是否可以更改存储在空接口中的结构的成员

Question

I have this:

type pair struct {
    a, b int
}

Then I define two variables:

x := pair{ 3, 4 }
var y interface{} = x

I realize that y doesn't store a reference of x but a copy of it via the following code:

x.b = 7
fmt.Println(x)
fmt.Println(y)
// got:
// {3 7}
// {3 4}

Also see: https://github.com/golang/go/blob/master/src/runtime/iface.go#L359

Is there any way to modify pair.y member of the copied struct in y?

Tried this: (fail)

// cannot assign to y.(pair).b
y.(pair).b = 7

Tried this: (also fail)

// panic: reflect: reflect.Value.SetInt using value obtained using unexported field
v := reflect.ValueOf(y).FieldByName("b")
v.SetInt(33)

Change "b" to "B": (also fail)

type pair {
    a, B int
}
// panic: reflect: reflect.Value.SetInt using unaddressable value
v := reflect.ValueOf(y).FieldByName("B")
v.SetInt(33)

---

Update:

I'm not going to change x.b using y. I want to change y's field b alone.

Thanks for your help, but this is not a simple question about values and references.

Answer 1

You need to know the pointer and address first.Use the pointer can change the value deeply.If you want y to have the same value as x, they need to point to the same address.