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Code Generation
8:26Why not let your IDE write some code for you? It knows the best practices.
[MUSIC]
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>> So when we delivered our minimum viable
project, or MVP, for the karaoke project,
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there was another story that
didn't quite make the cut and
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it got left in the backlog.
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It was this.
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As a KJ I should know which
singer requested the song so
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that I can call them up to the stage.
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Well as it turns out, after some usage
most KJs are dying for that feature.
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What happens is this.
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They keep calling the song and no one
comes up because they either forgot or
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they are not paying attention.
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So let's see if we can add this
feature request to our app real quick.
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>> A song request is
definitely a model right?
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So let's navigate over there.
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And, in the model package we'll right
click, and say New, Java Class.
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And let's call it SongRequest.
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Cool.
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This is some default setting.
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I'm gonna get rid of it.
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Okay.
So, let's see.
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We know we want a couple of things.
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Right?
We wanna have a private
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String let's call it mSingerName.
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We want a singer and let's go ahead and
pop the song in there so private
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Song and mSong.
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Now remember, it was in the same package
as a song so we didn't need to import it.
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So I want to explore something
now called code generation.
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So we wanna have a constructor, right?
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The good new is is that
it can create one for us.
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Because remember, what we want it to do is
we want it to pass in the singer name and
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the song when you get created.
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Let's go ahead and we'll go up to Code.
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Then we'll choose generate.
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Yeah, we're gonna generate a constructor.
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We want it to do both of those, right?
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We want it to do both those things.
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Okay.
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Whoops.
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Okay, so almost.
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The problem is that the parameters here
are following our naming structure,
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where we put the member variables
in at the front, right.
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Remember, that's just a coding
style that we're doing and
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each project that you work on
might adhere to different styles.
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Well the cool thing is that
your editor knows that,
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we just need to tell it our style.
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So I am going to go ahead and I am going
to Cmd+Z this, get rid of that and
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let's go under File,
Other Settings, Default Settings.
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And if we go under Editor,
Code Style, Java and Code Generation.
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Here's the naming stuff.
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Whenever we have a field,
we're gonna prefix it with an m.
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Okay, that's really all you have to do.
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Say Apply.
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Let's go take a look and
see if that worked.
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So now if we come over here,
the generating code thing,
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I don't know if you saw it, it was Cmd+N.
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So I'm gonna generate a constructor and
we're gonna use both of those.
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Blam, there it is.
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So, setting that up.
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Song got moved down there.
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Let's move him back up to where he was.
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There we go.
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Okay.
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So now the boring part of
adding getters and setters.
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Did you see that in the list?
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We can do that too.
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We don't need to do that anymore.
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Let's choose getter and setter and
let's make them for both.
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You'll note here that there's templates.
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We're gonna leave them.
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That's fine.
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Look at that.
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We didn't have to write all that code.
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What else is in that generate thing?
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Let's see.
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toString, that's something handy.
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So we will generate toString for
both of those, yeah?
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We're going to both of those.
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Okay well that's one way to do it.
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Well look, it remembered to do
the override for us, which we learned.
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The override annotation.
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And if we wanted to change this to make
our own template, we could, right?
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So let's go ahead and I'm gonna undo that,
and we will again, Generate toString.
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Up here there's these templates and
we had talked about that a little bit.
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So there's different
options that you could do.
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You can also make a new one,
if you wanted to.
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If you want to come here
you can add a new template.
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Okay, and if you really feel like nerding
out that's something that you can do.
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To make it read however you want to,
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to be the default it will automatically
generate the same looking toString.
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The cool thing is when you save this it
will be saved into the project file so
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everybody else can use
the same toString format.
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I think we're fine with
the final string concatenation.
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Or let's.
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Yeah, I think that's fine.
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Okay.
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Great.
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Okay, so one thing that we didn't
talk about before is equals.
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And you can actually override
the equals method and
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this pretty much should be done on every
class that we create that we plan to use,
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especially ones that we
use in the collections.
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Now one reason that I didn't show you
how to do this in the last course
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is because it's much easier to
have the IDE do it for you.
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Ready let's do it and
then we'll chat about it.
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Okay?
So, I'm gonna do,
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again, Cmd+N and I'm gonna
generate the equals and hashCode.
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And let's just use the IntelliJ Default.
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And there's a couple of options here.
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I don't think we should use getters.
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We should use the private methods and
we will go over this in the future.
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Yeah, so we want both of these and
we want both of these in the hash code.
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And the non null fields.
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Let's not create one of
these without nulls.
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So, those are non nulls.
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Okay, so remember that using double
equals on objects just means
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that they point to
the same object in memory.
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So what we really want to write here is
we want to determine what equality means.
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In this case, if the same person asks for
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the same song,
I mean that's pretty much equal, right?
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It's sameish.
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So things like hash maps and hash sets
use a thing called the hash code.
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We talked about this a little bit.
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And under the covers,
it stores things sensibly.
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So it returns a uniquieish integer,
that follows the same logic that equals.
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So therefore, if you overwrite equals or
hash code, you should override them both.
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So let's both of those on the page.
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So basically,
this generated code just checks to see
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if things are equal in memory.
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Right, if they are the exact same object,
than of course they're equal.
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And then otherwise it just goes ahead and
does the casting that we had done before,
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and then it upcalls equals.
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And oh, look here.
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It's upcalling equals on Song.
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So, you know what we should probably do,
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we should probably go write the equals for
Song.
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So let's go over there to Song.
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So I wanna show you another option.
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So we could do Cmd+O.
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And this is basically doing searchable,
but this is only for classes.
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So if you have a whole bunch of classes,
this is kind of handy.
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Cmd+O is right in your module as well.
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So in the song, let's just go ahead and
let's generate equals and hashCode.
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And we'll do the same thing,
intelliJ default.
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All those fields are valid right?
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It's gonna be equal.
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Yeah, all of those are true in the hash
code and anybody could create one of these
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songs and it's possible that they could
put a null value in there, right?
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The absence of that, so I am going
to go ahead and leave those as null.
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Okay, so it's generated those for
us as well.
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So the hashCode always
looks a little bit strange.
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One thing that might look
a little bit weird to you and
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is a little bit new is this
thing called a ternary operator.
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So the way that this works is if
this is true then this happens.
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It returns whatever the result is,
if this is true.
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Otherwise, it returns whatever this is.
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Okay, so, pretty cute, right?
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I mean, sometimes it's the most
clear way to express things,
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but often, it proves less readable.
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You're bound to run into them, so
I'm glad that you got to see them, but
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I just wanted to let you know
about ternary operators.
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I'll put a link in the teacher's notes.
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Cool.
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So now we have our
generated code over here.
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I think we're ready to use it.
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>> I know, I know I owe you like
five more dunk tank balls for
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making you type all that stuff before.
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But how much do you appreciate it now?
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Right?
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There's a couple more code generation
tricks that we'll encounter in the next
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couple of videos.
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Remember, everything is customizable,
so you can make generated code adhere to
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whatever your team determines
to be the best practice.
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So, let's get this feature implemented.
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We're gonna need to do a little
refactoring to get there, but
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the IDE is gonna help us.
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