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Methods
6:58Let's create our first method, a getter.
Okay so we've fixed our problem with
restricting changes to our character name,
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but it's a little too restrictive.
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It can't even be accessed from
outside the class itself.
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We want to allow consumers of our objects
to still be able to see the value,
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even if they can't change it.
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So how do we let them get the value then,
you ask?
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Great question.
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Well the answer is we build
a method that exposes a value.
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You've used methods before but for
instance on the console object use
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the print F method or on strings
we use the two lower case method.
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Now remember what I said that developers
modeling the real world objects focus on
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two main characteristics
which are state and behavior.
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Well fields usually are used
to express that state and
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its methods help us to
express that behavior.
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So, therefore you can kind of think of
fields as characteristics about your
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object and methods as the verbs or
actions that your object can perform.
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So, just like how you've use methods on
objects before, like string contains or
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integer percent, it's time that
we learn how to write our own.
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Okay, so let's do this.
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Let's add a method to our
object that behaves like this.
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When the method is used or
called it will respond with or
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return to the calling code.
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The value of the private
field character name.
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Now defining a method is pretty similar
More to the way that we define a field.
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They also have access modifiers.
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So let's come here.
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So when I come in here and
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say we definitely we want
this to be public right.
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We want this to be accessible,
that's the point of what we're doing.
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So we'll start with public and now,
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we need to define what type of data
will be returned from this method,
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meaning when I call this method, what
type of answer will I get back from it.
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For instance, let's look at one.
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So if we look at the method
string.contains,
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remember you use that to find
out if something's in there.
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So that is definitely a public method,
right.
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We are using that, and
it returns a Boolean okay.
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So we said that our method was going
to be returning a string, right?
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It's the character name.
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It's a string so so we say, public string.
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And next is the method name so
we're going to get the character names so
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getCharacterName.
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Now, here's the part that makes it
different than the field definition.
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Look, it looks pretty similar, right?
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What we're going to do is we're
going to open parentheses
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stating that this is indeed a method and
it's expected to be called.
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So, here is where you
would define parameters,
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that's if your method needs it.
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So, if we come back to the string contains
method, so it's a public Boolean that
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contains is the name of the method and
again it opens up its parentheses.
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And it needs to know, a parameter we pass
in the string containing words right?
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Remember we did that.
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So back at our example of contains it
needs you to specify what you're looking
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for the contains method
takes a string argument.
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So it's a string of the matching
text that you're looking for, right?
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It specifies that parameter list.
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We'll go over these in a bit but currently
our method doesn't need any parameters.
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So we'll just go ahead and close it and
then we'll start our methods body.
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So it's opening up a new scope and I'll
write right away to put the closing brace.
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So you see all of the editor lines up
the braces, it's really nice this way.
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So now if I come here, I know this is the
class scope and here is this method scope.
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It's a nice way to make sure that
everything's lining up in one class.
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Okay, back to our method.
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In this scope here in this code
block we can write whatever we want.
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In here we can write whatever code the
method should perform when it's called.
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Finally, what should happen is,
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it should return a value of its
expected type, which is string.
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So it's going to use the keyword return.
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And we're going to return
the characterName, right?
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And the character name is
a string characterName.
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So here's the characterName.
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It's going to return this and because it's
in the scope right it's in this class
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scope it has access to this
even though it's private.
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The prefix of get here is part
of a very common pattern.
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It's called a getter, this pattern
of getter for a specific field
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is to name them with get followed by
the name of the field just like we did.
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GetCharacterName so
you can see it's get and
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then character a name and it's getting
this private field character name here.
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So methods that are used to change
the state of these objects or
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set a field value
are prefixed with set and
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those are called of course setters so
together these getters and
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setters are often referred to as
properties in other languages.
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They'll become very common practice for
you in your job adventures.
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Okay, so
now let's flip back to the example.
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I'm gonna go ahead and before we do that,
I'm gonna get rid of this comment here.
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I wanna save this file, and let's
flip back to example and take a look.
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So we know that the code in here doesn't
compile remember it wasn't compiling,
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so let's go ahead.
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Let's get rid of this Darth Vader cuz
we're not gonna change that anymore,
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it's private.
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But now, instead of accessing the private
field character name, let's try to access
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the public method, getCharacterName,
and we're going to call that method.
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So there's some parens I'll put
this down in a new line in here.
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This is highlighting, this is this, okay.
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So we're going to call the method,
getCharacterName and
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that's going to return the method.
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So let's go ahead and
let's compile it and run it.
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I forgot to save it important note
there see the little red dot.
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So compile it and run it.
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Boom we got it, it's back.
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So again the method was called and
our code inside of that method.
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This method body here was run and we
returned the private field characterName.
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And that's definitely more like how
things work in real life, right?
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People can't just go changing
the character on these pez dispensers and
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now we are clearly communicating that
reality because we haven't added a setter
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we've only add it together so
nobody can set that.
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Now, one thing you're probably wondering
is well, we can't change it at all,
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right, it's always going to be Yoda.
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That's a good point.
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Let's tackle that next awesome
job modeling the character.
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Now it can't be changed only retrieved.
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This is a very common pattern
used to express how you'd
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like people to interact with your object.
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We'll run through it a couple more
times in the course just to make sure
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that it's sinking it.
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So we left another problem in there,
didn't we?
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Every single Pez dispenser that we
create is gonna be a Yoda character.
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That's certainly gonna bum out some kids
who want a Teenage Mutant Ninja Turtle or
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an Elsa version, and for
sure sales are gonna plummet.
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Let's do a quick exercise to make sure
that we got this private keyword and
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getter method thing figured out, and
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then we'll fix this Yoda only
situation that we got ourselves into.
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