ImportableUniqueObject

public protocol ImportableUniqueObject : ImportableObject, Hashable

NSManagedObject subclasses that conform to the ImportableUniqueObject protocol can be imported from a specified ImportSource. This allows transactions to either update existing objects or create new instances this way:

class Person: NSManagedObject, ImportableObject {
    typealias ImportSource = NSDictionary
    typealias UniqueIDType = NSString
    // ...
}

dataStack.perform(
    asynchronous: { (transaction) -> Void in
        let json: NSDictionary = // ...
        let person = try transaction.importUniqueObject(
            Into<Person>(),
            source: json
        )
        // ...
    },
    completion: { (result) in
        // ...
    }
)

UniqueIDType
The data type for the entity’s unique ID attribute
Declaration
Swift

associatedtype UniqueIDType : ImportableAttributeType
uniqueIDKeyPath
The keyPath to the entity’s unique ID attribute
Declaration
Swift

static var uniqueIDKeyPath: String { get }
uniqueIDValue
The object’s unique ID value. The default implementation returns the value of the attribute pertained to by uniqueIDKeyPath

Important
It is the developer’s responsibility to ensure that the attribute value pertained by uniqueIDKeyPath is not nil during the call to uniqueIDValue.
Declaration
Swift

var uniqueIDValue: UniqueIDType { get set }


                    
                    
                    shouldInsert(from:in:)

Return true if an object should be created from source. Return false to ignore and skip source. The default implementation returns the value returned by the shouldUpdate(from:in:) implementation.

Declaration

Swift

static func shouldInsert(from source: ImportSource, in transaction: BaseDataTransaction) -> Bool

Parameters

`source`	the object to import from
`transaction`	the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.

Return Value

true if an object should be created from source. Return false to ignore.


                    
                    
                    shouldUpdate(from:in:)

Default implementation

Return true if an object should be updated from source. Return false to ignore and skip source. The default implementation returns true.

Default Implementation

Declaration

Swift

static func shouldUpdate(from source: ImportSource, in transaction: BaseDataTransaction) -> Bool

Parameters

`source`	the object to import from
`transaction`	the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.

Return Value

true if an object should be updated from source. Return false to ignore.


                    
                    
                    uniqueID(from:in:)

Return the unique ID as extracted from source. This method is called before shouldInsert(from:in:) or shouldUpdate(from:in:). Return nil to skip importing from source. Note that throwing from this method will cause subsequent imports that are part of the same importUniqueObjects(:sourceArray:) call to be cancelled.

Declaration

Swift

static func uniqueID(from source: ImportSource, in transaction: BaseDataTransaction) throws -> UniqueIDType?

Parameters

`source`	the object to import from
`transaction`	the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.

Return Value

the unique ID as extracted from source, or nil to skip importing from source.


                    
                    
                    didInsert(from:in:)

Implements the actual importing of data from source. This method is called just after the object is created and assigned its unique ID as returned from uniqueID(from:in:). Implementers should pull values from source and assign them to the receiver’s attributes. Note that throwing from this method will cause subsequent imports that are part of the same importUniqueObjects(:sourceArray:) call to be cancelled. The default implementation simply calls update(from:in:).

Declaration

Swift

func didInsert(from source: ImportSource, in transaction: BaseDataTransaction) throws

Parameters

`source`	the object to import from
`transaction`	the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.


                    
                    
                    update(from:in:)

Implements the actual importing of data from source. This method is called just after the existing object is fetched using its unique ID. Implementers should pull values from source and assign them to the receiver’s attributes. Note that throwing from this method will cause subsequent imports that are part of the same importUniqueObjects(:sourceArray:) call to be cancelled.

Declaration

Swift

func update(from source: ImportSource, in transaction: BaseDataTransaction) throws

Parameters

`source`	the object to import from
`transaction`	the transaction that invoked the import. Use the transaction to fetch or create related objects if needed.