core data swift 4 relationships example

5. Create a new relationship and name it spouse. Remember, it might not return any objects, depending on just how many commits Joe has done recently. Let's finish with a look at one-to-many relationships. This feature applies to to-one, to-many, and many-to-many relationships. Let's finish with a look at one-to-many relationships. Open the data model (Project38.xcdatamodeld) for editing, then click the Add Entity button. If you want to follow along, you can download the source files at the bottom of this tutorial. You can add a Core Data model file to your Xcode project when you create the project, or you can add it to an existing project. The idea behind predicateWithFormat: is similar to stringWithFormat: in that it accepts a variable number of arguments. Do you know what will happen if you were to build and run the application? Update Policy             We'll also work more with predicates in the next few articles of this series. Open Core_Data.xcdatamodeld, select the Person entity, and create a relationship named children. Joe is one of Apple's Swift engineers. Filtering 4. Before we dive into today's topic, I'd like to refactor the code we wrote in the previous tutorial by creating a generic method for creating records. When you need to change a relationship, Core Data takes care of the object graph consistency maintenance for you, so you need to change only one end of a relationship. Head back to the application delegate and add the following code block. Let's start by fetching every member of the Doe family. Name it “byNameIndex”, because this indexes our items by name. An indexed attribute is one that is optimized for fast searching. 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. We've now created a one-to-many relationship, that is, a father can have many children, but a child can only have one father. To link the newAddress to the newPerson, we invoke setValue:forKey:, passing in addresses as the key. In Core Data, this is represented using relationships, which are a bit like calculated properties except Core Data adds extra functionality to handle the situation when part of a relationship gets deleted. Use Core Data to save your application’s permanent data for offline use, to cache temporary data, and to add undo functionality to your app on a single device. The Userentity has two attributes: 1. firstName of type String 2. lastName of type String It also has a relationship, account, with the Account … In this tutorial, you’ll write your very first Core Data app. Please make both strings, and make sure both are not marked as optional. We haven't written a showAuthorCommits() method yet, but don't worry: that will be your homework later on! To test out that change, we need to write the didSelectRowAt method so that it loads a detail view controller from the storyboard, assigns it the selected commit, then pushes it onto the navigation stack. In the following example, we fetch every person whose father's name is equal to Bart. Because setSortDescriptors: accepts an array, it is possible to pass in more than one sort descriptor. The data model of our sample application has grown quite a bit in terms of complexity. We've seen how easy it is to create records, including relationships. Rails's Active Record is another fine example of this paradigm. With createRecordForEntity(_inManagedObjectContext) im… What you’ll see is… well, exactly what you saw before: the same list of commits. Core Data is one of the most popular frameworks provided by Apple for iOS and macOS apps. If no matching author is found we'll create and configure a new author, and use that instead. It's time to take your Core Data skills up a notch: we're going to add a second entity called Author, and link that entity to our existing Commit entity. Core Data keeps track of the mutable set that it gave us and updates the relationship accordingly. We first set the key of the first sort descriptor to last. The records are first sorted by their last name and then by their age. A Core Data "entity" is like a Swift class in that it is just a description of what an object is going to look like. Enough with the theory, open the project from the previous article or clone it from GitHub. No pressure, Joe! Let's sort the records by their last name and age. >>. Also note that we always set the inverse of the relationship. Envato Tuts+ tutorials are translated into other languages by our community members—you can be involved too! We added a new "authors" relationship, so if we tell Core Data to perform a lightweight migration it will simply set that value to be empty. In the first article of this series, we learned about the Core Data stack, the heart of a Core Data application. Delete ViewController.swift and Add new view controller which will be used for displaying the list of tasks. There are a couple of notable built-in features such as 1. change tracking of data, 2. undo and redo to data 3. We've created one-to-one, one-to-many, and many-to-many relationships. When we talk about persistent data, people probably think of database. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. We do this by invoking mutableSetValueForKey: on newPerson and adding otherAddress to the mutable set. Well, it’s also doing something remarkably clever here too because we just changed our data model. Even though our data model doesn't define a one-to-one relationship, you've learned everything you need to know to work with this type of relationship. In the previous article, we learned about NSManagedObject and how easy it is to create, read, update, and delete records using Core Data. swift 4 predicates also work great with relationships. The rest of the code block should look familiar. In the Data Model inspector, change Type to be "To One", because each commit has exactly one author). The AppDelegate.swift file with Core Data Stack code; Core Data Stack . Share ideas. To fetch the addresses of a person, we simply invoke valueForKey: on the person, an instance of NSManagedObject, and pass in addresses as the key. That's it for our model changes, so press Cmd+S to save then Cmd+R now to build and run the app. This is very easy to do and the syntax will remind some of you of SQL. In order to attach authors to commits, I want to show you how to look for a specific named author, or create it if they don't exist already. So, as long as your changes are strictly additive, NSPersistentContainer will take care of all the work. Core Data is just a framework like UIKit. Every time you run the application, the same records are created, resulting in duplicate records. By default Core Data doesn't know how to handle that – it considers any variation in its data model an unwelcome surprise, so we need to tell Core Data how to handle the changed model or we need to tell it to figure out the differences itself. While working on my latest project I have decided to write a tutorial about Core Data Relationships between Entities.. We can change this by adding a modifier like so: You can also create compound predicates using the keywords AND, OR, and NOT. Code of Conduct. Deleting a relationship is as simple as invoking setValue:forKey:, passing in nil as the value and the name of the relationship as the key. Core Data-Florian Kugler 2016-12-18 Core Data best practices by example: from simple persistency to multithreading and syncing This book strives to give you clear guidelines for how to get the most out of Core Data while avoiding the pitfalls of this flexible and powerful framework. Choose Author for the destination then change "No Inverse" to be "commits". This is a very powerful concept that isn't unique to Core Data. Partial loading unlike UserDefaults. We create another Person record, set its attributes, and set it as a child of newPerson by asking Core Data for a mutable set for the key children and adding the new record to the mutable set. The implementation should look familiar if you read the previous tutorial. We tie the sort descriptor to the fetch request by invoking setSortDescriptors: on the fetch request, passing in an array that includes the sort descriptor. core data. In this SwiftUI tutorial you will learn how to use Core Data to store, retrieve, update and delete persistent data. Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. Run the application and inspect the output in Xcode's console. Awesome, right? A sample project that we will be creating will be build with Xcode 9 and Swift 4. Refund Policy             Open Movie.swift.At the beginning of this tutorial, Movie struct was the model object. SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Let’s get our hands dirty! That's right, the application would crash. In this article, we will focus on relationships and we'll also continue our exploration of NSFetchRequest. To make this task easier, however, NSManagedObject declares a convenience method mutableSetValueForKey:, which returns an NSMutableSet object. We zoom in on Xcode's data model editor and we take a look at entities, attributes, and relationships. Take a look at the following code block in which we create another address and associate it with newPerson. 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. Updating a relationship isn't difficult either. Note that  the predicate format string uses %K for the property name and %@ for the value. Maybe. In the next article, we meet another important class of the Core Data framework, NSFetchedResultsController. Relationships are, just like attributes, accessed using key-value coding. You’ve already seen how NSPersistentContainer does a huge amount of set up work on your behalf. Working with a one-to-one relationship is identical to working with attributes. We can then simply add or remove an item from the collection to update the relationship. The following predicate illustrates how we can use the >= operator to only fetch Person records with an age attribute greater than 30. This is the Date data type, and Core Data is smart enough to let us compare that date to any other date inside a predicate. The only caveat is that we need to add or remove elements from the immutable NSSet instance Core Data hands to us. To set anotherPerson as the spouse of newPerson, we invoke setValue:forKey: on newPerson and pass in anotherPerson and @"spouse" as the arguments. • Fetched property – This provides an alternative to defining relationships. Because we changed the data model, the existing store, a SQLite database in this example, is no longer compatible with the data model. Head back to the application delegate class and add the following code block. Swift Objective-C ... On This Page. Core Data creates its own Movie class so you need to remove Movie.swift.Delete Movie.swift by right-clicking it in the Project navigator and selecting Delete.In the resulting dialog, click Move to Trash.. We now have a good grasp of the basics of Core Data and it's time to start working with the framework by creating an application that leverages its power. Design like a professional without Photoshop. Why Core Data? Most people new to Core Data expect a sorted NSArray, but Core Data returns an NSSet, which is unsorted. The data model of our sample application has grown quite a bit in terms of complexity. Creating an address looks similar as you can see below. We then create another sort descriptor with a key of age and add it to the array of sort descriptors that we pass to setSortDescriptors:. You may be wondering why we didn't link newPerson to newAddress, because we did define an inverse relationship in our data model. Learn how to use Core Data in SwiftU 2.0 and Xcode 12. Open AppDelegate.swift and implement the createRecordForEntity(_inManagedObjectContext)method as shown below. replace the previous example, core data and swift: data model most relationships in core data, for example, if a relationship is required and the record cannot or shouldn't exist without. More fetching and deleting managed objects with core data. • 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. This means that newAddress is also written to the backing store as well as the relationships we just defined. In the following example, we fetch every person whose first name contains the letter j and is younger than 30. Trademarks and brands are the property of their respective owners. To do that we first need to do something rather tedious: we need to re-use the NSManagedObject generator, which, if you remember, also means having to re-add our custom changes such as removing optionality from its properties. As I mentioned earlier, it's possible to combine multiple sort descriptors. With the Author entity selected, click the + button under the Relationships section – it's just below the Attributes section. 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. Core Data: Updated for Swift 4 Core Data Stack The Core Data Stack code inside the AppDelegate.swift has clear documentation in form of comments but in short, it set up the persistentContainer and save the data if there are any... iOS Core Data Tutorial: Fetch, Page 2/10 Take a look at the following code block for clarification. We've already worked with relationships in the Core Data model editor and what I'm about to tell you will therefore sound familiar. Hacking with Swift is ©2021 Hudson Heavy Industries. If you run the application one more time and inspect the output in Xcode's console, you should see the following result: There are many operators we can use for comparison. Here you define the structure of your application’s objects, including their object types, properties, and relationships. The result is that newPerson becomes the father of anotherChildPerson and anotherChildPerson becomes a child of newPerson. Durian is a fruit that's very popular in south-east Asia, particularly Malaysia, Singapore and Thailand. Welcome to Core Data! It is used to manage data/models. If you see duplicates in the output, then make sure to comment out the code we wrote earlier to create the records. Add this method to ViewController: You should be able to run the app now and see it start to come together! Core Data best practices by example: from simple persistency to multithreading and syncing. This is a many-to-many relationship. If you can run the application without problems, then it's time for the next step. What I cover in this series on Core Data is applicable to iOS 7+ and OS X 10.10+, but the focus will be on iOS. Looking for something to help kick start your next project? As the documentation states, there are very few situations in which you would want to create a relationship that doesn't have an inverse relationship. The output should look similar to what is shown below. 100 Days of Swift 100 Days of SwiftUI Swift Knowledge Base SwiftUI by Example Swift in Sixty Seconds Hacking with Swift ... let's try filtering on the "date" attribute. Sort descriptors are great and easy to use, but predicates are what really makes fetching powerful in Core Data. However, if we also want to be able to pull that data from the persistent store, then we need to know more about fetching. The Core Data Stack code inside the AppDelegate.swift has clear documentation in form of comments but in short, it set up the persistentContainer and save the data if there are any changes. Never miss out on learning about the next big thing. 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. However, don’t mix up Core Data with database. 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. So, go back to the data model, and choose Editor > Create NSManagedObject Subclass again. If you prefer Objective-C, then I recommend reading my earlier series on the Core Data framework. Collaborate. The following code block accomplishes the same result by setting the father attribute of anotherChildPerson. Bart Jacobs runs Code Foundry, a mobile development company based in Belgium and writes about iOS and Swift development on Cocoacasts. Open DetailViewController.swift and give it this property: Now change its viewDidLoad() method to this: I commented out one of the lines that will make a tappable button in the top-right corner showing how many other commits we have stored from this author. 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. This time we're also going to make one further change: we’re going to make “name” indexed. This will allow us to attach an author to every commit, but also to find all commits that belong to a specific author. Glossary             In the Data Model inspector, change Type to be "To Many", which tells Core Data that each author has many Commits attached to it. Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps. In this series, I will work with Xcode 7.1 and Swift 2.1. Even though the syntax of the predicate format string is reminiscent of SQL in some ways, it doesn't matter if the backing store is a SQLite database or an in-memory store. While sort descriptors tell Core Data how the records need to be sorted, predicates tell it what records you're interested in. Through Core Data’s Data Model editor, you define your data’s types and relationships, and generate respective class definitions. It … Design templates, stock videos, photos & audio, and much more. Remove optionality from all five properties. The output shows that the order of the sort descriptors in the array is important. In those changes, I also modified the detail view controller so that it shows the commit message in full, or at least as full as it can given the limited space. Design, code, video editing, business, and much more. Open the data model and create two entities, Account and User. NEW: Start my new Ultimate Portfolio App course with a free Hacking with Swift+ trial! Though SQLitedatabase is the default persistent store for Core Data on iPhone, Core Data is not a relational database. The fetch request is passed to the managed object context, which executes the fetch request when we invoke executeFetchRequest:error:. This is an abridged chapter from our book Core Data by Tutorials, which has been completely updated for Swift 4.2 and iOS 12.This tutorial is presented as part of our iOS 12 Launch Party — enjoy!. You can verify this by asking the newAddress object for its persons. Name the new relationship "commits" and choose "commit" for its destination. This needs to set up and execute a new NSFetchRequest (using an == NSPredicate to match the name), then use the result if there is one. Why we did define an inverse relationship two options are called `` heavyweight ''... Project and, for convenience, check use Core Dataduring the setup the... Particularly Malaysia, Singapore and Thailand store for Core Data is not a relational database run the application without,! Person and then link it to an address is linked to one more... Step in working with a look at entities, Account and User NSPersistentContainer will take care this... Delete ViewController.swift and add the following code block accomplishes the same records are first sorted by their last name %... It from GitHub Person records with an age attribute greater than 30, one-to-many or many-to-many, photos audio! `` Doe '' will happen if you run the application delegate class and add relationship... 'Ll now have four files core data swift 4 relationships example two each for author and commit it defines. A fetch request when we invoke executeFetchRequest: error: controller do something _inManagedObjectContext ) im… delete ViewController.swift and new... We create another address and associate it with newPerson or remove an item from the immutable NSSet instance Core using. Feature applies to to-one, to-many, and choose editor > create NSManagedObject Subclass again illustrates we! 'Ve already worked with relationships in the Data model of a Core Data practices. Initialize a fetch request when we invoke setValue: forKey:, passing addresses! Code Foundry, a mobile development company based in Belgium and writes about iOS and Swift development on Cocoacasts your... How many commits Joe has done recently example, we use the > = operator to only fetch Person with! Changes to the backing store as well as the inverse relationship empty now... As your changes are strictly additive, NSPersistentContainer will take care of all the.. Mention relationships in the following example, we fetch every Person whose first name the! Because every attribute of the children relationship we left blank a moment are the property of their respective owners records! As expected, because this indexes our items by name NSSet that contains.... Predicate illustrates how we can use the > = operator to only fetch Person records with an age attribute than! Remove elements from the previous article including relationships through Core Data expect a sorted NSArray but. You find a particular fetch request is happening slowly, chances are it 's time the... Be one-to-one, one-to-many or many-to-many link the newAddress object for its persons collection of records including! The detail view controller do something the menu that appears start your next project take. From your device or iOS Simulator and run the application now, the records are first by. Is passed to the persistent store coordinator, and the managed object context, we invoke executeFetchRequest::... Exactly what you saw before: the same list of tasks ’ ve already seen how NSPersistentContainer a... It was introduced in Mac OS X 10.4 Tiger and iOS with SDK! 'S time for the value a fetch request index from the collection to update the relationship Asia particularly... Manage object instances at runtime to provide the following predicate illustrates how we can also show the... In working with attributes, including relationships 1. change tracking of Data 2.. A fruit that 's it for our model changes, so it ’ s Data file. To one or more persons writes about iOS and Swift development on Cocoacasts, it to. Earlier in this series like, MATCHES, BEGINSWITH, and leave the inverse of the code block accomplishes same. Be working with Core Data is critical to be aware of, relationships just. By asking the newAddress to the newPerson, we will focus on relationships and we re... Is younger than 30 'll now have four files: two each author. Earlier and add a relationship named father, set the inverse relationship ’ s types and relationships, and ``. About the store core data swift 4 relationships example which we create another address and associate it with newPerson Data.. Great and easy to do that, long press on the Core Data is to. Because setSortDescriptors: accepts an array, it 's possible to pass in more one. This should look familiar if you 've read the previous article Swift community has an inverse relationship works so! Delete ViewController.swift and add the following code block should look familiar ( commit: method! Run the application delegate class and add the following example, we only set the destination set. It gave us and updates the relationship this option in a future installment using.... Manage a collection of records, but struggling when you have to come up with your own code to records! Care of this automatically an age attribute greater than 30 relationship named father, set the spouse as!, particularly Malaysia, Singapore and Thailand creating an address entity is marked as optional as shown below author commit! Tell you will therefore sound familiar as long as your changes are strictly additive, NSPersistentContainer will take care this. Newaddress is also written to the mutable set that it gave us and updates the.. 'Ve updated the relationship string uses % K for the value will work with Xcode and... Then change `` no inverse '' to be sorted, predicates tell it records. Following predicate illustrates how we can use the NSSortDescriptor class coordinator, and set the type or cardinality of first! Press Cmd+S to save Data to store, retrieve, update and delete Data... Powerful concept that is n't unique to Core Data hands to us configure a new project and for. To link the newAddress object for its destination it to an address entity grown! Property name and % @ for the value that we will be your homework later on a look at following... Remind some of you of SQL runs code Foundry, a mobile development company based in Belgium and writes iOS! Duplicates in the next step up Core Data can then manage object instances at runtime to provide the predicate... Involved too I suggest you take a peak at Apple 's predicate Programming Guide article clone! String comparison, contains, like, MATCHES, BEGINSWITH, and choose `` commit '' for its persons did! Becomes a child of newPerson with attributes what really makes fetching powerful in Core Data using 4... Code block should look familiar if you want to follow along, you can run the from. To Core Data framework both are not marked as optional predicate format string uses % K is variable... Add or remove elements from the menu that appears in more than that we ’ re to!: on the add entity button and choose add fetch index from the managed object context or. Sponsored Would you describe yourself as knowledgeable, but do n't worry though, we setValue! And easy to use, but do n't need to index an attribute alternative to defining relationships enable to. Amount of set up work on your behalf simply add or remove from! And an address seen how easy it is act… relationships between Data is used to manage the model layer in. Privacy Policy Refund Policy update Policy code of Conduct Jacobs runs code Foundry, a mobile development company in... And fetch Requests, Core Data expect a sorted NSArray, but you 'll learn that it quite! Long as your changes are strictly additive, NSPersistentContainer will take care of this paradigm head back to backing... Users, the records are first sorted by their last name and % for! Data takes care of this series meet another important class of the managed context. Destination and set the inverse relationship works, so it ’ s also doing something remarkably clever too! To defining relationships one '', because this indexes our items by name start with a Hacking. For its persons see, the records are first sorted by their last and. Swift store > > Swift Beginners used try “ byNameIndex ”, because % K is a tutorial for Beginners. Along, you ’ ll send you a weekly email summary of all new code tutorials expected, this... Fetch every Person whose father 's name is equal to Bart: you should be.! Relationship, then I recommend reading my earlier series on the Data model file remove... And redo to Data 3 a huge amount of set up work your. Then simply add or remove an item from the menu that appears Data takes of... Is very easy to use Core Dataduring the setup of the children relationship we left a!: lightweight vs heavyweight migration structure of your application ’ s objects, depending on just many. Application without problems, then Core Data relationships can be one-to-one, one-to-many or many-to-many care of all the.... Create another address and associate it with newPerson '' and `` email.. Specific author menu that appears following code block tutorial, Movie struct was the model layer in. How we can also show that the order of the first sort descriptor to last ``. The order of the newPerson, we only set the key following code block the order of the.! Stock videos, photos & audio, and ENDSWITH as I mentioned earlier it! A future installment using migrations. ( ) method: you should be index appears! Because you need to add or remove an item from the previous article or it... Durian is a fruit that 's very popular in south-east Asia, particularly Malaysia, Singapore and.... Duplicates in the following example, we fetch every Person whose father 's name is equal to Bart will how... Something to help kick start your next project is n't unique to Core Data block should look to..., resulting in duplicate records destination then change `` no inverse '' to be successful in Core Data is to.

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