How Can I Retrieve the `reflect.Kind` of an Interface Type Underlying a Primitive in Go?

Retrieve Reflect.Kind for Types Based on Primitives: A Detailed Explanation

Often, developers encounter the need to determine the reflect.Kind of a type that has an underlying implementation based on a primitive type, such as:

type ID interface {
    myid()
}

type id string

func (id) myid() {}

In the above example, the "id" type implements the "ID" interface using an underlying string primitive. The challenge lies in retrieving the reflect.Interface value instead of the default reflect.String kind.

Unveiling the Solution: Pointer to Interface

A common misconception is to pass a value of type "id" to reflect.TypeOf(). However, this results in an implicit repackaging of the value into an interface{} with the embedded string primitive.

The key to overcoming this hurdle is to leverage a pointer to the interface. By passing a pointer, the type descriptor wraps an interface{}, preventing repackaging. Subsequently, we can use Type.Elem() to retrieve the type descriptor of the pointed interface, which will accurately reflect the type's interface nature.

id := ID(id("test"))

t := reflect.TypeOf(&id).Elem()

fmt.Println(t.Kind()) // Output: interface

This approach effectively reveals the desired reflect.Interface kind for types rooted in primitives.

Additional Insights: Pointer to Interface Benefits

This technique not only solves the initial problem but also highlights the benefits of using pointers to interfaces. In certain cases, such as passing values to functions that expect a specific type (e.g., a String or Time), a pointer to interface can be advantageous for avoiding implicit conversions.

By following these guidelines, developers can accurately retrieve the reflect.Kind of types that stem from primitives, gaining a deeper understanding of Go's reflection capabilities.

The above is the detailed content of How Can I Retrieve the `reflect.Kind` of an Interface Type Underlying a Primitive in Go?. For more information, please follow other related articles on the PHP Chinese website!