Golang-具有多种输入类型的功能

Question

I'm brand new to go and can't figure out how to do something pretty basic. Let's say that I have the following two structs:

type FooStructOld struct {
    foo1, foo2, foo3 int
}

type FooStructNew struct {
    foo1, foo2 int
}

I then want to have a function that updates the input. For example for a single type:

func updateval(arg *FooStructOld) {
    arg.foo1 = 1
}

This works as expected. However I would like the function updateval to take either FooStructOld or FooStructNew as an input. I know that I should be using an interface type but I can't quite get it to work. For example, when I try the following:

I get this error:

arg.foo1 undefined (type interface {} is interface with no methods)
cannot assign interface {} to a (type *FooStructOld) in multiple assignment: need type assertion

Does anyone know a solution for this?

Answer 1

You can either use a type assertion to extract the value from an interface{}

func updateval(arg interface{}) {
    switch arg := arg.(type) {
    case *FooStructOld:
        arg.foo1 = 1
    case *FooStructNew:
        arg.foo1 = 1
    }
}

Or you could implement an interface that does the update

type FooUpdater interface {
    UpdateFoo()
}

type FooStructOld struct {
    foo1, foo2, foo3 int
}

func (f *FooStructOld) UpdateFoo() {
    f.foo1 = 1
}

type FooStructNew struct {
    foo1, foo2 int
}

func (f *FooStructNew) UpdateFoo() {
    f.foo1 = 1
}

func updateval(arg FooUpdater) {
    arg.UpdateFoo()
}