Experiments with GoLang Custom Types

main.go

package main

// Experiments with GoLang Custom Types
// Playground link: https://play.golang.org/p/rHu1CBj0GvE

import "fmt"

// We can create our own types based on the concrete types.
// But Go will not consider our type "MyString" as the same type as the concrete
// type "string"
type MyString string

func CustomStringType_Experiment() {
	s := "hi"
	fmt.Println(s) // "hi"

	m := MyString("there")
	fmt.Println(m) // "there"

	// convert custom type back to concrete type
	ms := string(m)
	fmt.Println(ms) // "there"

	// if m == ms { // compiler error: mismatching types MyString, string
	// 	fmt.Println("m == ms")
	// }

	if string(m) == ms { // ok
		fmt.Println("string(m) == ms")
	}
}

// We can add methods to our custom types
type Strings []string

func (s *Strings) PrintValues() {
	for _, str := range ([]string)(*s) { // but we have to type convert before use
		fmt.Print(str, " ")
	}
	fmt.Println()
}

func AddFunctionToCustomType_Experiment() {
	ss := Strings{"a", "b", "c"}
	ss.PrintValues() // a b c
}

// Why would you want to do this?
// To satisfy an interface without using a struct.

type FunkyStringer []int

// satisfy fmt.Stringer interface
func (f FunkyStringer) String() string {
	var str string
	for _, val := range ([]int)(f) {
		str = fmt.Sprintf("%s- %d\n", str, val)
	}
	return str
}

func RunFunkyStringer_Experiment() {
	fs := FunkyStringer{3, 5, 7}
	fmt.Print(fs)
	// Output:
	// - 3
	// - 5
	// - 7

	fmt.Println(([]int)(fs)) // [3 5 7] (standard go value format)
}

func main() {
	CustomStringType_Experiment()
	AddFunctionToCustomType_Experiment()
	RunFunkyStringer_Experiment()
}