Working with methods that receive protocols as arguments

Now, we will create additional instances of the previous classes and call methods that specified their required arguments with protocol names instead of class names. We will understand what happens under the hood when we use protocols as types.

In the following code, the first two lines of code create two instances of the AngryDog class named brian and merlin. Then, the code calls the two versions of the drawSpeechBalloon method for brian. The second call to this method passes merlin as the ComicCharacter argument because merlin is an instance of AngryDog, which is a class that implements the ComicCharacter protocol:

var brian = AngryDog(nickName: "Brian")
var merlin = AngryDog(nickName: "Merlin")
brian.drawSpeechBalloon("Hello, my name is \(brian.nickName)")
brian.drawSpeechBalloon(merlin, message: "How do you do?")
merlin.drawThoughtBalloon("Who are you? I think.")

Tip

Bear in mind that when we work with protocols, we use them to specify...