Interface Implementation

Interfaces are implemented implicitly.

A type never declares that it implements a given interface. If an interface exists and a type has the proper methods defined, then the type automatically fulfills that interface.

A quick way of checking whether a struct implements an interface is to declare a function that takes an interface as an argument. If the function can take the struct as an argument, then the struct implements the interface.

Assignment

At Textio we have full-time employees and contract employees. We have been tasked with making a more general employee interface so that dealing with different employee types is simpler.

1

Run the code

You should see an error indicating the contractor type does not fulfill the employee interface.

2

Add the missing method to contractor

Add the missing getSalary method to the contractor type so that it fulfills the employee interface.

• Note: A contractor's salary is their hourly pay multiplied by how many hours they work per year.

Solution

main.go

package main

type employee interface {
	getName() string
	getSalary() int
}

type contractor struct {
	name         string
	hourlyPay    int
	hoursPerYear int
}

func (c contractor) getName() string {
	return c.name
}

func (c contractor) getSalary() int{
	return c.hourlyPay * c.hoursPerYear
}

type fullTime struct {
	name   string
	salary int
}

func (ft fullTime) getSalary() int {
	return ft.salary
}

func (ft fullTime) getName() string {
	return ft.name
}