Go Interfaces

Internal

• The Type System

Overview

An interface is a type declaration that defines a method set. A method set is a list of methods a type must have in order to implement the interface. Interface type instances can be used as arguments to functions, an interface instance can be passed as argument to a function after declaring it as such in the function signature.

A type implements an interface implicitly, by doing nothing else but exposing all methods from the interface's method set. This is called duck typing.

• Interfaces are not types?
• Can only structs be interfaces, or there are other things that can be interfaces?

Declaration

The interface declaration is introduced by the type keyword, to indicated that this is a user-defined type, followed by the interface name and the keyword interface. Unlike in the struct's case, we don't define fields but a method set.

type MyInterface interface {
     functionName1() return_type
     functionName2() return_type
     ...
}