Updating core data database


Now go to App Delegate file, you will see a pragma mark at the bottom that says Core Data Stack, if you worked with Core Data in the past you are probably surprised how compressed is now, and we have to thank Apple for that!In order to keep our code clean we are going to separate the Core Data implementation from the App Delegate, you can just keep it like it is and make a reference every time to your App Delegate when you need to, but a better way to do it is to create a different class to separate responsibilities, create a new file subclass of NSObject and name it Core Data Stack.Closures are great to handle Asynchronous calls because they are executed after the completion of a certain task, that’s why sometimes are named as completion handlers. ..it’s ok, just get the idea that you don’t need to create a specific enum for every type thank to generics. the definition is actually very simple and easy to understand.If a closure is passed as an argument to a function and it is invoked after the function returns, the closure is escaping.



If you are using Swift 3, you are probably going to find errors in your project if you miss the last step pointed by the blue arrow, just change the module to “Current Product Module” and the Codegen to “Manual/None” (I found this solution in Stack Overflow)Finally, in editor click on Create NSManaged Object Subclass, if you want I add a Model group in the project where you can save this new class (just to keep this organized but you don’t have to)Now, you have your class and if you go inside the file you will see that it don’t look like the ones that you are used to.When I am saying that we are going to create a Photo object you are probably thinking in create it by subclassing NSObject but what we need instead is an object subclass of NSManaged Object, this is a generic class that implements all the basic behavior required of a Core Data model object, its not that hard to implement so just follow along with me, start by opening the file with extension .xcdatamodeld in your bundle (it is where all your files are), click on it, it will open something like this.The red arrow points to the section where you need to add a name for your entity (entity is just a name for an object subclass of NSmanagedobject), type Photo.Here we are using the URLSession datatask with completion method to make a GET request to the server, inside it, we are using guard statements to handle potential errors, then we are using the JSONSerialization class to parse the data and downcast it into a dictionary.

Finally, you can see that we call the completion on the main thread, that’s because closures are executed Asynchronously, remember that, if not, your app can crash. Go to Photo VC and add this inside view Didload and run your app.

We are ready now for the second part of this post, Core Data.



Updating core data database comments


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    paulette60

    Feb 1, 2016. This chapter from Learning Core Data for iOS with Swift A Hands-On Guide to Building Core Data Applications, 2nd Edition shows how to add model versions and model mappings, and it demonstrates different migration techniques you can choose when upgrading a model.…
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    paulette60

    Mar 23, 2017. Core Data is a framework, provided by Apple, to be used on Applications for iOS and macOS. As Apple states, it is not a database, but instead a persistence framework that commonly uses SQLite to. This will also update the relationship attribute on the entity “Task” to “task”. By default the relationship is.…