Assign variable inside condition

Getting Help
1

I’d like to write this:

length := 10
if len(os.Args) == 2 {
       length, err = strconv.Atoi(os.Args[1])
		if err != nil {
			log.Fatal(err)
		}
	}

but I’m forced to write this:

length := 10
if len(os.Args) == 2 {
        l, err := strconv.Atoi(os.Args[1])
	if err != nil {
			log.Fatal(err)
	}
	length = l
}

Am I missing something?

2

Whats the problem with the first? The observable effect of both snippets should be the same

3

See here: https://play.golang.org/p/mo-cEC4uIhA
It won’t compile because I need to assign “err” for the first time

4

Well, I can also do this:

	length := 10
	var err error
	if len(os.Args) == 2 {
		length, err = strconv.Atoi(os.Args[1])
		if err != nil {
			log.Fatal(err)
		}
	}
5

I assumed you didn’t copy that part. Sadly I have an err to spare in about every other function when I have to write go and reuse it.

6

Change this:

length, err = strconv.Atoi(os.Args[1])

to this:

length, err := strconv.Atoi(os.Args[1])

As you’ve already created the length variable, but are creating the err variable right there in that line. Therefore, you need to add a “:” to declare the variable as well.

7

No, this will shadow length by declaring it in the inner scope as in this example: https://play.golang.org/p/2vdMbSjgrLW

1 Like
8

As @iegomez said, it introduces a subtle bug (well, in my snippet it won’t compile, but that’s only luck).
I think Assign variable inside condition is the cleanest solution, though I don’t quite like it.

9

Ah, whoops, you’re both right. Guess you’ll have to use that solution and declare the error beforehand.

10

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