如何获取类型的字符串表示形式？

Question

Let's say I have the following type defined:

type ID uuid.UUID

How would I get the type as string in a programmatic way so it's easy to refactor later other than maybe:

fmt.Sprintf("%T", ID{})

which I don't quite like because it instantiates it, also from an Interface.

Answer 1

You may use package reflect (the fmt package does that too under the hood). You may start from the pointer to the type, and use a typed nil pointer value without allocation, and you can navigate from its reflect.Type descriptor to the descriptor of the base type (or element type) of the pointer using Type.Elem().

Example:

t := reflect.TypeOf((*ID)(nil)).Elem()
name := t.Name()
fmt.Println(name)

Output (try it on the Go Playground):

ID

Note: be aware that Type.Name() may return an empty string (if the Type represents an unnamed type). If you're using a type declaration (with the type keyword), then you already named the type, so Type.Name() will return a non-empty type name. But using the above code for a variable of type *[]string for example will give you an empty string:

var s *[]string
t := reflect.TypeOf(s).Elem()
name := t.Name()
fmt.Printf("%q", name)

Output (try it on the Go Playground):

""

See related questions:

Golang reflect: Get Type representation from name?

Identify non builtin-types using reflect