SafeFetching

This library offers a DSL (Domain Specific Language) to safely build predicates and requests to fetch a CoreData store.

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Convenient and Safe Fetching

The library requires to manually define the entity class. Then the macro FetchableManagedObject can be used.

@FetchableManagedObjectfinalclassUser:NSManagedObject{@NSManagedvarscore=0.0@NSManagedvarname:String?=""}

This makes User conform to Fetchable and ready to be used with the SafeFetching API.

Then it's possible to use the DSL to build a request. The last step can either get the built request as NSFetchRequest<User> or execute the request in the provided context.

User.request().all(after:10).where{ $0.score >=15 || $0.name !="Joe"}.sorted(by:.ascending(\.score),.descending(\.name)).setting(\.returnsDistinctResults, to:true).nsValue // returns NSFetchRequest<User>

User.request().all(after:10).where{ $0.score >=15 || $0.name !="Joe"}.sorted(by:.ascending(\.score),.descending(\.name)).setting(\.returnsDistinctResults, to:true).fetch(in: context) // returns [User]

Advanced NSPredicate operators are also available like BEGINSWITH (hasPrefix).

User.request().all().where{ $0.name.hasPrefix("Do", options:.caseInsensitive)}.nsValue

More about predicates in the documentation.

Convenience for NS types

The library also offers convenience functions to set a predicate of a NSFetchRequest.

request.predicate =.safe(on:User.self){ $0.score.isIn(10...20)}
// or
request.predicate =.safe(on:User.self){(10...20).contains($0.score)}

NSPredicate, Predicate

Why not using the Predicate macro? Two reasons.

• It works only with SwiftData as of today (so iOS 17+, macOS 14+ ...). It doesn't work with CoreData.
• It doesn't support everything that NSPredicate does when fetching a CoreData store.

Meanwhile, NSPredicate requires to write everything in a String, which is very error-prone.

Whereas this library tries to cover three objectives:

1. Use compiler-checking to evaluate predicates and avoid runtime errors.
2. Writing a request and especially a predicate should feel as natural as possible in Swift.
3. No feature of NSPredicate to fetch a CoreData store should be left behind.