This lesson's interactive features are locked, please to keep using them

Multiple Interfaces

A type can implement any number of interfaces in Go. For example, the empty interface, interface{}, is always implemented by every type because it has no requirements.

Assignment

Complete the required methods so that the email type implements both the expense and formatter interfaces.

Complete the cost() method:

If the email is not "subscribed", then the cost is 5 cents for each character in the body.
If it is, then the cost is 2 cents per character.
Return the total cost of the entire email in cents.

Complete the format() method.

It should return a string in this format:

'CONTENT' | Subscribed

If the email is not subscribed, change the second part to "Not Subscribed":

'CONTENT' | Not Subscribed

The single quotes are included in the string, and CONTENT is the email's body. For example:

'Hello, World!' | Subscribed

You may want to import the fmt package and use Sprintf.