we'll demonstrate how to loop through a map in Go.

2. Program Steps

1. Create and populate a map with sample data.

2. Iterate over the map using a for range loop.

3. Print out each key-value pair from the map.

3. Code Program

A map is a data structure that stores data in key-value pairs. To iterate over a map, Go provides a range loop that returns both the key and the value for each entry in the map.

package main

import "fmt"

func main() {
	// Step 1: Create and populate a map
	phoneBook := map[string]string{
		"Alice": "555-1234",
		"Bob":   "555-5678",
		"Carol": "555-7890",
	}

	// Step 2: Iterate over the map
	fmt.Println("Phone Book Listings:")
	for name, number := range phoneBook {
		// Step 3: Print each key-value pair
		fmt.Printf("%s: %s\n", name, number)
	}
}

Output:

Phone Book Listings:
Alice: 555-1234
Bob: 555-5678
Carol: 555-7890

Explanation:

1. package main - The package declaration for the Go program.

2. import "fmt" - Includes the Format package, which provides I/O functionality.

3. phoneBook is declared and initialized with a map literal containing three key-value pairs, representing a simple phone book.

4. A for range loop iterates over phoneBook. On each iteration, name receives the key and number receives the corresponding value.

5. Inside the loop, fmt.Printf is used to print each name and their associated phone number to the console.

6. The output lists all the entries in the phoneBook map, confirming that the map was successfully iterated over and all key-value pairs were accessed.