Idioms and language features

Naked returns

A naked return omits the return values when the function uses named return values. Name the return values in the signature, assign them in the body, then return with no arguments:

func nakedReturn() (a, b string) {
	a = "First string"      // named return vals
	b = "second string"
	return                  // naked return
}

Comma-ok

The comma-ok idiom uses a second boolean return value to distinguish a missing key or failed assertion from a zero value.

Maps

m := map[string]int{"a": 1}
v, ok := m["a"] // v = 1, ok = true
x, ok := m["b"] // x = 0 (zero value), ok = false

Type assertions

var i interface{} = "hello"
s, ok := i.(string) // s = "hello", ok = true
n, ok := i.(int)    // n = 0, ok = false

Channel receives

Channel receives use comma-ok to check whether a channel is closed:

• If the channel is open, you receive a value and ok is true.
• If the channel is closed, you receive the zero value for the type and ok is false.

ch := make(chan int)
close(ch)
v, ok := <-ch // v = 0, ok = false (channel closed)