KeyedVariable.swift

/// A variable value containing data whether explicit decoding/encoding
/// is asked.
///
/// The `KeyedVariable` type forwards `Variable`
/// decoding/encoding, initialization implementations and only
/// decoding/encoding condition are customized.
struct KeyedVariable<Var: Variable>: ComposedVariable {
    /// The customization options for `KeyedVariable`.
    ///
    /// `KeyedVariable` uses the instance of this type,
    /// provided during initialization, for customizing code generation.
    struct Options {
        /// Whether variable needs to be decoded/encoded.
        ///
        /// `True` if `CodedAt` or `CodedIn` macro
        /// is attached to variable.
        let code: Bool
    }

    /// The value wrapped by this instance.
    ///
    /// The wrapped variable's type data is
    /// preserved and provided during initialization.
    let base: Var
    /// The options for customizations.
    ///
    /// Options is provided during initialization.
    let options: Options
}

extension KeyedVariable: ConditionalVariable where Var: ConditionalVariable {
    /// Whether the variable is to be decoded.
    ///
    /// Provides whether underlying variable value is to be decoded,
    /// if provided code option is set as `false` otherwise `true`.
    var decode: Bool? { options.code ? true : base.decode }
    /// Whether the variable is to be encoded.
    ///
    /// Provides whether underlying variable value is to be encoded,
    /// if provided code option is set as `false` otherwise `true`.
    var encode: Bool? { options.code ? true : base.encode }
}

extension KeyedVariable: PropertyVariable where Var: PropertyVariable {
    /// Whether the variable type requires `Decodable` conformance.
    ///
    /// Provides whether underlying variable type requires
    /// `Decodable` conformance and provided code option
    /// is set as `true`. Otherwise depends on whether
    /// underlying variable is to be decoded.
    var requireDecodable: Bool? {
        options.code ? base.requireDecodable : base.decode
    }
    /// Whether the variable type requires `Encodable` conformance.
    ///
    /// Provides whether underlying variable type requires
    /// `Encodable` conformance and provided code option
    /// is set as `true`. Otherwise depends on whether
    /// underlying variable is to be encoded.
    var requireEncodable: Bool? {
        options.code ? base.requireEncodable : base.encode
    }
}

extension KeyedVariable: InitializableVariable
where Var: InitializableVariable {
    /// The initialization type of this variable.
    ///
    /// Initialization type is the same as underlying wrapped variable.
    typealias Initialization = Var.Initialization
}

extension KeyedVariable: NamedVariable where Var: NamedVariable {}
extension KeyedVariable: ValuedVariable where Var: ValuedVariable {}
extension KeyedVariable: AssociatedVariable where Var: AssociatedVariable {}

extension KeyedVariable: DefaultPropertyVariable
where Var: DefaultPropertyVariable {}