02-12 Presenting the Dice View Controller

02-12 Presenting the Dice View Controller

Here we are in our
RollViewController.swift file.

And the first thing I want you to
do is delete any code that's in

the rollTheDice method.

Here in this method we're going to
present our custom view controller.

So how are we going to do that?

We might as well start by trying
to present it the same way we did

the ui kit view controllers.

So in that case we just construct our
DiceViewController and then present it.

Oh, but
also we need to set those dice values.

So we'll do that in these two lines.

Okay, let's see if it runs.

Okay, so far so good.

Oh, hm, got a problem.

What does the console say.

Okay.

Fatal error.

Unexpectedly found nil while
unwrapping an optional value.

Okay, so the green highlighting is
pointing to the first die property.

And we know if the first
die property is nil,

that's going to cause a runtime error.

Because first sty is
an implicitly unwrapped optional.

So why is first die nil?

If we look back at our object diagram,

we're reminded that these outlets to
our views were created in storyboard.

We created this instance of
DiceViewController without Storyboard so

that means these outlets, these views,
and this action don't exist yet.

So that's a problem.

So in order to get rid of this error
we need to get a fully assemble

DiceViewController from Storyboard.

So let's close the console and

then go back into our
rollViewControler.swf file.

So here's where we were presenting
our DiceViewController before in

the rollTheDice method.

You go ahead and delete this
reference to the DiceViewController,

and we're going to replace it.

In this line, first we get
a reference to a storyboard object.

And then we asked for

the DiceViewController by name,
using its storyboard identifier.

Let's take a closer look
at this new method,

instantiateViewControllerWithIdentifier.

This identifier is just a string.

It's the name that you give
the view controller in storyboard.

So let's double check that we
actually set that name in storyboard.

So if I open up the storyboard file and
click on the DiceViewController.

I can look in the utilities pane and
click on the identity inspector.

In the identity inspector, right here,
you'll see the storyboard identifier.

And we can see that yes, indeed,
it is set to DiceViewController.

Just for kicks, I'm going to go ahead
and delete this storyboard id and

the class id and

see what would happen if you forgot to
put the name of the view controller.

Now let's try and run it.

Okay?
So it compiles fine.

RollTheDice, oh,
terminating with uncaught exception.

Okay, so
if you get one of these exception errors

what you want to do is scroll
up to the top of the console and

then you'll get more
information about the error.

And here we can see
storyboard doesn't contain

a view controller with identifier,
DiceViewController.

So that's pretty much what we expected,
but we know how to fix that.

We'll just go back in the storyboard and
reset the name.

There, that ought to do it.

Now, lets go back into our
scrollViewController.swf

file, because I want to point
out one more thing about

that
instantiateViewControllerWithIdentifier.

What's going on at the end
of this line here,

where it says DiceViewController
as DiceViewController.

If you Alt click on this method,
you can see that it returns any object.

That's why we need to cast that returned
object as a DiceViewController.