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October 11, 2022 22:04
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| // MARK: Power of Extensions | |
| // [Swift Book](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html) | |
| // MARK: - [Extension Syntax](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID470) | |
| extension Bool { | |
| } | |
| // MARK: - [Computed Properties](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID152) | |
| extension Bool { | |
| var isFalse: Bool { self == false } | |
| } | |
| extension Array { | |
| var isNotEmpty: Bool { first != nil } | |
| } | |
| // MARK: - [Initializers](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID153) | |
| extension Bool { | |
| init(value: Int, equals otherValue: Int) { | |
| self = value == otherValue | |
| } | |
| } | |
| // MARK: - [Methods](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID154) | |
| extension Bool { | |
| mutating func flip() { | |
| self = .random() | |
| } | |
| } | |
| // MARK: - [Subscripts](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID156) | |
| extension Array { | |
| subscript(filter: (Element) -> Bool) -> Self { | |
| self.filter(filter) | |
| } | |
| } | |
| let filtered = Array([1, 2, 3])[ | |
| { value in | |
| value.isMultiple(of: 2) | |
| } | |
| ] | |
| // MARK: - [Nested Types](https://docs.swift.org/swift-book/LanguageGuide/Extensions.html#ID157) | |
| extension Bool { | |
| indirect enum Token { | |
| case equalTo, lessThan, greaterThan | |
| case or(Token, Token), and(Token, Token) | |
| func or(_ other: Token) -> Token { | |
| .or(self, other) | |
| } | |
| func and(_ other: Token) -> Token { | |
| .and(self, other) | |
| } | |
| func evaluate<Value: Comparable>( | |
| value: Value, | |
| otherValue: Value | |
| ) -> Bool { | |
| switch self { | |
| case .equalTo: return value == otherValue | |
| case .lessThan: return value < otherValue | |
| case .greaterThan: return value > otherValue | |
| case let .or(lhs, rhs): | |
| return lhs.evaluate(value: value, otherValue: otherValue) || | |
| rhs.evaluate(value: value, otherValue: otherValue) | |
| case let .and(lhs, rhs): | |
| return lhs.evaluate(value: value, otherValue: otherValue) && | |
| rhs.evaluate(value: value, otherValue: otherValue) | |
| } | |
| } | |
| } | |
| init(value: Int, is token: Token, _ otherValue: Int) { | |
| self = token.evaluate(value: value, otherValue: otherValue) | |
| } | |
| } | |
| // MARK: - [Adding Protocol Conformance with an Extension](https://docs.swift.org/swift-book/LanguageGuide/Protocols.html#ID277) | |
| import SwiftUI | |
| struct CoolView: View { | |
| var body: some View { | |
| Text("😎") | |
| // ... | |
| "😎" | |
| } | |
| } | |
| extension String: View { | |
| public var body: some View { Text(self) } | |
| } | |
| // MARK: - Generics and the Where Clause | |
| // [Extending a Generic Type](https://docs.swift.org/swift-book/LanguageGuide/Generics.html#ID185) | |
| // [Extensions with a Generic Where Clause](https://docs.swift.org/swift-book/LanguageGuide/Generics.html#ID553) | |
| extension Array where Element: Equatable { | |
| var isEqual: Bool { | |
| reduce(into: Self()) { partialResult, element in | |
| guard partialResult.contains(element).isFalse else { | |
| return | |
| } | |
| partialResult.append(element) | |
| } | |
| .count <= 1 | |
| } | |
| } |
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