什么时候应该在Go中针对值（而不是指针）定义方法？

Question

Having defined

type MyInt int

I would like to define a method .ShowMe() that just prints the value. I can define this either using *MyInt:

func (this *MyInt) ShowMe() {
    fmt.Print(*this, "
")
}

Or using MyInt:

func (this MyInt) ShowMe() {
    fmt.Print(this, "
")
}

In what cases is it recommended to define methods on values, instead of on pointers?

Answer 1

There are two questions to ask yourself when making this decision:

1. Do I want to be able to modify the receiver's value?
2. Will copying the receiver's value be expensive?

If the answer to either of these questions is yes, then define the method on a pointer.

In your example, you don't need to modify the receiver's value and copying the receiver isn't expensive.

For deciding the answer to #2, my rule of thumb is: if the receiver is a struct with more than one field, pass by pointer. Otherwise pass by value.