douhan8009
2017-03-23 10:30 阅读 326
已采纳

Golang中没有用于返回值的方法的“返回”

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?
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1条回答 默认 最新

  • 已采纳
    dousi1097 dousi1097 2017-03-23 10:32

    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.

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