DataStoreTransaction Structure Reference

public struct DataStoreTransaction : ~Copyable, DataItemExtractor

A DataStoreTransaction, a ~Copyable struct passed borrowing to a DataLayer.TransactionBlock given to DataLayer.transactionally(execute:).

It wraps a pending DataStore edit session, offering the write helpers (apply, put, putAll, remove, clear) and commit as synchronous methods.

It conforms to DataItemExtractor, so all the typed getters of that protocol (get(key:as:), getArray(key:of:), …) and of JSONPathExtractable (extract(path:as:), …) are available directly on the transaction, on top of the getDataItem(key:) read requirement.

Note

DataStoreTransaction is noncopyable and is passed borrowing to the TransactionBlock, so it cannot be copied, stored in a property, or captured by an escaping closure. It is only valid for the duration of the block.


                    
                    
                    apply(_:)

Applies an edit (DataStoreEdit.put or DataStoreEdit.remove) to the pending transaction.

The DataLayer will not be changed until the transaction is committed. Applying after commit does nothing.

Declaration

Swift

public func apply(_ edit: DataStoreEdit)

Parameter	Description
`edit`	The `DataStoreEdit` to be applied once the transaction is committed.


                    
                    
                    put(key:value:expiry:)

Adds a single key-value pair to the pending transaction.

The DataLayer will not be changed until the transaction is committed. Putting after commit does nothing.

Declaration

Swift

public func put(key: String, value: DataInput, expiry: Expiry)

Parameter	Description
`key`	The key to store the value under.
`value`	The `DataInput` to be stored.
`expiry`	The time frame for this data to remain stored.


                    
                    
                    putAll(dataObject:expiry:)

Adds all key-value pairs from the DataObject to the pending transaction.

The DataLayer will not be changed until the transaction is committed. Putting after commit does nothing.

Declaration

Swift

public func putAll(dataObject: DataObject, expiry: Expiry)

Parameter	Description
`dataObject`	A `DataObject` containing the key-value pairs to be stored.
`expiry`	The time frame for this data to remain stored.


                    
                    
                    remove(key:)

Adds the removal of an individual key to the pending transaction.

The DataLayer will not be changed until the transaction is committed. Removing after commit does nothing.

Declaration

Swift

public func remove(key: String)

Parameter	Description
`key`	The key to remove from the `DataLayer`.


                    
                    
                    remove(keys:)

Adds the removal of multiple keys to the pending transaction.

The DataLayer will not be changed until the transaction is committed. Removing after commit does nothing.

Declaration

Swift

public func remove(keys: [String])

Parameter	Description
`keys`	The list of keys to remove from the `DataLayer`.

clear()
Adds the removal of all the entries of the DataLayer to the pending transaction, before then adding any other key-value pair.

The DataLayer will not be changed until the transaction is committed. Clearing after commit does nothing.
Declaration
Swift

public func clear()


                    
                    
                    getDataItem(key:)

Reads the current, already committed, value for a key from the DataLayer.

Applied, but not committed, edits won’t be reflected in the value returned by this method.

This is the only read requirement of DataItemExtractor: all its other typed getters, such as get(key:as:), are derived from it.

Declaration

Swift

public func getDataItem(key: String) -> DataItem?

Parameter	Description
`key`	The key used to look up data in the `DataLayer`.

Return Value

The DataItem if one was found for the provided key.

getAll()
Reads a dictionary containing all the current, already committed, data in the DataLayer.

Applied, but not committed, edits won’t be reflected in the value returned by this method.
Declaration
Swift

public func getAll() -> DataObject
Return Value

A DataObject dictionary with all the data currently stored in the DataLayer.
keys()
Reads all the keys currently, already committed, stored in the DataLayer.

Applied, but not committed, edits won’t be reflected in the value returned by this method.
Declaration
Swift

public func keys() -> [String]
Return Value

A list of all string keys present in the DataLayer.
count()
Reads the number of entries currently, already committed, stored in the DataLayer.

Applied, but not committed, edits won’t be reflected in the value returned by this method.
Declaration
Swift

public func count() -> Int
Return Value

The count of all key-value pairs in the DataLayer.
commit()
Commits the pending edits. It will commit all the edits that were previously applied.

Committing more than once does nothing, even if the first commit had nothing to write or failed.

Throws
An error when the transaction fails.
Declaration
Swift

public func commit() throws