mutations.go

package main

import "fmt"

type Person struct {
	name string
}

func mutateWithRange(people []Person) {
	for _, person := range people {
		person.name = "Foobar"
	}
}

func mutateWithForLoop(people []Person) {
	for i := 0; i < len(people); i++ {
		people[i].name = "Foobar"
	}
}

func main() {
	a := Person{name: "Nick"}
	b := Person{name: "Michaela"}
	c := Person{name: "Simon"}

	people := []Person{a, b, c}
	people2 := []Person{a, b, c}

	// In a range, each member of a slice
	// gets copied (passed by value), so
	// mutations don't persist beyond block scope
	mutateWithRange(people)
	fmt.Println(people)
	// [{Nick} {Michaela} {Simon}]

	// With a `for` loop, each member of a slice
	// is accessed directly, so mutations persist
	mutateWithForLoop(people2)
	fmt.Println(people2)
	// [{Foobar} {Foobar} {Foobar}]
}