While doing the final exercise of the Tour of Go, I decided I needed a queue of (string
, int
) pairs. That's easy enough:
type job struct {
url string
depth int
}
queue := make(chan job)
queue <- job{url, depth}
But this got me thinking: are there built-in pair/tuple data types in Go? There is support for returning multiple values from a function, but AFAICT, the multiple value tuples produced are not first-class citizens in Go's type system. Is that the case?
As for the "what have you tried" part, the obvious syntax (from a Python programmer's POV)
queue := make(chan (string, int))
didn't work.
You can do this. It looks more wordy than a tuple, but it's a big improvement because you get type checking.
Edit: Replaced snippet with complete working example, following Nick's suggestion. Playground link: http://play.golang.org/p/RNx_otTFpk
package main
import "fmt"
func main() {
queue := make(chan struct {string; int})
go sendPair(queue)
pair := <-queue
fmt.Println(pair.string, pair.int)
}
func sendPair(queue chan struct {string; int}) {
queue <- struct {string; int}{"http:...", 3}
}
Anonymous structs and fields are fine for quick and dirty solutions like this. For all but the simplest cases though, you'd do better to define a named struct just like you did.
You could do something like this if you wanted
package main
import "fmt"
type Pair struct {
a, b interface{}
}
func main() {
p1 := Pair{"finished", 42}
p2 := Pair{6.1, "hello"}
fmt.Println("p1=", p1, "p2=", p2)
fmt.Println("p1.b", p1.b)
// But to use the values you'll need a type assertion
s := p1.a.(string) + " now"
fmt.Println("p1.a", s)
}
However I think what you have already is perfectly idiomatic and the struct describes your data perfectly which is a big advantage over using plain tuples.
Source: Stackoverflow.com