如何检查空片？

I am calling a function that returns an empty array if there are no values.

When I do this it doesn't work:

if r == [] {
    fmt.Println("No return value")            
}

The work around I'm using is:

var a [0]int
if r == a {
    fmt.Println("No return value")            
}

But declaring a variable just to check the return value doesn't seem right. What's the better way to do this?

len() returns the number of elements in a slice or array.

Assuming whatever() is the function you invoke, you can do something like:

r := whatever()
if len(r) > 0 {
  // do what you want
}

or if you don't need the items

if len(whatever()) > 0 {
  // do what you want
}

You can just use the len function.

if len(r) == 0 {
    fmt.Println("No return value")            
}

Although since you are using arrays, an array of type [0]int (an array of int with size 0) is different than [n]int (n array of int with size n) and are not compatible with each other.

If you have a function that returns arrays with different lengths, consider using slices, because function can only be declared with an array return type having a specific length (e.g. func f() [n]int, n is a constant) and that array will have n values in it (they'll be zeroed) even if the function never writes anything to that array.

You can use the inbuilt function provided by Golang

len()

It will helps you to easily find a slice is empty or not.

if len( yourFunction() ) == 0 {
    // It implies that your array is empty.
}