Converting a custom type to string in Go

Question

In this bizarre example, someone has created a new type which is really just a string:

type CustomType string

const (
        Foobar CustomType = \"somestr         


        

Answer 1

Better to define a String function for the Customtype - it can make your life easier over time - you have better control over things as and if the structure evolves. If you really need SomeFunction then let it return Foobar.String()

   package main

    import (
        "fmt"
    )

    type CustomType string

    const (
        Foobar CustomType = "somestring"
    )

    func main() {
        fmt.Println("Hello, playground", Foobar)
        fmt.Printf("%s", Foobar)
        fmt.Println("\n\n")
        fmt.Println(SomeFunction())
    }

    func (c CustomType) String() string {
        fmt.Println("Executing String() for CustomType!")
        return string(c)
    }

    func SomeFunction() string {
        return Foobar.String()
    }

https://play.golang.org/p/jMKMcQjQj3

Answer 2

Convert the value to a string:

func SomeFunction() string {
        return string(Foobar)
}

Answer 3

For every type T, there is a corresponding conversion operation T(x) that converts the value x to type T. A conversion from one type to another is allowed if both have the same underlying type, or if both are unnamed pointer types that point to variables of the same underlying type; these conversions change the type but not the representation of the value. If x is assignable to T, a conversion is permitted but is usually redundant. - Taken from The Go Programming Language - by Alan A. A. Donovan

As per your example here are some of the different examples which will return the value.

package main

import "fmt"

type CustomType string

const (
    Foobar CustomType = "somestring"
)

func SomeFunction() CustomType {
    return Foobar
}
func SomeOtherFunction() string {
    return string(Foobar)
}
func SomeOtherFunction2() CustomType {
    return CustomType("somestring") // Here value is a static string.
}
func main() {
    fmt.Println(SomeFunction())
    fmt.Println(SomeOtherFunction())
    fmt.Println(SomeOtherFunction2())
}

It will output:

somestring
somestring
somestring

The Go Playground link

Answer 4

You can convert like this:

var i int = 42 var f float64 = float64(i)

check here

you can return like this:

return string(Foobar)

Answer 5

answering this for anyone who comes here searching. You can convert the type to string on return using fmt.Sprintf

click here to see it in action

func SomeFunction() string {
    return fmt.Sprintf("%v", Foobar)
}