Golang Interfaces
A Quick Lesson on Interfaces
While Go’s concurrency model (which we cover in Chapter 10) gets all of the publicity, the real star of Go’s design is its implicit interfaces, the only abstract type in Go. Let’s see what makes them so great.
We’ll start by taking a quick look at how to declare interfaces. At their core, interfaces are simple. Like other user-defined types, you use the type keyword.
Here’s the definition of the Stringer interface in the fmt package:
type Stringer interface { String() string }
In an interface declaration, an interface literal appears after the name of the interface type. It lists the methods that must be implemented by a concrete type to meet the interface. The methods defined by an interface are called the method set of the interface.
Like other types, interfaces can be declared in any block.
Interfaces are usually named with “er” endings. We’ve already seen fmt.Stringer, but there are many more, including io.Reader, io.Closer, io.ReadCloser, json.Marshaler, and http.Handler.