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[MUSIC]

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Have you ever heard
the old boy scout rule,

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always leave the campground
cleaner than you found it?

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As software developers,
we want to adopt a similar rule.

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Every time we make a change to our code or
someone else's code, we want to try and

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clean it up or improve it in some way.

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We don't necessarily want to
make any big changes, but

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if we see an opportunity to let say user
valuable instead of a hard coded value,

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then we should make and test that change.

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The important thing to
emphasize here is that,

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we don't want to change the behavior
of the code, we're just looking for

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opportunities to make it a little
cleaner and more efficient, or

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maybe more maintainable for
someone else to work within the future.

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This process is known as refactoring.

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Let's see how we can do some
refactoring with our FunFact code.

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Right now, we have all of our code
in this FunFactsActivity class.

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And it works fine, but
what if we wanted to add a new activity

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that also randomly
selected one of our facts?

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We could copy all of these code and
add it to the new activity.

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But then we would have the same code doing
the same thing in two different places.

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Then if we change this code for
some reason,

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we have to remember to make the same
change to the code for the other activity.

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This violates a core principle
of software development,

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the don't repeat yourself principle.

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A better solution is to move the code
that is repeated to a reusable component.

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In this case, that could be a new object
that could be used in multiple activities.

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We learned before that activities are used
to control how things work on the screen.

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Our code does that, but

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it also controls how the effect
is generated behind the scenes.

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Let's make a new object that
separates out fact generation.

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Not only will it make our
code a little cleaner, but

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it will also prevent us from
repeating our ourselves in code.

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It's another good programming practice to
give each class a single responsibility.

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So in that case,

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the FunFactsActivity class will handle
only how the screen looks and works.

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And the new object,
which we'll call factBook, will only

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handle things about the facts themselves,
like how they're stored and selected.

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This is another programming
principle known as the single

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responsibility principle.

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All right,
let's create our new factBook object.

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There are a couple ways we can do this.

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We can go to File, New, and
then pick Kotlin File or Class,

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or in the Project Pane we can
right-click on our package and

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select New Kotlin File or Class.

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I'll choose this option.

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Then for the name let's type FactBook.

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And since we're making the class, let's
change the kind to Class and then hit OK.

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And here's our new file.

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If we look over to the project pane,

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we can see that a new FactBook file
has been added to our package.

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And our package now has two classes in it.

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Also, I already fixed
it from a high version.

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But at the top of your class,
Android Studio may have added a comment.

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I'm not a huge fan of
the automatic comment, but

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luckily we can change our preference
to make it not happen in the future.

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Follow along if you'd like.

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I'm going to click on Android Studio and
then open the preferences window.

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Then I'll expand Editor and
select File and Code Templates.

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And over on the Includes tab,
I'll select File Header and

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then delete everything in
the window on the right.

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Remember, mines empty cuz I've
already done this, then click OK.

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You'll still need to delete any
remaining comments by hand though.

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This class will be the blueprint for
our FactBook object.

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Remember, that an object has two
main components, Properties,

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which are characteristics of the object

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and Methods,
which are actions the object can take.

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This object only needs to do one thing,
get a random fact.

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Let's define a method for it.

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We'll call it getFact and

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it will return a string,
which will be the randomly chosen fact.

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Inside the class, type fun getFact
with open and closing parenthesis.

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Then let's make it return a string,
colon string, and add the brackets.

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Now we just need to make this
method return a random fact.

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Let's cut and paste some code from our
activity class into our getFact method,

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this is the refactoring part.

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Over in FunFactsActivity,
select everything in the OnClickListener

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except for the last two lines where
we're actually setting the text.

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Then let's cut the text with command or
Ctrl+X, and leave this error for

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now and go back to our FactBook class,
and paste in the code.

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We didn't copy over any of our imports, so

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hit OK to let Android Studio
automatically create the ones we need.

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GetFact now gets a random element
from the facts array, but

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we still need to return
which fact was selected.

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So instead of setting up a fact
variable with a random fact,

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let's just return the fact variable.

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Nice, we've just made
a new FactBook class and

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given it a method which
will return a random fact.

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Let's take a short break and

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then we'll see how we can use your
new method in FunFactsActivity.