Go: Assign multiple return value function to new and old variable

Question

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.

Answer 1

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.