iiwi

iiwi makes setting up Core Data stack (NSPersistentContainer) very easy. In your app you will have to create Core Data model and subclass iiwiAccess with your own repositories. Each repository is responsible for creating, fetching and deleting one type of entity from your model. Every repository should have function for creating entity with set of arguments needed to fill all mandatory and optional properties. There is possibility query based on primary key. Its definition is achieved by implementing generic protocol.

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Installation

iiwi is available through CocoaPods. To install

it, simply add the following line to your Podfile:

pod 'iiwi'

Usage

First step in would be to add import iiwi statement

Then we need to initialize model by specifying its name and bundle where it can be found. iiwi.initialize(model: "iiwi", inBundle: .main)

There are also initializers which accept bundle identifier (when model is in Framework) or URL.

Repository

Accessing entities should be done via repositories. Their job is to create, fetch and delete entities.

Repository is generic class which requires specifying type of entity from model and primary key query.

class Repository<T: NSManagedObject, Q: PrimaryKeyQuery>

Creating entities

Creating entities is done via Creator<T> class. Creator is generic class which specifies type of entity it will create.

In order to create entity you have to call func create().

Primary key query

When entity has primary key we could simply describe how to fetch entity based on its name and type.

public protocol PrimaryKeyQuery {
    associatedtype EntityType: NSManagedObject
    associatedtype KeyIndexType

    var key: String { get }
    var keyPredicateFormat: String { get }
    var query: Query<EntityType> { get }
    func entity(with: KeyIndexType) -> EntityType?
}

As example here is implementation how to query entities based on id (INT64).

public class IdInt64Querable<T: NSManagedObject>: PrimaryKeyQuery {

    public typealias EntityType = T
    public typealias KeyIndexType = Int64

    public let key = "id"
    public let keyPredicateFormat = "id = %i"
    public let query: Query<T>

    init(context: NSManagedObjectContext) {
        self.query = Query<T>(context: context)
    }

}

In order to avoid implementing func entity(with: KeyIndexType) -> EntityType? there is extension you could use.

extension PrimaryKeyQuery {

    public func entity(with key: KeyIndexType) -> EntityType? {
        return query.entities(with: NSPredicate(format: keyPredicateFormat, argumentArray: [key]), fetchLimit: 1, sortDescriptors: nil)?.first
    }

}

In case where entity does not have primary key we should use NoPrimaryKeyQuerable query description.

Deleting entities

Deleting entities is done via Deletor<T> class. We could either delete one entity func delete(entity: T) or delete all entities func deleteAll().

iiwiAccess

All repositories for your model entities should be defined and initialized in your subclass of iiwiAccess. This class will be responsible for saving and performing operations on context (NSManagedObjectContext).

Example of iiwiAccess subclass

import CoreData
import iiwi

public class DatabaseAccess: iiwiAccess {
    let bookshelfs: BookshelfRepository
    let authors: AuthorRepository
    let books: BookRepository

    override init(withContext context: NSManagedObjectContext)     {
        self.bookshelfs = BookshelfRepository(context: context)
        self.authors = AuthorRepository(context: context)
        self.books = BookRepository(context: context)

        super.init(withContext: context)
    }

    public static let view: DatabaseAccess = {
        return  DatabaseAccess(withContext: iiwi.viewContext)
    }()

    static var newBackground: DatabaseAccess {
        return DatabaseAccess(withContext: iiwi.newBackgroundContext())
    }

}

Additional access

iiwi class provides public access to viewContext: NSManagedObjectContext so that it could be adjusted to your needs. Also there is function to create new background context func newBackgroundContext() -> NSManagedObjectContext.

Author

rogowskimark, [email protected]

License

iiwi is available under the MIT license. See the LICENSE file for more info.