Function main

chapter10/listing05/listing05.go:48–81

=============================================================================

()

// =============================================================================

func main() {

	// Declare variables of the MoveLocker and Mover interfaces set to their
	// zero value.
	var ml MoveLocker
	var m Mover

	// Create a value of type bike and assign the value to the MoveLocker
	// interface value.
	ml = bike{}

	// An interface value of type MoveLocker can be implicitly converted into
	// a value of type Mover. They both declare a method named move.
	m = ml

	// prog.go:65: cannot use m (type Mover) as type MoveLocker in assignment:
	//	   Mover does not implement MoveLocker (missing Lock method)
	ml = m

	// Interface type Mover does not declare methods named lock and unlock.
	// Therefore, the compiler can't perform an implicit conversion to assign
	// a value of interface type Mover to an interface value of type MoveLocker.
	// It is irrelevant that the concrete type value of type bike that is stored
	// inside of the Mover interface value implements the MoveLocker interface.

	// We can perform a type assertion at runtime to support the assignment.

	// Perform a type assertion against the Mover interface value to access
	// a COPY of the concrete type value of type bike that was stored inside
	// of it. Then assign the COPY of the concrete type to the MoveLocker
	// interface.
	b := m.(bike)
	ml = b
}