在NewX函数上返回指针背后有充分的理由吗？ [重复]

Question

This question already has an answer here:

• Why should constructor of Go return address? 1 answer
• Pointers vs. values in parameters and return values 3 answers

Is there a good reason for returning pointers on the "constructor" of a struct? For example:

type MyType struct{}

func NewMyType() *MyType {
  var m *MyType
  return m
}

vs.

type MyType struct{}

func NewMyType() MyType {
  var m MyType
  return m
}

In most cases, the "constructors" accept some arguments and return a pointer to a type. Why not just return a value?

Thanks in advance.

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Answer 1

The return type typically depends on how the type is intended to be used. Here are some examples:

The time.Time and reflect.Value types are intended to be used as values. The methods on these types have a value receiver. The constructor functions for these types return a value.

The bufio.Reader type is passed around as a pointer. The type wouldn't work at all if bufio.Reader types are passed around as a value. The constructor functions return a pointer.

All this begs the question about using values vs. pointers. That issue is covered well in other answers here on the StackOverflow.