CODEWITHSUNDEEP
go
Soumendra
Soumendra

Reputation: 1624

undefined variable name while checking if-else conditions in go

I have written the following program while learning from a tutorial. This is about checking conditionals in go.
However, it is throwing error as undefined message. Please help.


// Check out various conditional operators

package main

import "fmt"

func condition(x int) string {
    if x > 5 {
        message := "x is greater than 5"
    } else if x == 5 {
        message := "x is equal to 5"
    } else {
        message := "x is less than 5"
    }
    return message  // error on this line
}

func main() {
    x := 10 - 5
    msg := condition(x)
    fmt.Println("%s", msg)
}

Output receiving is:

user$ go run conditionals.go 
# command-line-arguments
./conditionals.go:15:9: undefined: message

Upvotes: 0

Views: 545

Answers (2)

colm.anseo
colm.anseo

Reputation: 22027

message is scoped in each of the if/else branches. You want it scoped at the function level:

func condition(x int) string {
    var message string
    if x > 5 {
        message = "x is greater than 5"
    } else if x == 5 {
        message = "x is equal to 5"
    } else {
        message = "x is less than 5"
    }
    return message
}

Since you are returning this value, you can update the function signature to include the returned variable e.g.

func condition(x int) (m string) {

    if x > 5 {
        m = "x is greater than 5"
    }
    // ...

    return // implicitly returns m value
}

Upvotes: 2

jkr
jkr

Reputation: 19250

The problem is you define message within a scope (i.e., inside curly braces), and your return statement is outside of those brackets. A solution would be to define message in the same scope as your return statement, and then redefine message in each conditional clause.

package main

import "fmt"

func condition(x int) string {
    message := ""
    if x > 5 {
        message = "x is greater than 5"
    } else if x == 5 {
        message = "x is equal to 5"
    } else {
        message = "x is less than 5"
    }
    return message
}

func main() {
    x := 10 - 5
    msg := condition(x)
    fmt.Println(msg)
}

https://play.golang.org/p/z_8h0ISNKYO

Upvotes: 1

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