iphone - how to properly save into coredata one to many relationship - Stack Overflow
to write a tutorial about Core Data Relationships between Entities. faster tests, due to the predefined context and Core Data save method. It also touches on Core Data's benefits, terminology, versioning, migration, Here's a high level cheat-sheet you can use for reference as you learn Core Data , which and then the whole file be written back to disk when it is saved. The ability to organize data into entities structured with relationships is. Core Data is a framework, provided by Apple, to be used on actually save those changes, the persistent store remains unaltered. From the bottom option “Add Entity” you can add as many entities\tables your model needs to have. This will also update the relationship attribute on the entity “Task” to.
To start, go ahead and select the Main. It should look like the picture below. Next, we need to indicate to the Table View which object will be responsible to return objects for it.
When to use UserDefaults, Keychain, or Core Data
Going back to code, add the following instance and method into the ViewController. And with this we have a basic user interface to support this use case for Code Data. I will not extend all user interfaces to fulfill the entire model layer, but you have the idea how to propagate to additional view controllers.
Then add to your ViewController.Mastering iOS Core Data with Swift: Entity Relationship
To fetch objects from the database the best aproach, and the solution Apple wants us to use, is the NSFetchedResultsController. Fetched results controllers can fetch efficiently records from a predicate and a sort order. It can also monitor changes to objects in the associated managed object context, and report changes in the result sets to its delegate.
After creating it, we will use a var of the same type to access this fetched results controller instance. With this, we will only initialize the controller at the moment that var will be used, similiar to a lazy aproach.
The benefits of this are that we guarantee the instance will be initialized at the moment it will be used. And whenever a change occurs, the fetched results controller will call the method controllerDidChangeContent: Go ahead, include the method and call the reload data from the table view variable to refresh his data.
First the Table View will ask how many sections our data contains. Then the number of rows for each section. And the updated cell for each object. At this point, if you run the application, you will only see the user interface that we have created before. The longer people use an application, the more chance that word about the application will spread, thus increasing sales potential.
To avoid crashing updates while still providing default data, you need a good testing strategy. You should deploy an untouched App Store version of the application to your device, add some data, and then test the upgrade process thoroughly.
Not Using Multiple Contexts At a minimum, a Core Data implementation should have one context operating on the main thread. The user interface also operates on the main thread, so any slowdowns to the main thread will impact application responsiveness.
While it is easier to use only one context, performance issues can creep in unless your data set is extremely small. For example, if you wanted to generate photo thumbnails or import some data, the application would appear to lock up for the duration of these processes. Since iOS 5, managing multiple contexts has become a lot easier. You can now configure a context hierarchy and run some contexts in the foreground and others in the background.
HANPO'S NOTE: Core Data Relationship and Relationship Delete Rules
By positioning a background context as a parent of a foreground context, you can implement background save. By positioning a background context as a child of a foreground context, you can implement an import context that automatically updates the user interface as objects are imported. A key limitation of iCloud, however, is that its data is constrained to one iCloud account.
Because iCloud accounts are deeply intertwined with many aspects of user devices, it is not practical or recommended to share iCloud accounts. This means that iCloud cannot be used to collaborate. For example, assume a husband and wife wanted to contribute to the same shopping list.
One-to-Many and Many-to-Many Core Data Relationships
Beyond account limitations, iCloud has no support for ordered relationships and also limits your lightweight model migration. Historically it has been too unstable to trust with precious customer data. One of the key simplifications of iCloud under iOS 7 is the introduction of the fallback store.
This store allows a seamless transition between iCloud accounts and the toggling of iCloud Documents and Data.
Users can start using an app with iCloud even if they have no network connection, and they will be none the wiser as their data is merged with iCloud once the network is available.
Is the user signed in to iCloud? Does the user want to use iCloud with this application? Does the user want to merge their local data with iCloud? Storing large amount of data into UserDefaults could affect performance of your app significantly as the whole UserDefaults plist file is loaded into memory when your app launches.
- Avoiding Ten Big Mistakes iOS Developers Make with Core Data
- Beginner’s Guide to Core Data in Swift 4
- Core Data Relationships
As mentioned in Apple Documentation: Keychain Previously, we have explained that UserDefaults saves data into plist. Change the boolean value of "boughtProVersion" from false to true, or change the amount of coins. Don't ever store a boolean for checking if user has bought in-app purchase in UserDefaults! User can change it very easily without jailbreaking and get your goodies for free! This is where Keychain comes in, from Apple documentation: The keychain services API helps you solve this problem by giving your app a mechanism to store small bits of user data in an encrypted database called a keychain.
When you securely remember the password for them, you free the user to choose a complicated one. To simplify the usage of keychain, we can use some open source Keychain wrapper library like Keychain Access. The Keychain Access library has done a lot of under the hood operation for us. Data saved in Keychain can be accessed by multiple apps, provided that the data are created from the apps from the same developer.
This is how SSO Secure sign on, like you login in one app and then another app will auto login for you in iOS app works.