How do you retrieve a list of method names from an interface in Go using reflection?

Getting a List of Method Names from an Interface

In Go, reflection allows for inspecting and manipulating the internal structure of a program at runtime. This includes the ability to access information about an interface type, such as its method names.

Consider the following interface:

<code class="go">type FooService interface {
    Foo1(x int) int
    Foo2(x string) string
}</code>

To obtain a list of the method names for this interface using reflection:

1. Obtain the reflect.Type for the interface type:

<code class="go">t := reflect.TypeOf((*FooService)(nil)).Elem()</code>

This line retrieves the reflect.Type for the concrete type that implements the FooService interface.

2. Retrieve the number of methods:

<code class="go">for i := 0; i < t.NumMethod(); i++ {</code>

The NumMethod() function returns the number of methods in the interface.

3. Get the method names:

<code class="go">s = append(s, t.Method(i).Name)</code>

The Method(i) function returns a reflect.Method object representing the method at index i. The Name field of this object contains the name of the method.

The resulting list s will contain the method names ["Foo1", "Foo2"].

Explanations:

• The (*FooService)(nil) syntax is used to create a pointer to an anonymous instance of the FooService interface. This is necessary to obtain the reflect.Type for the interface.
• The Elem() method returns the reflect.Type for the concrete type that implements the interface, instead of the interface type itself.
• The NumMethod() function returns the number of methods declared in the interface, even if the concrete type implements additional methods.

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