Embedded Interface and Type Assertions

Interface embedding interface(s)

An interface can contain the name of one (or more) interface(s), which is equivalent to explicitly enumerating the methods of the embedded interface in the containing interface. For example, the interface File contains all the methods of ReadWrite and Lock, in addition to a Close() method:

type ReadWrite interface {
  Read(b Buffer) bool
  Write(b Buffer) bool
}

type Lock interface {
  Lock()
  Unlock()
}

type File interface {
  ReadWrite
  Lock
  Close()
}

Detecting and converting the type of an interface variable

An interface type variable varI can contain a value of any type; we must have a means to detect this dynamic type, which is the actual type of the value stored in the variable at run time. The dynamic type may vary during execution but is always ...