// OptionalExtensions.swift - Copyright 2024 SwifterSwift
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// MARK: - Methods
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public extension Optional {
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/// SwifterSwift: Get self of default value (if self is nil).
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///
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/// let foo: String? = nil
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/// print(foo.unwrapped(or: "bar")) -> "bar"
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///
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/// let bar: String? = "bar"
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/// print(bar.unwrapped(or: "foo")) -> "bar"
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///
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/// - Parameter defaultValue: default value to return if self is nil.
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/// - Returns: self if not nil or default value if nil.
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func unwrapped(or defaultValue: Wrapped) -> Wrapped {
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// http://www.russbishop.net/improving-optionals
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return self ?? defaultValue
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}
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/// SwifterSwift: Gets the wrapped value of an optional. If the optional is `nil`, throw a custom error.
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///
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/// let foo: String? = nil
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/// try print(foo.unwrapped(or: MyError.notFound)) -> error: MyError.notFound
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///
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/// let bar: String? = "bar"
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/// try print(bar.unwrapped(or: MyError.notFound)) -> "bar"
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///
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/// - Parameter error: The error to throw if the optional is `nil`.
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/// - Throws: The error passed in.
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/// - Returns: The value wrapped by the optional.
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func unwrapped(or error: any Error) throws -> Wrapped {
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guard let wrapped = self else { throw error }
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return wrapped
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}
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/// SwifterSwift: Runs a block to Wrapped if not nil.
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///
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/// let foo: String? = nil
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/// foo.run { unwrappedFoo in
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/// // block will never run since foo is nil
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/// print(unwrappedFoo)
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/// }
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///
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/// let bar: String? = "bar"
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/// bar.run { unwrappedBar in
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/// // block will run since bar is not nil
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/// print(unwrappedBar) -> "bar"
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/// }
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///
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/// - Parameter block: a block to run if self is not nil.
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func run(_ block: (Wrapped) -> Void) {
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// http://www.russbishop.net/improving-optionals
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_ = map(block)
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}
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/// SwifterSwift: Assign an optional value to a variable only if the value is not nil.
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///
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/// let someParameter: String? = nil
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/// let parameters = [String: Any]() // Some parameters to be attached to a GET request
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/// parameters[someKey] ??= someParameter // It won't be added to the parameters dict
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///
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/// - Parameters:
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/// - lhs: Any?
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/// - rhs: Any?
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static func ??= (lhs: inout Optional, rhs: Optional) {
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guard let rhs else { return }
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lhs = rhs
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}
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/// SwifterSwift: Assign an optional value to a variable only if the variable is nil.
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///
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/// var someText: String? = nil
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/// let newText = "Foo"
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/// let defaultText = "Bar"
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/// someText ?= newText // someText is now "Foo" because it was nil before
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/// someText ?= defaultText // someText doesn't change its value because it's not nil
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///
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/// - Parameters:
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/// - lhs: Any?
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/// - rhs: Any?
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static func ?= (lhs: inout Optional, rhs: @autoclosure () -> Optional) {
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if lhs == nil {
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lhs = rhs()
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}
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}
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}
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// MARK: - Methods (Collection)
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public extension Optional where Wrapped: Collection {
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/// SwifterSwift: Check if optional is nil or empty collection.
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var isNilOrEmpty: Bool {
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return self?.isEmpty ?? true
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}
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/// SwifterSwift: Returns the collection only if it is not nil and not empty.
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var nonEmpty: Wrapped? {
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return (self?.isEmpty ?? true) ? nil : self
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}
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}
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// MARK: - Methods (RawRepresentable, RawValue: Equatable)
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public extension Optional where Wrapped: RawRepresentable, Wrapped.RawValue: Equatable {
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// swiftlint:disable missing_swifterswift_prefix
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/// Returns a Boolean value indicating whether two values are equal.
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///
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/// Equality is the inverse of inequality. For any values `a` and `b`,
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/// `a == b` implies that `a != b` is `false`.
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///
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/// - Parameters:
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/// - lhs: A value to compare.
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/// - rhs: Another value to compare.
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@inlinable static func == (lhs: Optional, rhs: Wrapped.RawValue?) -> Bool {
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return lhs?.rawValue == rhs
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}
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/// Returns a Boolean value indicating whether two values are equal.
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///
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/// Equality is the inverse of inequality. For any values `a` and `b`,
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/// `a == b` implies that `a != b` is `false`.
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///
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/// - Parameters:
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/// - lhs: A value to compare.
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/// - rhs: Another value to compare.
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@inlinable static func == (lhs: Wrapped.RawValue?, rhs: Optional) -> Bool {
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return lhs == rhs?.rawValue
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}
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/// Returns a Boolean value indicating whether two values are not equal.
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///
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/// Inequality is the inverse of equality. For any values `a` and `b`,
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/// `a != b` implies that `a == b` is `false`.
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///
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/// - Parameters:
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/// - lhs: A value to compare.
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/// - rhs: Another value to compare.
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@inlinable static func != (lhs: Optional, rhs: Wrapped.RawValue?) -> Bool {
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return lhs?.rawValue != rhs
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}
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/// Returns a Boolean value indicating whether two values are not equal.
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///
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/// Inequality is the inverse of equality. For any values `a` and `b`,
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/// `a != b` implies that `a == b` is `false`.
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///
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/// - Parameters:
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/// - lhs: A value to compare.
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/// - rhs: Another value to compare.
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@inlinable static func != (lhs: Wrapped.RawValue?, rhs: Optional) -> Bool {
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return lhs != rhs?.rawValue
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}
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// swiftlint:enable missing_swifterswift_prefix
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}
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// MARK: - Operators
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infix operator ??=: AssignmentPrecedence
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infix operator ?=: AssignmentPrecedence
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