I'm trying to figure out how can I return a value from a function in a file of a package name to another package.
for example let's assume you have
package main
func main(){
x := 5
a := res.Test(x)
}
package res
func Test(x int) (y int){
y := x*2
return y
}
If I compile it I would get an error: res.Test used as value. Where am I doing wrong, how can I return y to the main/ and other package?
thx
At its most basic, a Go packages must be in their own file directory. res goes into ~/go/src/res/.
// ~/go/src/res/res.go
package res
func Test(x int) (y int){
// Note that y is already declared.
y = x*2
return y
}
Then your main.go can import this package.
package main
import(
"res"
"fmt"
);
func main(){
x := 5
a := res.Test(x)
fmt.Println(a)
}
See also
Here's a little further debugging for your specific error.
Note that the res code you posted should not compile. You should get an error like ./res.go:4:7: no new variables on left side of :=.
res.Test used as value indicates that res.Test does not return a value, but you tried to use it as one anyway. Your res.Test does have a return value.
Futhermore, your main.go is not importing res. You should have gotten an error like undefined: res but you didn't.
This indicates there's another res package floating around somewhere with a Test function with no return value.
