CODEWITHSUNDEEP
goconstants
doubt
doubt

Reputation: 315

Use a literal value to refer to constant in Golang

I have defined a constant with a type. I want to use the value of a variable to refer to the constant. (Please refer to the code below). One way would be to define a map of Key to the required Value. Is there another approach to do this ?


import (
    "fmt"
    "reflect"
)

type Code int

const (
    MY_CONST_KEY Code = 123
)

func main() {
    x := "MY_CONST_KEY"
    //Fetch Value of x as 123
}

Upvotes: 1

Views: 2209

Answers (3)

Volker
Volker

Reputation: 42433

One way would be to define a map of Key to the required Value.

Yes, do that.

Is there another approach to do this ?

No.

Upvotes: -1

Nilabja Bhattacharya
Nilabja Bhattacharya

Reputation: 51

Instead of assigning x to a string, "MY_CONST_KEY", you can do x := MY_CONST_KEY

package main

import (
    "fmt"
)

type Code int

const (
    MY_CONST_KEY Code = 123
)

func main() {
    x := MY_CONST_KEY
    fmt.Println(x) // This fetch the value of x as 123
}

Upvotes: 0

Bracken
Bracken

Reputation: 1168

There is no way to do what you are asking. You cannot pass constants to the reflect package without instead passing their literal value.

As you correctly mentioned, you can use a map:

package main

import "fmt"

type Code int

var codes = map[string]Code{
    "MY_CONST_KEY":      123,
    "ANOTHER_CONST_KEY": 456,
}

func main() {
    x := codes["MY_CONST_KEY"]
    fmt.Println(x)
}

If you make sure the map is not exported (lower case c in codes), then it will only be available inside your package, so consumers of your package cannot modify the map at runtime.

Upvotes: 4

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