Go - 如何检查类型是否相等？

Question

Say I have the following code:

var x interface{}
y := 4
x = y
fmt.Println(reflect.TypeOf(x))

This will print int as the type. My question is how can I test for the type? I know there is the type switch which does this, so I could do:

switch x.(type) {
case int:
    fmt.Println("This is an int")
}

But if I only want to check for just one specific type the switch seems like the wrong tool. Is there a more direct method of doing this like

reflect.TypeOf(x) == int

or is the type switch the way to go?

Answer 1

Type assertions return two values .. the first is the converted value, the second is a bool indicating if the type assertion worked properly.

So you could do this:

_, ok := x.(int)

if ok {
    fmt.Println("Its an int")
} else {
    fmt.Println("Its NOT an int")
}

..or, shorthand:

if _, ok := x.(int); ok {
    fmt.Println("Its an int")
}

See it in the playground

Answer 2

I just figured out another way of doing this based on this :

if _, ok := x.(int); ok {
    fmt.Println("This is an int")
}

Answer 3

In Effective Go you can find a really simple example of what you're trying to achieve.

var t interface{}
t = functionOfSomeType()

switch t := t.(type) {
default:
    fmt.Printf("unexpected type %T", t)       // %T prints whatever type t has
case bool:
    fmt.Printf("boolean %t\n", t)             // t has type bool
case int:
    fmt.Printf("integer %d\n", t)             // t has type int
case *bool:
    fmt.Printf("pointer to boolean %t\n", *t) // t has type *bool
case *int:
    fmt.Printf("pointer to integer %d\n", *t) // t has type *int
}

If you have a single type that you have to check, use a simple if , otherwise use a switch for better readability.