With our model reconfigured to accept a name value,

the next thing we need to do is allow the user to input their name in the app.

To do that, we're going to add a text field to the main page.

Since this is the main view, the one we configured using a storyboard,

let's continue there rather than adding it programatically.

So in the main.storyboard file with the first view controller selected.

Go to the object library in the utilities area and

we're going to drag out a text field component and place it in the main view.

Let's give it a few constraints to position it.

Now I might need to zoom in so that you can see this better.

I'm going to position this 24 points on either side from the main view

from the margins.

So from the add new constraints menu,

we'll select the left and right constraints and we'll specify those as 24.

I also want to put it 40 points above the start adventure button.

So I'll click the bottom constraint I'll say 40.

We'll add these 3 here and then over in the align menu,

I'm going to specify that I want to horizontally center this in the container,

add the constraint and finally to resolve all this ambiguity,

we'll hit the update frames button, there we go.

I should point out that while we're laying out things using auto layout

we're still specifically designing for the larger iOS devices.

If you go ahead and look in the iPhone SE simulator for

example, you'll see that this layout does not work at all on the smaller sizes,

and this is a pretty bad error.

Our layouts should always look good on all devices.

But we don't know sufficient Auto Layout concepts just yet.

We will in the future, though.

And once we have that down, we'll start designing for most if not all screens.

Okay, let's run the app and make sure that our text field looks good.

Okay, so we have an error here,

it says, cannot assign value of type String Page to tie page.

Since we're trying to run the app, we need to resolve this error here.

We change the story computed property Adventure to be a function now that

takes a name.

So let's call that for the time being and pass in a temporary hardcoded value.

Okay, let's run this.

Our text field looks good and you might not be able to see clearly on mine, but

it's right here.

There are a couple different ways we can interact with the text field.

The simplest way is to create an outlet and poke at the properties that we need.

UI text field, the backing class,

has a text property that stores any of the text that the user types into the field.

You should know, though, that this class is a lot more powerful than that and

can even send streaming updates to anyone listening.

We can figure out what the user is typing when the user is typing it

when they press the Delete key, and much more.

Now all that is too complex for our use cases, so we're going to keep it simple,

and just create an outlet.

So we'll go back to the main.storyboard file,

select the main view control, here the entry point.

Go to the assistant editor.

So we have the right file here only more room and

up of the top will create an output.

So control drag from the text field over and

we'll call this nameTextField, pretty simple.

Now that we have a text field and our model requires a name.

We can't start the story without a name.

So instead if someone does try to do that,

hit start adventure without providing a name will go ahead and throw an error.

So let's go back to the Page.swift file.

And in here let's add a new error type up at the very top

to model errors that can arise in our interactive adventure.

So we'll say enum AdventureError and this is going to be of type Error.

And it's going to be super simple we'll just have one case name, nameNotProvided.

Now we can through the name not provide an error if the user doesn't enter a name but

tries to hit started venture.

There's one issue don't only go to the point where this would happen.

Be prepared for Segue method.

This is where the user taps the start of venture button and we make that check.

The issue is that this method is not a throwing one

which means that we cannot propagate the error if it's thrown within here.

That's okay though, we don't want to propagate it.

We're simply going to handle the error right as it is thrown.

So we'll check to see if a name is provided when the user

hits the start adventure button and

then we'll figure out what we do in the event that it's right and wrong.

So right in here, so if the Segue is the start of venture segue,

what's not to do clause rather we'll do this right here.

So I'll say do and then first we unwrap the text property

using an if let statement, the text property on the name text field.

So we'll say if let name equal.

So remember that the user is going to type their text into the name text field.

So whatever we're trying to get this name that we want to check,

whether it exists or not before we run our adventure.

It's going to be in the text property on the name text field.

So we'll say if that name equal nameTextField.text and

open the body of the if let statement.

Now UI TextField text property is an optional property and

you can see that if you click here, it's an optional string.

So we need to unwrap this but

there's an annoying thing in that it also defaults to an empty string.

So at this point the string is empty so

we can't just assume that we have a name in here.

So what we need to do after we unwrap it is

check to see if it's just an empty string.

So if name equal an empty string, then the user hasn't typed a name.

So if this is the case we throw the adventure

error in the nameNotProvided case.

Now I need to put a double equals here.

Okay, so if this doesn't happen, then else will execute our segue code.

So I'll copy this, the page controllers segueing section where we assign the name,

and we'll put that inside the else clause,

except now instead of hard coding a name we have a name we can use.

Now we'll have one more error in here.

And when you click it it says the error is not

handled because this enclosing function is not declared as a throwing one.

That's okay.

For now we're going to add an empty catch block which should be right here.

So we'll say catch let error and we'll take a break here.

In the next video, we'll try and fix this error.