Core Data: Fundamentals

Now that you understand the basics of how to customize and configure your entities with attributes, it’s time to do a challenge! In this challenge, you’ll add some additional attributes to the RocketLaunch entity.

I’m intentionally not specifying which attributes you need to add because in addition to adding the attributes I find it useful to run through the exercise of figuring out how to model an object from the real world. So, what attributes would you add to a RocketLaunch?

When you’re done join me and we’ll walk through my implementation together. Good luck!

Welcome back! Hopefully that wasn’t too hard! Let’s compare notes.

I decided to keep my RocketLaunch model fairly simple because these things can get very complicated very quickly.

The first thing you need to know about rocket launches, and arguably the most important, is whether you’ve viewed them or not! They’re so awesome to watch!. For that lets add

• an isViewed property that is of type Boolean.
• You certainly don’t want this to be an optional property so you can uncheck that box.

Earlier when we talked about default values I glossed over it. This is a good place to use it.

• By default all new rocket launches should have isViewed set to false. Why have rocket launches that are completed when you create it?

You’ll notice that instead of a text field there is a drop down for default value. Xcode is smart on occasion and can figure out that there can only be two types of default values for a boolean property. It’s not so smart to figure out that you’re using Swift apparently because instead of a true or false value you have Objective-C’s YES and NO. Let’s set this to NO.

Right below that you should see another checkbox - “Use Scalar Type”. In just a minute you’re going to generate the code to work with these entities, and when you do so, Core Data is going to make some choices about what the types of these attributes should be.

With this box unchecked Core Data is going to use objects to represent these values instead of the primitive data types that you normally work with. For example, with this box unchecked the type of this attribute in code would be NSNumber which is an Objective-C type that wraps around a value of 0 or 1 to represent a Boolean. With the box checked you’ll get the non object type instead which in this case is Bool.

• For the next attribute let’s add launchDate, which also should not be optional. You’re not going to be doing anything fancy with a date in this app but this gives us a chance to look at the different data types and the flexibility you get with Core Data. In addition to the options you’ve seen already you’ll notice that with dates you can specify a range to validate against. It is somewhat limited though and only accepts a static date range. If it were flexible you could set the minimum date to be greater than the date at which the rocket launch was created.

To round it off let’s add a few more attributes:

• notes of type String to the rocket launch,
• and launchpad, which is also of type String.
• Both of these can be optional; we may not know the exact launch pad or have notes to keep until we’ve watched the launch. That’s looks good for now.

If you added any other attributes that’s awesome; feel free to continue using your model but just keep in mind that the user interface is somewhat limited. In the next video let’s talk about managed object subclasses.