class Person: CoreStoreObject {
    @Field.Stored("name")
    var name: String = ""
    
    @Field.Relationship("pets", inverse: \Dog.$master)
    var pets: Set<Dog>
}

dataStack = DataStack(
    xcodeModelName: "MyStore",
    migrationChain: ["MyStore", "MyStoreV2", "MyStoreV3"]
)

dataStack.addStorage(
    SQLiteStore(fileName: "MyStore.sqlite"),
    completion: { (result) -> Void in
        // ...
    }
)

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let person = transaction.create(Into<Person>())
        person.name = "John Smith"
        person.age = 42
    },
    completion: { (result) -> Void in
        switch result {
        case .success: print("success!")
        case .failure(let error): print(error)
        }
    }
)

let people = try dataStack.fetchAll(From<Person>())

let people = try dataStack.fetchAll(
    From<Person>()
        .where(\.age > 30),
        .orderBy(.ascending(\.name), .descending(.\age)),
        .tweak({ $0.includesPendingChanges = false })
)

let maxAge = try dataStack.queryValue(
    From<Person>()
        .select(Int.self, .maximum(\.age))
)

try CoreStoreDefaults.dataStack.addStorageAndWait()

let dataStack = DataStack(
    xcodeModelName: "MyModel", // loads from the "MyModel.xcdatamodeld" file
    migrationChain: ["MyStore", "MyStoreV2", "MyStoreV3"] // model versions for progressive migrations
)
let migrationProgress = dataStack.addStorage(
    SQLiteStore(
        fileURL: sqliteFileURL, // set the target file URL for the sqlite file
        configuration: "Config2", // use entities from the "Config2" configuration in the .xcdatamodeld file
        localStorageOptions: .recreateStoreOnModelMismatch // if migration paths cannot be resolved, recreate the sqlite file
    ),
    completion: { (result) -> Void in
        switch result {
        case .success(let storage):
            print("Successfully added sqlite store: \(storage)")
        case .failure(let error):
            print("Failed adding sqlite store with error: \(error)")
        }
    }
)

CoreStoreDefaults.dataStack = dataStack // pass the dataStack to CoreStore for easier access later on

class MyViewController: UIViewController {
    let dataStack = DataStack(xcodeModelName: "MyModel") // keep reference to the stack
    override func viewDidLoad() {
        super.viewDidLoad()
        do {
            try self.dataStack.addStorageAndWait(SQLiteStore.self)
        }
        catch { // ...
        }
    }
    func methodToBeCalledLaterOn() {
        let objects = self.dataStack.fetchAll(From<MyEntity>())
        print(objects)
    }
}

try dataStack.addStorageAndWait(
    InMemoryStore(
        configuration: "Config2" // optional. Use entities from the "Config2" configuration in the .xcdatamodeld file
    )
)

try dataStack.addStorage(
    InMemoryStore(
        configuration: "Config2
    ),
    completion: { storage in
        // ...
    }
)

let migrationProgress = dataStack.addStorage(
    SQLiteStore(
        fileName: "MyStore.sqlite",
        configuration: "Config2", // optional. Use entities from the "Config2" configuration in the .xcdatamodeld file
        migrationMappingProviders: [Bundle.main], // optional. The bundles that contain required .xcmappingmodel files
        localStorageOptions: .recreateStoreOnModelMismatch // optional. Provides settings that tells the DataStack how to setup the persistent store
    ),
    completion: { /* ... */ }
)

try dataStack.addStorageAndWait(SQLiteStore())

public protocol LocalStorage: StorageInterface {
    var fileURL: NSURL { get }
    var migrationMappingProviders: [SchemaMappingProvider] { get }
    var localStorageOptions: LocalStorageOptions { get }
    func dictionary(forOptions: LocalStorageOptions) -> [String: AnyObject]?
    func cs_eraseStorageAndWait(metadata: [String: Any], soureModelHint: NSManagedObjectModel?) throws
}

CoreStoreDefaults.dataStack = DataStack(
    xcodeModelName: "MyModel",
    bundle: Bundle.main,
    migrationChain: ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"]
)

class Animal: CoreStoreObject {
    // ...
}
class Dog: Animal {
    // ...
}
class Person: CoreStoreObject {
    // ...
}

CoreStoreDefaults.dataStack = DataStack(
    CoreStoreSchema(
        modelVersion: "V1",
        entities: [
            Entity<Animal>("Animal", isAbstract: true),
            Entity<Dog>("Dog"),
            Entity<Person>("Person")
        ]
    )
)

class Animal: CoreStoreObject {
    // ...
}
class Dog: Animal {
    // ...
}
class Person: CoreStoreObject {
    // ...
}

let legacySchema = XcodeDataModelSchema.from(
    modelName: "MyModel", // .xcdatamodeld name
    bundle: bundle,
    migrationChain: ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"]
)
let newSchema = CoreStoreSchema(
    modelVersion: "V1",
    entities: [
        Entity<Animal>("Animal", isAbstract: true),
        Entity<Dog>("Dog"),
        Entity<Person>("Person")
    ]
)
CoreStoreDefaults.dataStack = DataStack(
    schemaHistory: SchemaHistory(
        legacySchema + [newSchema],
        migrationChain: ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4", "V1"] 
    )
)   

typealias Animal = V2.Animal
typealias Dog = V2.Dog
typealias Person = V2.Person
enum V2 {
    class Animal: CoreStoreObject {
        // ...
    }
    class Dog: Animal {
        // ...
    }
    class Person: CoreStoreObject {
        // ...
    }
}
enum V1 {
    class Animal: CoreStoreObject {
        // ...
    }
    class Dog: Animal {
        // ...
    }
    class Person: CoreStoreObject {
        // ...
    }
}

CoreStoreDefaults.dataStack = DataStack(
    CoreStoreSchema(
        modelVersion: "V1",
        entities: [
            Entity<V1.Animal>("Animal", isAbstract: true),
            Entity<V1.Dog>("Dog"),
            Entity<V1.Person>("Person")
        ]
    ),
    CoreStoreSchema(
        modelVersion: "V2",
        entities: [
            Entity<V2.Animal>("Animal", isAbstract: true),
            Entity<V2.Dog>("Dog"),
            Entity<V2.Person>("Person")
        ]
    ),
    migrationChain: ["V1", "V2"]
)

try dataStack.addStorageAndWait(
    SQLiteStore(
        fileURL: sqliteFileURL,
        localStorageOptions: .allowSynchronousLightweightMigration
    )
}

let migrationProgress: Progress? = try dataStack.addStorage(
    SQLiteStore(
        fileName: "MyStore.sqlite",
        configuration: "Config2"
    ),
    completion: { (result) -> Void in
        switch result {
        case .success(let storage):
            print("Successfully added sqlite store: \(storage)")
        case .failure(let error):
            print("Failed adding sqlite store with error: \(error)")
        }
    }
)

migrationProgress?.setProgressHandler { [weak self] (progress) -> Void in
    self?.progressView?.setProgress(Float(progress.fractionCompleted), animated: true)
    self?.percentLabel?.text = progress.localizedDescription // "50% completed"
    self?.stepLabel?.text = progress.localizedAdditionalDescription // "0 of 2"
}

let dataStack = DataStack(migrationChain: 
    ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"])

let dataStack = DataStack(migrationChain: [
    "MyAppModel": "MyAppModelV3",
    "MyAppModelV2": "MyAppModelV4",
    "MyAppModelV3": "MyAppModelV4"
])

let dataStack = DataStack(migrationChain: nil)

do {
    let storage = SQLiteStorage(fileName: "MyStore.sqlite")
    let migrationTypes: [MigrationType] = try dataStack.requiredMigrationsForStorage(storage)
    if migrationTypes.count > 1
        || (migrationTypes.filter { $0.isHeavyweightMigration }.count) > 0 {
        // ... will migrate more than once. Show special waiting screen
    }
    else if migrationTypes.count > 0 {
        // ... will migrate just once. Show simple activity indicator
    }
    else {
        // ... Do nothing
    }
    dataStack.addStorage(storage, completion: { /* ... */ })
}
catch {
    // ... either inspection of the store failed, or if no mapping model was found/inferred
}

case lightweight(sourceVersion: String, destinationVersion: String)
case heavyweight(sourceVersion: String, destinationVersion: String)

let dataStack = DataStack(migrationChain: ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"])
_ = try dataStack.addStorage(
    SQLiteStore(
        fileName: "MyStore.sqlite",
        migrationMappingProviders: [
            XcodeSchemaMappingProvider(from: "V1", to: "V2", mappingModelBundle: Bundle.main),
            CustomSchemaMappingProvider(from: "V2", to: "V3", entityMappings: [.deleteEntity("Person") ])
        ]
    ),
    completion: { (result) -> Void in
        // ...
    }
)

let person_v2_to_v3_mapping = CustomSchemaMappingProvider(
    from: "V2",
    to: "V3",
    entityMappings: [
        .transformEntity(
            sourceEntity: "Person",
            destinationEntity: "Person",
            transformer: { (sourceObject: UnsafeSourceObject, createDestinationObject: () -> UnsafeDestinationObject) in
                
                if (sourceObject["isVeryOldAccount"] as! Bool?) == true {
                    return // this account is too old, don't migrate 
                }
                // migrate the rest
                let destinationObject = createDestinationObject()
                destinationObject.enumerateAttributes { (attribute, sourceAttribute) in
                
                if let sourceAttribute = sourceAttribute {
                    destinationObject[attribute] = sourceObject[sourceAttribute]
                }
            }
        ) 
    ]
)
SQLiteStore(
    fileName: "MyStore.sqlite",
    migrationMappingProviders: [person_v2_to_v3_mapping]
)

let dataStack = self.dataStack
dataStack.perform(
    asynchronous: { (transaction) -> Void in
        // make changes
    },
    completion: { (result) -> Void in
        // ...
    }
)

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        // ...
        if shouldCancel {
            try transaction.cancel()
        }
        // ...
    },
    completion: { (result) -> Void in
        if case .failure(.userCancelled) = result {
            // ... cancelled
        }
    }
)

dataStack.perform(
    asynchronous: { (transaction) -> Bool in
        // make changes
        return transaction.hasChanges
    },
    completion: { (result) -> Void in
        switch result {
        case .success(let hasChanges): print("success! Has changes? \(hasChanges)")
        case .failure(let error): print(error)
        }
    }
)

dataStack.perform(
    asynchronous: { (transaction) -> Int in
        // make changes
        return transaction.delete(objects)
    },
    success: { (numberOfDeletedObjects: Int) -> Void in
        print("success! Deleted \(numberOfDeletedObjects) objects")
    },
    failure: { (error) -> Void in
        print(error)
    }
)

let hasChanges = dataStack.perform(
    synchronous: { (transaction) -> Bool in
        // make changes
        return transaction.hasChanges
    }
)

dataStack.perform(
    synchronous: { (transaction) in
        let person = transaction.create(Into<Person>())
        person.name = "John"
    },
    waitForAllObservers: false
)
let newPerson = dataStack.fetchOne(From<Person>.where(\.name == "John"))
// newPerson may be nil!
// The DataStack may have not yet received the update notification.

let transaction = dataStack.beginUnsafe()
// make changes
downloadJSONWithCompletion({ (json) -> Void in

    // make other changes
    transaction.commit()
})
downloadAnotherJSONWithCompletion({ (json) -> Void in

    // make some other changes
    transaction.commit()
})

let person = transaction.create(Into<MyPersonEntity>())

let person = transaction.create(Into<MyPersonEntity>("Config1"))

let person = transaction.create(Into<MyPersonEntity>(nil))

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let person = transaction.create(Into<MyPersonEntity>())
        person.name = "John Smith"
        person.age = 30
    },
    completion: { _ in }
)

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let person = try transaction.fetchOne(
            From<MyPersonEntity>()
                .where(\.name == "Jane Smith")
        )
        person.age = person.age + 1
    },
    completion: { _ in }
)

let jane: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        // WRONG: jane.age = jane.age + 1
        // RIGHT:
        let jane = transaction.edit(jane)! // using the same variable name protects us from misusing the non-transaction instance
        jane.age = jane.age + 1
    },
    completion: { _ in }
)

let jane: MyPersonEntity = // ...
let john: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        // WRONG: jane.friends = [john]
        // RIGHT:
        let jane = transaction.edit(jane)!
        let john = transaction.edit(john)!
        jane.friends = NSSet(array: [john])
    },
    completion: { _ in }
)

let john: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        transaction.delete(john)
    },
    completion: { _ in }
)

let john: MyPersonEntity = // ...
let jane: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        try transaction.delete(john, jane)
        // try transaction.delete([john, jane]) is also allowed
    },
    completion: { _ in }
)

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        try transaction.deleteAll(
            From<MyPersonEntity>()
                .where(\.age > 30)
        )
    },
    completion: { _ in }
)

let jane: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let jane = transaction.edit(jane)!
        jane.age = jane.age + 1
    },
    completion: { _ in }
)

let jane: MyPersonEntity = // ...

dataStack.perform(
    asynchronous: { (transaction) -> MyPersonEntity in
        let jane = transaction.fetchExisting(jane)! // instance for transaction
        jane.age = jane.age + 1
        return jane
    },
    success: { (transactionJane) in
        let jane = dataStack.fetchExisting(transactionJane)! // instance for DataStack
        print(jane.age)
    },
    failure: { (error) in
        // ...
    }
)

var peopleIDs: [NSManagedObjectID] = // ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let jane = try transaction.fetchOne(
            From<MyPersonEntity>()
                .where(\.name == "Jane Smith")
        )
        jane.friends = NSSet(array: transaction.fetchExisting(peopleIDs)!)
        // ...
    },
    completion: { _ in }
)

let json: [String: Any] = // ...
person.name = json["name"] as? NSString
person.age = json["age"] as? NSNumber
// ...

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let json: [String: Any] = // ...
        try! transaction.importObject(
            Into<MyPersonEntity>(),
            source: json
        )
    },
    completion: { _ in }
)

typealias ImportSource = NSDictionary

typealias ImportSource = [String: Any]

typealias ImportSource = NSData

public protocol ImportableObject: AnyObject {
    typealias ImportSource
    static func shouldInsert(from source: ImportSource, in transaction: BaseDataTransaction) -> Bool
    func didInsert(from source: ImportSource, in transaction: BaseDataTransaction) throws
}

typealias ImportSource = [String: Any]

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let json: [String: Any] = // ...
        try! transaction.importObject(
            Into<MyPersonEntity>(),
            source: json
        )
        // ...
    },
    completion: { _ in }
)

func didInsert(from source: ImportSource, in transaction: BaseDataTransaction) throws {
    self.name = source["name"] as? NSString
    self.age = source["age"] as? NSNumber
    // ...
}

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let jsonArray: [[String: Any]] = // ...
        try! transaction.importObjects(
            Into<MyPersonEntity>(),
            sourceArray: jsonArray // make sure this is of type Array<MyPersonEntity.ImportSource>
        )
        // ...
    },
    completion: { _ in }
)

func didInsert(from source: ImportSource, in transaction: BaseDataTransaction) throws {
    self.name = source["name"] as? NSString
    self.age = source["age"] as? NSNumber
    // ...
    if self.name == nil {
        throw Errors.InvalidNameError
    }
}

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let jsonArray: [[String: Any]] = // ...

        try transaction.importObjects(
            Into<MyPersonEntity>(),
            sourceArray: jsonArray
        )
    },
    success: {
        // ...
    },
    failure: { (error) in
        switch error {
        case Errors.InvalidNameError: print("Invalid name")
        // ...
        }
    }
)

public protocol ImportableUniqueObject: ImportableObject {
    typealias ImportSource
    typealias UniqueIDType: ImportableAttributeType

    static var uniqueIDKeyPath: String { get }
    var uniqueIDValue: UniqueIDType { get set }

    static func shouldInsert(from source: ImportSource, in transaction: BaseDataTransaction) -> Bool
    static func shouldUpdate(from source: ImportSource, in transaction: BaseDataTransaction) -> Bool
    static func uniqueID(from source: ImportSource, in transaction: BaseDataTransaction) throws -> UniqueIDType?
    func didInsert(from source: ImportSource, in transaction: BaseDataTransaction) throws
    func update(from source: ImportSource, in transaction: BaseDataTransaction) throws
}

class var uniqueIDKeyPath: String {
    return #keyPath(MyPersonEntity.personID) 
}
var uniqueIDValue: Int { 
    get { return self.personID }
    set { self.personID = newValue }
}
class func uniqueID(from source: ImportSource, in transaction: BaseDataTransaction) throws -> Int? {
    return source["id"] as? Int
}

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let json: [String: Any] = // ...
        try! transaction.importUniqueObject(
            Into<MyPersonEntity>(),
            source: json
        )
        // ...
    },
    completion: { _ in }
)

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let jsonArray: [[String: AnyObject]] = // ...
        try! transaction.importUniqueObjects(
            Into<MyPersonEntity>(),
            sourceArray: jsonArray
        )
        // ...
    },
    completion: { _ in }
)

let people = try dataStack.fetchAll(From<MyPersonEntity>())

let people = try dataStack.fetchAll(From<MyPersonEntity>("Config1")) // ignore objects in persistent stores other than the "Config1" configuration

let person = try dataStack.fetchAll(From<MyPersonEntity>(nil))

var people = try dataStack.fetchAll(
    From<MyPersonEntity>(),
    Where<MyPersonEntity>("%K > %d", "age", 30) // string format initializer
)
people = try dataStack.fetchAll(
    From<MyPersonEntity>(),
    Where<MyPersonEntity>(true) // boolean initializer
)

let predicate = NSPredicate(...)
var people = dataStack.fetchAll(
    From<MyPersonEntity>(),
    Where<MyPersonEntity>(predicate) // predicate initializer
)

var people = try dataStack.fetchAll(
    From<MyPersonEntity>()
        .where(\.age > 30) // Type-safe!
)

var people = try dataStack.fetchAll(
    From<MyPersonEntity>()
        .where(\.age > 30 && \.gender == "M")
)

var mostValuablePeople = try dataStack.fetchAll(
    From<MyPersonEntity>(),
    OrderBy<MyPersonEntity>(.descending("rating"), .ascending("surname"))
)

var people = try dataStack.fetchAll(
    From<MyPersonEntity>()
        .orderBy(.descending(\.rating), .ascending(\.surname)) // Type-safe!
)

var orderBy = OrderBy<MyPersonEntity>(.descending(\.rating))
if sortFromYoungest {
    orderBy += OrderBy(.ascending(\.age))
}
var mostValuablePeople = try dataStack.fetchAll(
    From<MyPersonEntity>(),
    orderBy
)

var people = try dataStack.fetchAll(
    From<MyPersonEntity>(),
    Where<MyPersonEntity>("age > %d", 30),
    OrderBy<MyPersonEntity>(.ascending("surname")),
    Tweak { (fetchRequest) -> Void in
        fetchRequest.includesPendingChanges = false
        fetchRequest.returnsObjectsAsFaults = false
        fetchRequest.includesSubentities = false
    }
)

var people = try dataStack.fetchAll(
    From<MyPersonEntity>(),
        .where(\.age > 30)
        .orderBy(.ascending(\.surname))
        .tweak {
            $0.includesPendingChanges = false
            $0.returnsObjectsAsFaults = false
            $0.includesSubentities = false
        }
)

let johnsAge = try dataStack.queryValue(
    From<MyPersonEntity>(),
    Select<Int>("age"),
    Where<MyPersonEntity>("name == %@", "John Smith")
)

let allAges = try dataStack.queryAttributes(
    From<MyPersonEntity>(),
    Select("age")
)

let johnsAge = try dataStack.queryValue(
    From<MyPersonEntity>()
        .select(\.age) // binds the result to Int
        .where(\.name == "John Smith")
)

let oldestAge = try dataStack.queryValue(
    From<MyPersonEntity>(),
    Select<Int>(.maximum("age"))
)

let personJSON = try dataStack.queryAttributes(
    From<MyPersonEntity>(),
    Select("name", "age")
)

[
    [
        "name": "John Smith",
        "age": 30
    ],
    [
        "name": "Jane Doe",
        "age": 22
    ]
]

let personJSON = try dataStack.queryAttributes(
    From<MyPersonEntity>(),
    Select("name", .count("friends"))
)

[
    [
        "name": "John Smith",
        "count(friends)": 42
    ],
    [
        "name": "Jane Doe",
        "count(friends)": 231
    ]
]

let personJSON = try dataStack.queryAttributes(
    From<MyPersonEntity>(),
    Select("name", .count("friends", as: "friendsCount"))
)

[
    [
        "name": "John Smith",
        "friendsCount": 42
    ],
    [
        "name": "Jane Doe",
        "friendsCount": 231
    ]
]

let personJSON = try dataStack.queryAttributes(
    From<MyPersonEntity>(),
    Select("age", .count("age", as: "count")),
    GroupBy("age")
)

let personJSON = try dataStack.queryAttributes(
    From<MyPersonEntity>()
        .select(.attribute(\.age), .count(\.age, as: "count"))
        .groupBy(\.age)
)

[
    [
        "age": 42,
        "count": 1
    ],
    [
        "age": 22,
        "count": 1
    ]
]

public protocol CoreStoreLogger {
    func log(level level: LogLevel, message: String, fileName: StaticString, lineNumber: Int, functionName: StaticString)
    func log(error error: CoreStoreError, message: String, fileName: StaticString, lineNumber: Int, functionName: StaticString)
    func assert(@autoclosure condition: () -> Bool, @autoclosure message: () -> String, fileName: StaticString, lineNumber: Int, functionName: StaticString)
    func abort(message: String, fileName: StaticString, lineNumber: Int, functionName: StaticString)
}

CoreStoreDefaults.logger = MyLogger()

let observer = person.observe(\.age, options: [.new]) { (person, change)
    print("Happy \(change.newValue)th birthday!")
}

let observer = person.age.observe(options: [.new]) { (person, change)
    print("Happy \(change.newValue)th birthday!")
}

let objectPublisher: ObjectPublisher<Person> = person.asPublisher(in: dataStack)

let listPublisher: ListPublisher<Person> = // ...
// ...
let objectPublisher = listPublisher.snapshot[indexPath]

objectPublisher.addObserver(self) { [weak self] (objectPublisher) in
    let snapshot: ObjectSnapshot<Person> = objectPublisher.snapshot
    // handle changes
}

class MyViewController: UIViewController, ObjectObserver {
    func objectMonitor(monitor: ObjectMonitor<MyPersonEntity>, willUpdateObject object: MyPersonEntity) {
        // ...
    }
    
    func objectMonitor(monitor: ObjectMonitor<MyPersonEntity>, didUpdateObject object: MyPersonEntity, changedPersistentKeys: Set<KeyPathString>) {
        // ...
    }
    
    func objectMonitor(monitor: ObjectMonitor<MyPersonEntity>, didDeleteObject object: MyPersonEntity) {
        // ...
    }
}

let person: MyPersonEntity = // ...
self.monitor = dataStack.monitorObject(person)
self.monitor.addObserver(self)

let listPublisher = dataStack.listPublisher(
    From<Person>()
        .sectionBy(\.age") { "Age \($0)" } // sections are optional
        .where(\.title == "Engineer")
        .orderBy(.ascending(\.lastName))
)

listPublisher.addObserver(self) { [weak self] (listPublisher) in
    let snapshot: ListSnapshot<Person> = listPublisher.snapshot
    // handle changes
}

self.dataSource = DiffableDataSource.CollectionViewAdapter<Person>(
    collectionView: self.collectionView,
    dataStack: CoreStoreDefaults.dataStack,
    cellProvider: { (collectionView, indexPath, person) in
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PersonCell") as! PersonCell
        cell.setPerson(person)
        return cell
    }
)

// ...

listPublisher.addObserver(self) { [weak self] (listPublisher) in
   self?.dataSource?.apply(
       listPublisher.snapshot, animatingDifferences: true
   )
}

class MyViewController: UIViewController, ListObserver {
    func listMonitorDidChange(monitor: ListMonitor<MyPersonEntity>) {
        // ...
    }
    
    func listMonitorDidRefetch(monitor: ListMonitor<MyPersonEntity>) {
        // ...
    }
}

    func listMonitorWillChange(_ monitor: ListMonitor<MyPersonEntity>)
    func listMonitorDidChange(_ monitor: ListMonitor<MyPersonEntity>)
    func listMonitorWillRefetch(_ monitor: ListMonitor<MyPersonEntity>)
    func listMonitorDidRefetch(_ monitor: ListMonitor<MyPersonEntity>)

    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didInsertObject object: MyPersonEntity, toIndexPath indexPath: IndexPath)
    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didDeleteObject object: MyPersonEntity, fromIndexPath indexPath: IndexPath)
    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didUpdateObject object: MyPersonEntity, atIndexPath indexPath: IndexPath)
    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didMoveObject object: MyPersonEntity, fromIndexPath: IndexPath, toIndexPath: IndexPath)

    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didInsertSection sectionInfo: NSFetchedResultsSectionInfo, toSectionIndex sectionIndex: Int)
    func listMonitor(_ monitor: ListMonitor<MyPersonEntity>, didDeleteSection sectionInfo: NSFetchedResultsSectionInfo, fromSectionIndex sectionIndex: Int)

self.monitor = dataStack.monitorList(
    From<MyPersonEntity>()
        .where(\.age > 30)
        .orderBy(.ascending(\.name))
        .tweak { $0.fetchBatchSize = 20 }
)
self.monitor.addObserver(self)

let firstPerson = self.monitor[0]

self.monitor = dataStack.monitorSectionedList(
    From<MyPersonEntity>()
        .sectionBy(\.age)
        .where(\.gender == "M")
        .orderBy(.ascending(\.age), .ascending(\.name))
        .tweak { $0.fetchBatchSize = 20 }
)

self.monitor = dataStack.monitorSectionedList(
    From<MyPersonEntity>()
        .sectionBy(\.age) { (sectionName) -> String? in
            "\(sectionName) years old"
        }
        .orderBy(.ascending(\.age), .ascending(\.name))
)

func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    let sectionInfo = self.monitor.sectionInfoAtIndex(section)
    return sectionInfo.name
}

let indexPath = IndexPath(row: 2, section: 1)
let person1 = self.monitor[indexPath]
let person2 = self.monitor[1, 2]
// person1 and person2 are the same object

class Animal: CoreStoreObject {
    @Field.Stored("species")
    var species: String = ""
}

class Dog: Animal {
    @Field.Stored("nickname")
    var nickname: String?
    
    @Field.Relationship("master")
    var master: Person?
}

class Person: CoreStoreObject {
    @Field.Stored("name")
    var name: String = ""
    
    @Field.Relationship("pets", inverse: \Dog.$master)
    var pets: Set<Dog>
}

class Person: CoreStoreObject {
    @Field.Stored("name")
    private var internalName: String = ""
    // note property name is independent of the storage key name
}

CoreStoreDefaults.dataStack = DataStack(
    CoreStoreSchema(
        modelVersion: "V1",
        entities: [
            Entity<Animal>("Animal", isAbstract: true),
            Entity<Dog>("Dog"),
            Entity<Person>("Person")
        ]
    )
)
CoreStoreDefaults.dataStack.addStorage(/* ... */)

let keyPath = String(keyPath: \Dog.$nickname)

let puppies = try dataStack.fetchAll(
    From<Dog>()
        .where(\.$age < 5)
        .orderBy(.ascending(\.$age))
)

class Person: CoreStoreObject {
    
    struct CustomInfo: Codable {
        // ...
    }
    
    @Field.Coded("otherInfo", coder: FieldCoders.Json.self)
    var otherInfo: CustomInfo?
    
    @Field.Coded(
        "photo",
        coder: {
            encode: { $0.toData() },
            decode: { Photo(fromData: $0) }
        }
    )
    var photo: Photo?
}

// ❌
class Person: CoreStoreObject {

    @Field.Stored("identifier")
    var identifier: UUID = UUID() // Wrong!
    
    @Field.Stored("createdDate")
    var createdDate: Date = Date() // Wrong!
}

// ✅
class Person: CoreStoreObject {

    @Field.Stored("identifier", dynamicInitialValue: { UUID() })
    var identifier: UUID
    
    @Field.Stored("createdDate", dynamicInitialValue: { Date() })
    var createdDate: Date
}

CoreStoreSchema(
    modelVersion: "V1",
    entities: [
        Entity<Animal>("Animal", isAbstract: true),
        Entity<Dog>("Dog"),
        Entity<Person>("Person"),
    ],
    versionLock: [
        "Animal": [0x1b59d511019695cf, 0xdeb97e86c5eff179, 0x1cfd80745646cb3, 0x4ff99416175b5b9a],
        "Dog": [0xe3f0afeb109b283a, 0x29998d292938eb61, 0x6aab788333cfc2a3, 0x492ff1d295910ea7],
        "Person": [0x66d8bbfd8b21561f, 0xcecec69ecae3570f, 0xc4b73d71256214ef, 0x89b99bfe3e013e8b]
    ]
)

print(CoreStoreDefaults.dataStack.modelSchema.printCoreStoreSchema())

dataStack.reactive
    .addStorage(
        SQLiteStore(fileName: "core_data.sqlite")
    )
    .sink(
        receiveCompletion: { result in
            // ...
        },
        receiveValue: { (progress) in
            print("\(round(progress.fractionCompleted * 100)) %") // 0.0 ~ 1.0
            switch progress {
            case .migrating(let storage, let nsProgress):
                // ...
            case .finished(let storage, let migrationRequired):
                // ...
            }
        }
    )
    .store(in: &cancellables)

dataStack.reactive
    .perform(
        asynchronous: { (transaction) -> (inserted: Set<NSManagedObject>, deleted: Set<NSManagedObject>) in

            // ...
            return (
                transaction.insertedObjects(),
                transaction.deletedObjects()
            )
        }
    )
    .sink(
        receiveCompletion: { result in
            // ...
        },
        receiveValue: { value in
            let inserted = dataStack.fetchExisting(value0.inserted)
            let deleted = dataStack.fetchExisting(value0.deleted)
            // ...
        }
    )
    .store(in: &cancellables)

dataStack.reactive
    .importUniqueObjects(
        Into<Person>(),
        sourceArray: [
            ["name": "John"],
            ["name": "Bob"],
            ["name": "Joe"]
        ]
    )
    .sink(
        receiveCompletion: { result in
            // ...
        },
        receiveValue: { (people) in
            XCTAssertEqual(people?.count, 3)
            // ...
        }
    )
    .store(in: &cancellables)

listPublisher.reactive
    .snapshot(emitInitialValue: true)
    .sink(
        receiveCompletion: { result in
            // ...
        },
        receiveValue: { (listSnapshot) in
            dataSource.apply(
                listSnapshot,
                animatingDifferences: true
            )
        }
    )
    .store(in: &cancellables)

objectPublisher.reactive
    .snapshot(emitInitialValue: true)
    .sink(
        receiveCompletion: { result in
            // ...
        },
        receiveValue: { (objectSnapshot) in
            tableViewCell.setObject(objectSnapshot)
        }
    )
    .store(in: &tableViewCell.cancellables)

let people: ListPublisher<Person>

var body: some View {
   List {
       ListReader(self.people) { listSnapshot in
           ForEach(objectIn: listSnapshot) { person in
               // ...
           }
       }
   }
   .animation(.default)
}

let people: ListPublisher<Person>

var body: some View {
    ListReader(self.people, keyPath: \.count) { count in
        Text("Number of members: \(count)")
    }
}

let person: ObjectPublisher<Person>

var body: some View {
   ObjectReader(self.person) { objectSnapshot in
       // ...
   }
   .animation(.default)
}

let person: ObjectPublisher<Person>

var body: some View {
    ObjectReader(self.person, keyPath: \.fullName) { fullName in
        Text("Name: \(fullName)")
    }
}

let person: ObjectPublisher<Person>

var body: some View {
   ObjectReader(
       self.person,
       content: { objectSnapshot in
           // ...
       },
       placeholder: { Text("Record not found") }
   )
}

@ListState
var people: ListSnapshot<Person>

init(listPublisher: ListPublisher<Person>) {
   self._people = .init(listPublisher)
}

var body: some View {
   List {
       ForEach(objectIn: self.people) { objectSnapshot in
           // ...
       }
   }
   .animation(.default)
}

@ListState(
    From<Person>()
        .sectionBy(\.age)
        .where(\.isMember == true)
        .orderBy(.ascending(\.lastName))
)
var people: ListSnapshot<Person>

var body: some View {
    List {
        ForEach(sectionIn: self.people) { section in
            Section(header: Text(section.sectionID)) {
                ForEach(objectIn: section) { person in
                    // ...
                }
            }
        }
    }
    .animation(.default)
}

@ObjectState
var person: ObjectSnapshot<Person>?

init(objectPublisher: ObjectPublisher<Person>) {
   self._person = .init(objectPublisher)
}

var body: some View {
   HStack {
       if let person = self.person {
           AsyncImage(person.$avatarURL)
           Text(person.$fullName)
       }
       else {
           Text("Record removed")
       }
   }
}