How to use spec method of is class

...9 *10 * Unless required by applicable law or agreed to in writing, software11 * distributed under the License is distributed on an "AS IS" BASIS,12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.13 * See the License for the specific language governing permissions and14 * limitations under the License.15 */16import ArgumentParser17import Foundation18private enum Constants {}19extension Constants {20  static let specDependencyLabel = "dependency"21  static let skipLinesWithWords = ["unit_tests", "test_spec"]22  static let dependencyLineSeparators = CharacterSet(charactersIn: " ,/")23  static let podSources = [24    "https://${BOT_TOKEN}@github.com/FirebasePrivate/SpecsTesting",25    "https://github.com/firebase/SpecsStaging.git",26    "https://cdn.cocoapods.org/",27  ]28  static let exclusivePods: [String] = ["FirebaseSegmentation"]29}30// flags for 'pod push'31extension Constants {32  static let flags = ["--skip-tests", "--allow-warnings"]33  static let umbrellaPodFlags = Constants.flags + ["--skip-import-validation", "--use-json"]34}35// SpecFiles is a wraper of dict mapping from required pods to their path. This36// will also contain a sequence of installing podspecs.37class SpecFiles {38  private var specFilesDict: [String: URL]39  var depInstallOrder: [String]40  var specSource: String41  init(_ specDict: [String: URL], from specSourcePath: String) {42    specFilesDict = specDict43    depInstallOrder = []44    specSource = specSourcePath45  }46  func removePod(_ key: String) {47    specFilesDict.removeValue(forKey: key)48  }49  subscript(key: String) -> URL? {50    return specFilesDict[key]51  }52  func contains(_ key: String) -> Bool {53    return specFilesDict[key] != nil54  }55  func isEmpty() -> Bool {56    return specFilesDict.isEmpty57  }58}59struct Shell {60  static let shared = Shell()61  @discardableResult62  func run(_ command: String, displayCommand: Bool = true,63           displayFailureResult: Bool = true) -> Int32 {64    let task = Process()65    let pipe = Pipe()66    task.standardOutput = pipe67    task.launchPath = "/bin/bash"68    task.arguments = ["-c", command]69    task.launch()70    if displayCommand {71      print("[SpecRepoBuilder] Command:\(command)\n")72    }73    task.waitUntilExit()74    let data = pipe.fileHandleForReading.readDataToEndOfFile()75    let log = String(data: data, encoding: .utf8)!76    if displayFailureResult, task.terminationStatus != 0 {77      print("-----Exit code: \(task.terminationStatus)")78      print("-----Log:\n \(log)")79    }80    return task.terminationStatus81  }82}83// Error types84enum SpecRepoBuilderError: Error {85  // Error occurs when circular dependencies are detected and deps will be86  // displayed.87  case circularDependencies(pods: Set<String>)88  // Error occurs when there exist specs that failed to push to a spec repo. All89  // specs failed to push should be displayed.90  case failedToPush(pods: [String])91  // Error occurs when a podspec is not found in the repo.92  case podspecNotFound(_ podspec: String, from: String)93}94struct SpecRepoBuilder: ParsableCommand {95  @Option(help: "The root of the firebase-ios-sdk checked out git repo.")96  var sdkRepo: String = FileManager().currentDirectoryPath97  @Option(help: "A list of podspec sources in Podfiles.")98  var podSources: [String] = Constants.podSources99  @Option(help: "Podspecs that will not be pushed to repo.")100  var excludePods: [String] = Constants.exclusivePods101  @Option(help: "Github Account Name.")102  var githubAccount: String = "FirebasePrivate"103  @Option(help: "Github Repo Name.")104  var sdkRepoName: String = "SpecsTesting"105  @Option(help: "Local Podspec Repo Name.")106  var localSpecRepoName: String107  @Flag(help: "Raise error while circular dependency detected.")108  var raiseCircularDepError: Bool = false109  // This will track down dependencies of pods and keep the sequence of110  // dependency installation in specFiles.depInstallOrder.111  func generateOrderOfInstallation(pods: [String], specFiles: SpecFiles,112                                   parentDeps: inout Set<String>) {113    // pods are dependencies will be tracked down.114    // specFiles includes required pods and their URLs.115    // parentDeps will record the path of tracking down dependencies to avoid116    // duplications and circular dependencies.117    // Stop tracking down when the parent pod does not have any required deps.118    if pods.isEmpty {119      return120    }121    for pod in pods {122      guard specFiles.contains(pod) else { continue }123      let deps = getTargetedDeps(of: pod, from: specFiles)124      // parentDeps will have all dependencies the current pod supports. If the125      // current pod were in the parent dependencies, that means it was tracked126      // before and it is circular dependency.127      if parentDeps.contains(pod) {128        print("Circular dependency is detected in \(pod) and \(parentDeps)")129        if raiseCircularDepError {130          Self131            .exit(withError: SpecRepoBuilderError132              .circularDependencies(pods: parentDeps))133        }134        continue135      }136      // Record the pod as a parent and use depth-first-search to track down137      // dependencies of this pod.138      parentDeps.insert(pod)139      generateOrderOfInstallation(140        pods: deps,141        specFiles: specFiles,142        parentDeps: &parentDeps143      )144      // When pod does not have required dep or its required deps are recorded,145      // the pod itself will be recorded into the depInstallOrder.146      if !specFiles.depInstallOrder.contains(pod) {147        print("\(pod) depends on \(deps).")148        specFiles.depInstallOrder.append(pod)149      }150      // When track back from a lower level, parentDep should track back by151      // removing one pod.152      parentDeps.remove(pod)153    }154  }155  // Scan a podspec file and find and return all dependencies in this podspec.156  func searchDeps(ofPod podName: String, from podSpecFiles: SpecFiles) -> [String] {157    var deps: [String] = []158    var fileContents = ""159    guard let podSpecURL = podSpecFiles[podName] else {160      Self161        .exit(withError: SpecRepoBuilderError162          .podspecNotFound(podName, from: podSpecFiles.specSource))163    }164    do {165      fileContents = try String(contentsOfFile: podSpecURL.path, encoding: .utf8)166    } catch {167      fatalError("Could not read \(podName) podspec from \(podSpecURL.path).")168    }169    // Get all the lines containing `dependency` but don't contain words we170    // want to ignore.171    let depLines: [String] = fileContents172      .components(separatedBy: .newlines)173      .filter { $0.contains("dependency") }174      // Skip lines with words in Constants.skipLinesWithWords175      .filter { !Constants.skipLinesWithWords.contains(where: $0.contains)176      }177    for line in depLines {178      let newLine = line.trimmingCharacters(in: .whitespacesAndNewlines)179      // This is to avoid pushing umbrellapods like Firebase/Core.180      let tokens = newLine.components(separatedBy: Constants.dependencyLineSeparators)181      if let depPrefix = tokens.first {182        if depPrefix.hasSuffix(Constants.specDependencyLabel) {183          // e.g. In Firebase.podspec, Firebase/Core will not be considered a184          // dependency.185          // "ss.dependency 'Firebase/Core'" will be splited in186          // ["ss.dependency", "'Firebase", "Core'"]187          let podNameRaw = String(tokens[1]).replacingOccurrences(of: "'", with: "")188          // In the example above, deps here will not include Firebase since189          // it is the same as the pod name.190          if podNameRaw != podName { deps.append(podNameRaw) }191        }192      }193    }194    return deps195  }196  // Filter and get a list of required dependencies found in the repo.197  func filterTargetDeps(_ deps: [String], with targets: SpecFiles) -> [String] {198    var targetedDeps: [String] = []199    for dep in deps {200      // Only get unique and required dep in the output list.201      if targets.contains(dep), !targetedDeps.contains(dep) {202        targetedDeps.append(dep)203      }204    }205    return targetedDeps206  }207  func getTargetedDeps(of pod: String, from specFiles: SpecFiles) -> [String] {208    let deps = searchDeps(ofPod: pod, from: specFiles)209    return filterTargetDeps(deps, with: specFiles)210  }211  func pushPodspec(forPod pod: String, sdkRepo: String, sources: [String],212                   flags: [String], shell: Shell = Shell.shared) -> Int32 {213    let podPath = sdkRepo + "/" + pod + ".podspec"214    let sourcesArg = sources.joined(separator: ",")215    let flagsArg = flags.joined(separator: " ")216    let outcome =217      shell218        .run(219          "pod repo push \(localSpecRepoName) \(podPath) --sources=\(sourcesArg) \(flagsArg)"220        )221    shell.run("pod repo update")222    return outcome223  }224  // This will commit and push to erase the entire remote spec repo.225  func eraseRemoteRepo(repoPath: String, from githubAccount: String, _ sdkRepoName: String,226                       shell: Shell = Shell.shared) {227    shell228      .run(229        "git clone --quiet https://${BOT_TOKEN}@github.com/\(githubAccount)/\(sdkRepoName).git"230      )231    let fileManager = FileManager.default232    do {233      let dirs = try fileManager.contentsOfDirectory(atPath: "\(repoPath)/\(sdkRepoName)")234      for dir in dirs {235        if dir != ".git" {236          shell.run("cd \(sdkRepoName); git rm -r \(dir)")237        }238      }239      shell.run("cd \(sdkRepoName); git commit -m 'Empty repo'; git push")240    } catch {241      print("Error while enumerating files \(repoPath): \(error.localizedDescription)")242    }243    do {244      try fileManager.removeItem(at: URL(fileURLWithPath: "\(repoPath)/\(sdkRepoName)"))245    } catch {246      print("Error occurred while removing \(repoPath)/\(sdkRepoName): \(error)")247    }248  }249  mutating func run() throws {250    let fileManager = FileManager.default251    let curDir = FileManager().currentDirectoryPath252    var podSpecFiles: [String: URL] = [:]253    let documentsURL = URL(fileURLWithPath: sdkRepo)254    do {255      let fileURLs = try fileManager.contentsOfDirectory(256        at: documentsURL,257        includingPropertiesForKeys: nil258      )259      let podspecURLs = fileURLs.filter { $0.pathExtension == "podspec" }260      for podspecURL in podspecURLs {261        let podName = podspecURL.deletingPathExtension().lastPathComponent262        if !Constants.exclusivePods.contains(podName) {263          podSpecFiles[podName] = podspecURL264        }265      }266    } catch {267      print(268        "Error while enumerating files \(documentsURL.path): \(error.localizedDescription)"269      )270    }271    // This set is used to keep parent dependencies and help detect circular272    // dependencies.273    var tmpSet: Set<String> = []274    print("Detect podspecs: \(podSpecFiles.keys)")275    let specFileDict = SpecFiles(podSpecFiles, from: sdkRepo)276    generateOrderOfInstallation(277      pods: Array(podSpecFiles.keys),278      specFiles: specFileDict,279      parentDeps: &tmpSet280    )281    print("Podspec push order:\n", specFileDict.depInstallOrder.joined(separator: "->\t"))282    do {283      if fileManager.fileExists(atPath: "\(curDir)/\(sdkRepoName)") {284        print("remove \(sdkRepoName) dir.")285        try fileManager.removeItem(at: URL(fileURLWithPath: "\(curDir)/\(sdkRepoName)"))286      }287      eraseRemoteRepo(repoPath: "\(curDir)", from: githubAccount, sdkRepoName)288    } catch {289      print("error occurred. \(error)")290    }291    var exitCode: Int32 = 0292    var failedPods: [String] = []293    for pod in specFileDict.depInstallOrder {294      var podExitCode: Int32 = 0295      print("----------\(pod)-----------")296      switch pod {297      case "Firebase":298        podExitCode = pushPodspec(299          forPod: pod,300          sdkRepo: sdkRepo,301          sources: podSources,302          flags: Constants.umbrellaPodFlags303        )304      default:305        podExitCode = pushPodspec(306          forPod: pod,307          sdkRepo: sdkRepo,308          sources: podSources,309          flags: Constants.flags310        )311      }312      if podExitCode != 0 {313        exitCode = 1314        failedPods.append(pod)315      }316    }317    if exitCode != 0 {318      Self.exit(withError: SpecRepoBuilderError.failedToPush(pods: failedPods))319    }...

...42    internal var isRunningAdditionalSuites = false43#else44    internal var isRunningAdditionalSuites = false45#endif46    private var specs: [String: ExampleGroup] = [:]47    private var sharedExamples: [String: SharedExampleClosure] = [:]48    private let configuration = Configuration()49    internal private(set) var isConfigurationFinalized = false50    internal var exampleHooks: ExampleHooks {return configuration.exampleHooks }51    internal var suiteHooks: SuiteHooks { return configuration.suiteHooks }52    // MARK: Singleton Constructor53    private override init() {}54    static let sharedWorld = World()55    // MARK: Public Interface56    /**57        Exposes the World's Configuration object within the scope of the closure58        so that it may be configured. This method must not be called outside of59        an overridden +[QuickConfiguration configure:] method.60        - parameter closure:  A closure that takes a Configuration object that can61                         be mutated to change Quick's behavior.62    */63    internal func configure(_ closure: QuickConfigurer) {64        assert(!isConfigurationFinalized,65               "Quick cannot be configured outside of a +[QuickConfiguration configure:] method. You should not call -[World configure:] directly. Instead, subclass QuickConfiguration and override the +[QuickConfiguration configure:] method.")66        closure(configuration)67    }68    /**69        Finalizes the World's configuration.70        Any subsequent calls to World.configure() will raise.71    */72    internal func finalizeConfiguration() {73        isConfigurationFinalized = true74    }75    /**76        Returns an internally constructed root example group for the given77        QuickSpec class.78        A root example group with the description "root example group" is lazily79        initialized for each QuickSpec class. This root example group wraps the80        top level of a -[QuickSpec spec] method--it's thanks to this group that81        users can define beforeEach and it closures at the top level, like so:82            override func spec() {83                // These belong to the root example group84                beforeEach {}85                it("is at the top level") {}86            }87        - parameter cls: The QuickSpec class for which to retrieve the root example group.88        - returns: The root example group for the class.89    */90    internal func rootExampleGroupForSpecClass(_ cls: AnyClass) -> ExampleGroup {91        let name = String(describing: cls)92        if let group = specs[name] {93            return group94        } else {95            let group = ExampleGroup(96                description: "root example group",97                flags: [:],98                isInternalRootExampleGroup: true99            )100            specs[name] = group101            return group102        }103    }104    /**105        Returns all examples that should be run for a given spec class.106        There are two filtering passes that occur when determining which examples should be run.107        That is, these examples are the ones that are included by inclusion filters, and are108        not excluded by exclusion filters.109        - parameter specClass: The QuickSpec subclass for which examples are to be returned.110        - returns: A list of examples to be run as test invocations.111    */112    internal func examples(_ specClass: AnyClass) -> [Example] {113        // 1. Grab all included examples.114        let included = includedExamples115        // 2. Grab the intersection of (a) examples for this spec, and (b) included examples.116        let spec = rootExampleGroupForSpecClass(specClass).examples.filter { included.contains($0) }117        // 3. Remove all excluded examples.118        return spec.filter { example in119            !self.configuration.exclusionFilters.reduce(false) { $0 || $1(example) }120        }121    }122#if _runtime(_ObjC)123    @objc(examplesForSpecClass:)124    private func objc_examples(_ specClass: AnyClass) -> [Example] {125        return examples(specClass)126    }127#endif128    // MARK: Internal129    internal func registerSharedExample(_ name: String, closure: @escaping SharedExampleClosure) {130        raiseIfSharedExampleAlreadyRegistered(name)131        sharedExamples[name] = closure132    }133    internal func sharedExample(_ name: String) -> SharedExampleClosure {134        raiseIfSharedExampleNotRegistered(name)135        return sharedExamples[name]!136    }137    internal var includedExampleCount: Int {138        return includedExamples.count139    }140    internal var beforesCurrentlyExecuting: Bool {141        let suiteBeforesExecuting = suiteHooks.phase == .beforesExecuting142        let exampleBeforesExecuting = exampleHooks.phase == .beforesExecuting143        var groupBeforesExecuting = false144        if let runningExampleGroup = currentExampleMetadata?.example.group {145            groupBeforesExecuting = runningExampleGroup.phase == .beforesExecuting146        }147        return suiteBeforesExecuting || exampleBeforesExecuting || groupBeforesExecuting148    }149    internal var aftersCurrentlyExecuting: Bool {150        let suiteAftersExecuting = suiteHooks.phase == .aftersExecuting151        let exampleAftersExecuting = exampleHooks.phase == .aftersExecuting152        var groupAftersExecuting = false153        if let runningExampleGroup = currentExampleMetadata?.example.group {154            groupAftersExecuting = runningExampleGroup.phase == .aftersExecuting155        }156        return suiteAftersExecuting || exampleAftersExecuting || groupAftersExecuting157    }158    internal func performWithCurrentExampleGroup(_ group: ExampleGroup, closure: () -> Void) {159        let previousExampleGroup = currentExampleGroup160        currentExampleGroup = group161        closure()162        currentExampleGroup = previousExampleGroup163    }164    private var allExamples: [Example] {165        var all: [Example] = []166        for (_, group) in specs {167            group.walkDownExamples { all.append($0) }168        }169        return all170    }171    private var includedExamples: [Example] {172        let all = allExamples173        let included = all.filter { example in174            return self.configuration.inclusionFilters.reduce(false) { $0 || $1(example) }175        }176        if included.isEmpty && configuration.runAllWhenEverythingFiltered {177            return all178        } else {179            return included180        }...

...43    func isSatisfied(_ item: Product) -> Bool44}45protocol Filter {46    associatedtype T47    func filter<Spec: Specification>(_ items:[T], _ spec: Spec) -> [T] where Spec.T == T48}49class BetterFilter: Filter {50    typealias T = Product51    func filter<Spec: Specification>(_ items: [Product], _ spec: Spec) -> [Product] {52        var result = [Product]()53        for item in items {54            if spec.isSatisfied(item) {55                result.append(item)56            }57        }58        return result59    }60}61class ColorSpecification: Specification {62    typealias T = Product63    64    let color: Color65    66    init(_ color: Color) {67        self.color = color68    }69    70    func isSatisfied(_ item: Product) -> Bool {71        return item.color == color72    }73}74class SizeSpecification: Specification {75    typealias T = Product76    77    let size: Size78    79    init(_ size: Size) {80        self.size = size81    }82    83    func isSatisfied(_ item: Product) -> Bool {84        return item.size == size85    }86}87class AndSpecification<SpecA: Specification, SpecB: Specification, T>: Specification where SpecA.T == SpecB.T, SpecA.T == T88{89    typealias T = Product90    91    let specA: SpecA92    let specB: SpecB93    94    init(_ specA: SpecA, _ specB: SpecB) {95        self.specA = specA96        self.specB = specB97    }98    99    func isSatisfied(_ item: Product) -> Bool {100        return specA.isSatisfied(item) && specB.isSatisfied(item)101    }102}103print("============Better Filter ==============")104let betterFilter = BetterFilter()105for product in betterFilter.filter(products, ColorSpecification(.green)) {106    print(" - \(product.name) is \(product.color) and \(product.size)")107}108for product in betterFilter.filter(products, SizeSpecification(.large)) {109    print(" - \(product.name) is \(product.color) and \(product.size)")110}111print("========================================")112for product in betterFilter.filter(products,113                                   AndSpecification(ColorSpecification(.blue),114                                                    SizeSpecification(.large))) {...

1class A{2    init(a: Int){3    }4}5class B: A{6    init(a: Int, b: Int){7        super.init(a: a)8    }9}10class C: B{11    init(a: Int, b: Int, c: Int){12        super.init(a: a, b: b)13    }14}15let c = C(a: 1, b: 2, c: 3)16let b = B(a: 1, b: 2)17let a = A(a: 1)18if let _ = c as? B{19    print("c is B")20}21if let _ = c as? A{22    print("c is A")23}24if let _ = b as? A{25    print("b is A")26}27if let _ = a as? A{28    print("a is A")29}30class A{31    init(a: Int){32    }33}34class B: A{35    init(a: Int, b: Int){36        super.init(a: a)37    }38}39class C: B{40    init(a: Int, b: Int, c: Int){41        super.init(a: a, b: b)42    }43}44let c = C(a: 1, b: 2, c: 3)45let b = B(a: 1, b: 2)46let a = A(a: 1)47if c is B{48    print("c is B")49}50if c is A{51    print("c is A")52}53if b is A{54    print("b is A")55}56if a is A{57    print("a is A")58}59protocol P{60    var p: Int {get}61}62class A: P{63    init(p: Int){64    }65}66class B: A{67    init(p

1import Foundation2class Person {3    init(name: String) {4    }5}6extension Person {7    static func isPerson(obj: AnyObject) -> Bool {8    }9}10let p = Person(name: "John")11Person.isPerson(obj: obj)12import Foundation13class Person {14    init(name: String) {15    }16}17extension Person {18    static func isPerson(obj: AnyObject) -> Bool {19    }20}21let p = Person(name: "John")22Person.isPerson(obj: obj)23import Foundation24class Person {25    init(name: String) {26    }27}28extension Person {29    static func isPerson(obj: AnyObject) -> Bool {30    }31}32let p = Person(name: "John")33Person.isPerson(obj: obj)34import Foundation35class Person {36    init(name: String) {37    }38}39extension Person {40    static func isPerson(obj: AnyObject) -> Bool {41    }42}43let p = Person(name: "John")44Person.isPerson(obj: obj)45import Foundation46class Person {47    init(name: String) {48    }49}50extension Person {51    static func isPerson(obj: AnyObject) -> Bool {52    }53}54let p = Person(name: "John")55Person.isPerson(obj: obj)56import Foundation57class Person {58    init(name: String) {59    }60}61extension Person {62    static func isPerson(obj:

1class Person {2    init(name: String) {3    }4    func spec() {5        print("I am a person")6    }7}8class Student: Person {9    init(name: String, id: Int) {10        super.init(name: name)11    }12    override func spec() {13        print("I am a student")14    }15}16var p = Person(name: "Sachin")17p.spec()18var s = Student(name: "Rahul", id: 1)19s.spec()20class Person {21    init(name: String) {22    }23    func spec() {24        print("I am a person")25    }26}27class Student: Person {28    init(name: String, id: Int) {29        super.init(name: name)30    }31    override func spec() {32        print("I am a student")33    }34}35var p: Person = Person(name: "Sachin")36p.spec()37var s: Person = Student(name: "Rahul", id: 1)38s.spec()39class Person {40    init(name: String) {41    }42    func spec() {43        print("I am a person")44    }45}46class Student: Person {47    init(name: String, id: Int) {48        super.init(name: name)49    }50    override func spec() {51        print("I am a student")52    }53}54var p: Person = Person(name: "Sachin")55p.spec()56var s: Student = Student(name: "Rahul", id: 1)57s.spec()58class Person {59    init(name: String) {60    }61    func spec() {62        print("I am a person")63    }64}65class Student: Person {66    init(name: String, id

1import UIKit2class ViewController: UIViewController {3    override func viewDidLoad() {4        super.viewDidLoad()5        let p = Person()6        p.eat()7    }8}9class Person {10    func eat(){11        print("eating")12    }13}14import UIKit15class ViewController: UIViewController {16    override func viewDidLoad() {17        super.viewDidLoad()18        let p = Person()19        p.eat()20    }21}22class Person {23    func eat(){24        print("eating")25    }26}27import UIKit28class ViewController: UIViewController {29    override func viewDidLoad() {30        super.viewDidLoad()31        let p = Person()32        p.eat()33    }34}35class Person {36    func eat(){37        print("eating")38    }39}40import UIKit41class ViewController: UIViewController {42    override func viewDidLoad() {43        super.viewDidLoad()44        let p = Person()45        p.eat()46    }47}48class Person {49    func eat(){50        print("eating")51    }52}53import UIKit54class ViewController: UIViewController {55    override func viewDidLoad() {56        super.viewDidLoad()57        let p = Person()58        p.eat()59    }60}61class Person {62    func eat(){63        print("eating")64    }65}66import UIKit67class ViewController: UIViewController {68    override func viewDidLoad() {69        super.viewDidLoad()70        let p = Person()71        p.eat()72    }73}74class Person {75    func eat(){76        print("eating")77    }78}79import UIKit80class ViewController: UIViewController {81    override func viewDidLoad() {82        super.viewDidLoad()83        let p = Person()84        p.eat()85    }86}87class Person {

1class Person {2    init(name: String) {3    }4}5let person = Person(name: "John")6if person is Person {7    print("This is a person")8}9class Person {10    init(name: String) {11    }12}13let person = Person(name: "John")14if person is Person {15    print("This is a person")16}17class Person {18    init(name: String) {19    }20}21let person = Person(name: "John")22if person is Person {23    print("This is a person")24}25class Person {26    init(name: String) {27    }28}29let person = Person(name: "John")30if person is Person {31    print("This is a person")32}33class Person {34    init(name: String) {35    }36}37let person = Person(name: "John")38if person is Person {39    print("This is a person")40}41class Person {42    init(name: String) {43    }44}45let person = Person(name: "John")46if person is Person {47    print("This is a person")48}49class Person {50    init(name: String) {51    }52}53let person = Person(name: "John")54if person is Person {55    print("This is a person")56}57class Person {58    init(name: String) {59    }60}

1import Foundation2import UIKit3class ViewController: UIViewController {4    override func viewDidLoad() {5        super.viewDidLoad()6        let person = Person()

1import Foundation2class A {3}4class B: A {5}6func isClass<T>(_ a: T) -> Bool {7    return (a as AnyObject) is A8}9let a = A()10let b = B()11import Foundation12class A {13}14class B: A {15}16func isClass<T>(_ a: T) -> Bool {17    return (a as AnyObject) is B18}19let a = A()20let b = B()21import Foundation22class A {23}24class B: A {25}26func isClass<T>(_ a: T) -> Bool {27    return (a as? A) != nil28}29let a = A()30let b = B()31import Foundation32class A {33}34class B: A {35}36func isClass<T>(_ a: T) -> Bool {37    return (a as? B) != nil38}39let a = A()40let b = B()41import Foundation42class A {43}44class B: A {45}46func isClass<T>(_ a: T) -> Bool {47    return (a as? B) == nil48}49let a = A()50let b = B()51import Foundation52class A {