Go

Examples of how to create maps.

package main

import "fmt"

func main() {
	// A map is an unordered collection of key-value pairs.
	initials := make(map[string]string)
	initials["JD"] = "Jack Doleman"
	initials["PL"] = "Patrick Lock"
	initials["HS"] = "Harry Saker"

	fmt.Println(initials["HS"])

	// You can return two values when accessing an element.
	// The first value below returns zero value (empty string).
	// The second (bool) value is for whether the lookup was successful.
	name, ok := initials["BP"]
	fmt.Println(name, ok)

	// Here the lookup is successful
	name, ok = initials["PL"]
	fmt.Println(name, ok)

	// Print if it's successful.
	// N.B. A statement can procede conditionals.
	if name, ok = initials["JD"]; ok {
		fmt.Println(name, ok)
	}

	// You can also declare and initialise a new map a shorter way.
	numbers := map[int]string{
		1: "One",
		2: "Two",
		3: "Three",
		4: "Four",
		5: "Five",
	}
	fmt.Println(numbers)

	// You can also store further values with an inner map.
	people := map[int]map[string]string{
		1: map[string]string{
			"firstname":      "Jack",
			"middle initial": "A.",
			"surname":        "Doleman",
		},
		2: map[string]string{
			"firstname":      "Patrick",
			"middle initial": "C.",
			"surname":        "Lock",
		},
		3: map[string]string{
			"firstname":      "Harry",
			"middle initial": "V.",
			"surname":        "Saker",
		},
	}
	if person, ok := people[3]; ok {
		fmt.Println(person["firstname"], person["middle initial"], person["surname"])
	}
}