Encapsulation prevents internal attribute values from being accessed directly from the outside and protects internal values by allowing access only through exposed methods (e.g. getter, setter). In other words, it hides the internal implementation and stores only valid values through data checking.

Let's write how to create getter and setter methods in Go using the Person struct below.

name, age are lowercase, so they cannot be accessed from the outside

type Person struct {
	name string
	age  int
}

Setter

• A Setter can be created as SetFoo()
  • To call the method from the outside, the first letter of the method is uppercase
• In a Setter, the receiver argument needs to be a Pointer receiver
  • This is because it must return the changed value after the method executes
• In a Setter, you can add data validation logic to check validity

func (p *Person) SetName(name string) error {
	if name == "" {
		return errors.New("invalid name")
	}
	p.name = name
	return nil
}

The SetName setter method takes name as an argument and stores the value in the name field of the Person struct. If name is empty, it returns an Error.

Getter

• A Getter is named with just the variable name, without prefixing it with Get
  • e.g. GetName() - X
  • e.g. Name() - O
  • Even if you write the code with GetName(), it works fine, but by Go convention, get is not used

func (p Person) Name() string {
	return p.name
}

A Getter returns only a value, so it doesn't need a pointer receiver argument. However, for consistency, it's good to declare it with a pointer receiver.

func (p *Person) Name() string {
   return p.name
}

The code written in this post can be found on github.

References

• https://www.socketloop.com/tutorials/golang-implement-getters-and-setters
• https://johngrib.github.io/wiki/golang-cheatsheet/
• https://golang.org/doc/effective_go.html?#Getters