[Go] Filter an Array in Go

Golang has no built-in function(s) to filter an array. This lesson will teach you two different ways to filter.

The first is to create a separate array and add the filtered elements to it. This works great, but doesn't use memory as efficiently as the second way.

The second way shows you how to filter by altering the original array in place without making another array to hold the filtered elements. But, it has a side-effect that I'll tell you about which may help you decide which approach you will use to filter your array.

package main

import (
	"fmt"
	"log"
)

func main() {
	champions, err := loadChampions()
	if err != nil {
		log.Fatalf("An error occurred loading/parsing champions, err=%v", err)
	}

	fmt.Printf("There are %d total champions: %v\n\n", len(champions), champions)

	brawlers := filter(champions, func(champ champion) bool {
		return champ.hasClass("Brawler") && champ.Cost >= 3
	})

	fmt.Printf("Found %d brawlers, %v\n\n", len(brawlers), brawlers)
	fmt.Printf("There are %d total champions: %v\n\n", len(champions), champions)
}

func filter(champs []champion, f filterFunc) []champion {
	var result []champion
	for _, champion := range champs {
		if f(champion) {
            result = append(result, champion)
		}
	}

	return append
}

type filterFunc func(champion) bool