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let sa = [ Chemistry(physics: "solid physics", equations: "Hertz"), Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")]

let samplechem = Chemistry(physics: "solid physics", equations: "Hertz") println("Instance physics is: \(samplechem.physics)") println("Instance equation is: \(samplechem.equations)")

let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz") println("Instance physics is: \(samplemaths.physics)") println("Instance formulae is: \(samplemaths.formulae)") When we run the above program using playground, we get the following result: Instance physics is: solid physics Instance equation is: Hertz Instance physics is: Fluid Dynamics Instance formulae is: Giga Hertz

Type Checking Type checking is done with the 'is' operator. The 'is' type check operator checks whether the instance belongs to particular subclass type and returns 'true' if it belongs to that instance else it will return 'false'. class Subjects { var physics: String init(physics: String) { self.physics = physics } }

class Chemistry: Subjects { var equations: String init(physics: String, equations: String) { 182

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