How to reference a variable in a String like is possible in tests in Golang?

Question

The following works in tests:

if actualKey != expectedKey {
    t.Fatalf("Failed. Actual: %q. Expected: %q", actualKey, expectedKey)
}

In the main code:

m["Keyword "+kw+" found on "+url] = 0

, but this fails:

m["Keyword %q found on %q", kw, url] = 0

As suggested by @JimB fmt.Sprintf could be used. The following works:

msg := fmt.Sprintf("Keyword %q found on %q", kw, url)
m[msg] = 0

Questions

Is it correct to call this approach variable referencing? If false, what is it called?
Is this the most concise way of implementing it?

Are you just looking for string formatting? [`fmt.Sprintf`](https://golang.org/pkg/fmt/#Sprintf)? — JimB, Jul 21 '16 at 13:06
@JimB Thank you. It works. I have updated the questions. Could you post an answer and answer the additional questions? — 030, Jul 21 '16 at 13:15
Possible duplicate: http://stackoverflow.com/questions/11123865/golang-format-a-string-without-printing. What is string formatting called? -- "Formatting"? (that's what the `f` on the end of `Fatalf`, `Printf`, `Sprintf` signifies). What do you mean the most concise way to implement it? Are you trying to write your own formatter? — JimB, Jul 21 '16 at 13:28
@JimB No. I do not want to reinvent the wheel. `msg := fmt.Sprintf("Keyword %q found on %q", kw, url)` — 030, Jul 21 '16 at 13:31
@JimB calling variables in a String is just called String Formatting? "hello" + var is called the same as fmt.Sprintf("hello %q", var)? — 030, Jul 21 '16 at 13:34
`"hello " + var` only works with 2 strings, hence it's simple concatenation. String formatting "formats" the variables in different ways depending on the verb being used., for example you used `%q`, which adds quotes around strings. That's not really the same as concatenating two strings. — JimB, Jul 21 '16 at 13:37
@JimB I agree with that. I was wondering whether there is a name for the latter. `String concatenation` vs. `?` — 030, Jul 21 '16 at 13:50

score 0 · Accepted Answer · answered Jul 21 '16 at 13:50

0

I think a better way to do it is by defining a struct type:

type Result struct {
    Keyword, URL string
}

and use it like this:

m := make(map[Result]int)
m[{"keyword1", "url1"}] = 0

answered Jul 21 '16 at 13:50

seriousdev

1 Answers1