If you want to follow along, you can download the source files at the bottom of this tutorial. Put this new code just before the end of the configure(commit:) method: You'll note that I used try? The records are first sorted by their last name and then by their age. Working with a one-to-one relationship is identical to working with attributes. You’ve already seen how NSPersistentContainer does a huge amount of set up work on your behalf. We'll also work more with predicates in the next few articles of this series. Get access to over one million creative assets on Envato Elements. Remember, we made the "name" attribute indexed, which makes it lightning fast for search. The latter is usually preferable, and is what we'll be doing here, but it's only possible when your changes are small enough that Core Data can perform the conversion correctly. © 2021 Envato Pty Ltd. Envato Tuts+ tutorials are translated into other languages by our community members—you can be involved too! It is act… In the first article of this series, we learned about the Core Data stack, the heart of a Core Data application. We can change this by adding a modifier like so: You can also create compound predicates using the keywords AND, OR, and NOT. To show that this worked, change your cellForRowAt method so that the detail text label contains the author name as well as the commit date, like this: You should be able to run the app now and see the author name appear after a moment, as Core Data merges the new data with the old. Once the files are generated you'll now have four files: two each for Author and Commit. Open Core_Data.xcdatamodeld, select the Person entity, and create a relationship named children. A sample project that we will be creating will be build with Xcode 9 and Swift 4. This means that newAddress is also written to the backing store as well as the relationships we just defined. Partial loading unlike UserDefaults. We then create an NSSortDescriptor object by invoking sortDescriptorWithKey:ascending:, passing in the attribute of the entity we'd like to sort by, first, and a boolean indicating whether the records need to be sorted in ascending or descending order. There is no need to tell Core Data that we've updated the relationship. Let's start with a simple example in which we see how to sort the results returned by a fetch request. Open the data model (Project38.xcdatamodeld) for editing, then click the Add Entity button. Add this just before the "Show all commits" action: There are three things that bear explaining in that code: Run your app now and the new filter should work. As stated in the Predicate Programming Guide, %K is a variable argument substitution for a key path while %@ is a variable argument substitution for an object value. This is a many-to-many relationship. We can achieve the same result by invoking setValue:forKey: on anotherPerson and passing in newPerson and @"spouse" as the arguments. Although it's fairly likely you'll see commits by him, it can't be guaranteed – I'm pretty sure that Apple give him a couple of days vacation each year. Awesome, right? Bart Jacobs runs Code Foundry, a mobile development company based in Belgium and writes about iOS and Swift development on Cocoacasts. Remove optionality from all five properties. The output should look similar to what is shown below. Also note that we always set the inverse of the relationship. for fetch() this time, because we don't really care if the request failed: it will still fall through and get caught by the if commitAuthor == nil check later on. An indexed attribute is one that is optimized for fast searching. Glossary             Create a new project and, for convenience, check Use Core Dataduring the setup of the project. We've created one-to-one, one-to-many, and many-to-many relationships. Core Data from Scratch: Managed Objects and Fetch Requests, Core Data from Scratch: NSFetchedResultsController, Adobe Photoshop, Illustrator and InDesign. If a relationship has an inverse relationship, then Core Data takes care of this automatically. You may be wondering why we didn't link newPerson to newAddress, because we did define an inverse relationship in our data model. Predicates also make it very easy to fetch records based on their relationship. Now that every commit has an author attached to it, I want to add one last filter to our changeFilter() method to show you just how clever NSPredicate is. Set the Person entity as the destination and set the spouse relationship as the inverse relationship. Let's update our data model to illustrate this. Remember that calling save: on a managed object context saves the state of the managed object context. Removing the Old Movie Struct. • Relationships – In the context of Core Data, relationships are the same as those in other relational database systems in that they refer to how one data object relates to another. >>. Broadly speaking you don’t want to make these kinds of model changes while you’re still learning Core Data, so once you’ve verified that it works I would suggest you use “Erase All Content and Settings" again in the simulator to make sure you have a clean foundation again. If you see duplicates in the output, then make sure to comment out the code we wrote earlier to create the records. In the Data Model inspector, change Type to be "To Many", which tells Core Data that each author has many Commits attached to it.

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