? 策略(行为型模式)
对象有某个行为，但是在不同的场景中，该行为有不同的实现算法。策略模式：
定义了一族算法（业务规则）；
封装了每个算法；
这族的算法可互换代替（interchangeable）。
示例：
struct TestSubject {
let pupilDiameter: Double
let blushResponse: Double
let isOrganic: Bool
}
protocol RealnessTesting: AnyObject {
func testRealness(_ testSubject: TestSubject) -> Bool
}
final class VoightKampffTest: RealnessTesting {
func testRealness(_ testSubject: TestSubject) -> Bool {
return testSubject.pupilDiameter < 30.0 || testSubject.blushResponse == 0.0
}
}
final class GeneticTest: RealnessTesting {
func testRealness(_ testSubject: TestSubject) -> Bool {
return testSubject.isOrganic
}
}
final class BladeRunner {
private let strategy: RealnessTesting
init(test: RealnessTesting) {
self.strategy = test
}
func testIfAndroid(_ testSubject: TestSubject) -> Bool {
return !strategy.testRealness(testSubject)
}
}
用法
let rachel = TestSubject(pupilDiameter: 30.2,
blushResponse: 0.3,
isOrganic: false)
// Deckard is using a traditional test
let deckard = BladeRunner(test: VoightKampffTest())
let isRachelAndroid = deckard.testIfAndroid(rachel)
// Gaff is using a very precise method
let gaff = BladeRunner(test: GeneticTest())
let isDeckardAndroid = gaff.testIfAndroid(rachel)