Golang中没有用于返回值的方法的“返回”

Question

I'm looking to the video tutorial of Go. I see there a type declaration and method that have to return a pointer of that type.

type testType struct {
    value int
}

func (h *testType) testFunction(w http.ResponseWriter, r *http.Request) {
    // we have empty body
}

As you see, function body is empty, there is no return statement.

• Why does it compile? I did not know that missing 'return' directives are permitted for methods that have to return some value. Could you tell me when they are not mandatory?
• What value will be returned in this case? Always nil?

Answer 1

That is not the return type of the function, it's a method and that is called the receiver type.

See Spec: Function declarations and Spec: Method declarations.

The return type is at the end of the function Signature, for example:

func testFunction(w http.ResponseWriter, r *http.Request) *testType {
    return nil
}

This is a function, having a return type of *testType.

This:

func (h *testType) testFunction(w http.ResponseWriter, r *http.Request) {
    // we have empty body
}

Is a method with receiver type *testType, and no return types.