KeyValueStorage Protocol Reference

Key

A key is the identifier for a specific value stored in the key-value storage. The key is unique.

Declaration

Swift

typealias Key = String

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                    Value

A value can contain arbitrary data and is identified by a key.

Declaration

Swift

typealias Value = Bytes

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                    store(value:for:finished:)

Store a value in the key-value storage for a given key.

Example

storage.store(key: "name", value: Data("John Doe".utf8)) {
    optionalError in

    if let error = optionalError {
        // TODO Handle error
    }
}

Declaration

Swift

func store(value: Value, for key: Key, finished: @escaping (_ error: Error?) -> Void)

Parameters

`value`	The value that should be stored.
`key`	The key that identifies the value.
`finished`	A closure that is called asynchronuously once the operation is finished.
`error`	An optional error that might have occurred during storing.

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                    retrieve(for:finished:)

Retrieve a value from the key-value storage for a given key.

Example

storage.retrieve(for: "name") {
    optionalValue, optionalError in

    precondition((optionalValue != nil) == (optionalError != nil))

    guard let value = optionalValue else {
        let error = optionalError!
        // TODO Handle error
        return
    }

    // Success, do something with `value`
}

Postcondition

(value = nil) ⊻ (error = nil)

Declaration

Swift

func retrieve(for key: Key, finished: @escaping (_ value: Value?, _ error: Error?) -> Void)

Parameters

`key`	The key that identifies the value.
`finished`	A closure that is called asynchronuously once the operation is finished.
`value`	The value if no error occurred, `nil` else.
`error`	An optional error that might have occurred during storing.

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                    remove(for:finished:)

Remove the value from the key-value storage for a given key.

Example

storage.remove(key: "name") {
    optionalError in

    if let error = optionalError {
        // TODO Handle error
    }
}

Declaration

Swift

func remove(for key: Key, finished: @escaping (_ error: Error?) -> Void)

Parameters

`key`	The key that identifies the value.
`finished`	A closure that is called asynchronuously once the operation is finished.
`error`	An optional error that might have occurred during storing.

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