If you have spent enough time with SwiftUI, you have likely run into the dreaded ghost re-render: your view appears, nothing in your data model has visibly changed, but body fires twice. Recently, I embarked on a deep-dive investigation using LLDB, stack traces, and Self._printChanges() to uncover why a presented AlertContent view was evaluating its body twice upon Read more
If you spent any time building app persistence around Core Data over the last decade, you probably remember the model editor. Beyond visual entity mapping, one of its best features was property-level validation. You could click on a String attribute, type 1 into the Minimum Length box, or drop in a Regex pattern, and Read more
If you’ve built modals or alerts in SwiftUI, chances are high you started with the classic .alert(“Title”, isPresented: $isShowingAlert). It’s the default approach shown in most basic tutorials. However, as soon as your alert needs to display dynamic data or work with isolated Core Data child contexts and draft objects, the isPresented pattern quickly Read more
I wondered why NSPersistentStoreRemoteChange doesn’t contain any info about what process made the change. For example it isn’t possible to know if the change even was made by the current process or not. This would be useful so when you make a save you know if you can skip reloading Read more
Update 30/6/2022: I realised we shouldn’t be initing NSPredicate objects inside body so need a new approach. I was reading Paul Hudson’s article Dynamically filtering @FetchRequest with SwiftUI and thought I would share an improvement for declaring the singers @FetchRequest property that supports a dynamic predicate for filtering: FilteredList.swift ContentView.swift
Always wondered why NSFetchedResultsChangeUpdate is so buggy? The reason is Apple don’t actually use it in their own apps. Instead, what they do is have a UITableViewCell subclass with a custom property setter for the object where they add KVO for only the properties they are interested in updates to, Read more
There is a new, yet not very well-known way to override NSManagedObject properties without needing to manually call KVO methods willChangeValueForKey etc. This is achieved using dynamic accessors prefixed with managedObjectOriginal as follows: Department.h @interface Department : NSManagedObject @property (nullable, nonatomic, copy) NSString *name; @end Department.m @interface Department (DynamicAccessors) – (NSString Read more