How to check if an object has a particular method?

Question

In Go, how do you check if an object responds to a method?

For example, in Objective-C this can be achieved by doing:

if ([obj respondsToSelector:@selector(methodName:)]) { // if method exists
  [obj methodName:42]; // call the method
}

Answer 1

A simple option is to declare an interface with just the method you want to check for and then do a type assert against your type like;

 i, ok := myInstance.(InterfaceImplementingThatOneMethodIcareAbout)
 // inline iface delcataration example
 i, ok = myInstance.(interface{F()})

You likely want to use the reflect package if you plan to do anything too crazy with your type; http://golang.org/pkg/reflect

st := reflect.TypeOf(myInstance)
m, ok := st.MethodByName("F")
if !ok {
    // method doesn't exist
}
// do something like invoke m

Answer 2

If obj is an interface{} you can use Go type assertions:

if correctobj, ok := obj.(interface{methodName()}); ok { 
  correctobj.methodName() 
}