In go there are functions which return two values or more values, commonly one is an error. Suppose that I want to store the first return value into an already initialized variable, but I would like to initialize the variable to contain the error inline. Is there a way to do this?
For example, say I had this code
var a int
//This code doesn't compile because err doesn't exist
a, err = SomeFuncWithTwoReturnValues()
//This code doesn't compile either
a, err := SomeFuncWithTwoReturnValues()
I know you could do this, but I was hoping there was a way to do it all inline
var a int
var err error
a, err = SomeFuncWithTwoReturnValues()
or
a, err := SomeFuncWithTwoReturnValues()
EDIT: The code above actually compiles, so I looked back at my code to drill down more and have created a quick sample that actually replicates the problem (not just in my mind...).
package main
func myfunc() (int, int) {
return 1, 1
}
func main() {
a := make([]int, 1)
a[0], b := myfunc()
a[0] = b
}
Compiler says main.go|9| non-name a[0] on left side of :=. If I make it = instead of := though then b is never created. I get the feeling that there is not shorthand way to do it though.
As you've mentioned in the comments, you'll need to use the = operator in order to assign to a variable you've already declared. The := operator is used to simultaneously declare and assign a variable. The two are the same:
var x int
x = 5
//is the same as
x := 5
This solution will at least compile:
package main
func myfunc() (int, int) {
return 1, 1
}
func main() {
var b int
a := make([]int, 1)
a[0], b = myfunc()
a[0] = b
}
To answer your question, I don't think there is a way to simultaneously use an undeclared and a declared variable when returning multiple values. That would be trying to use two different operators simultaneously.
Edit: just saw your example from the code that compiles, so it appears you're already familiar with go's assignment operators. I'll leave the example up anyway.