Ensure a type implements an interface in Golang
go
package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
func main() {}package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
func main() {}To ensure that Rectangle type implements the Shape interface, we check it at compile time.
go
package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
var _ Shape = (*Rectangle)(nil)
func main() {}package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
var _ Shape = (*Rectangle)(nil)
func main() {}Compiling the code above gives us the following error:
cannot use (*Rectangle)(nil) (value of type *Rectangle) as type Shape in variable declaration:
*Rectangle does not implement Shape (missing Area method)cannot use (*Rectangle)(nil) (value of type *Rectangle) as type Shape in variable declaration:
*Rectangle does not implement Shape (missing Area method)Implementing the interface gets rid of the compile error
go
package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
func (r *Rectangle) Area() int {
return r.Width * r.Height
}
var _ Shape = (*Rectangle)(nil)
func main() {}package main
type Shape interface {
Area() int
}
type Rectangle struct {
Width int
Height int
}
func (r *Rectangle) Area() int {
return r.Width * r.Height
}
var _ Shape = (*Rectangle)(nil)
func main() {}