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29. Swift – Type Casting


To validate the type of an instance 'Type Casting' comes into play in Swift language. It is used to check whether the instance type belongs to a particular super class or subclass or it is defined in its own hierarchy. Swift type casting provides two operators 'is' to check the type of a value and 'as' and to cast the type value to a different type. Type casting also checks whether the instance type follows particular protocol conformance standard.

Defining a Class Hierarchy Type casting is used to check the type of instances to find out whether it belongs to particular class type. Also, it checks hierarchy of classes and its subclasses to check and cast those instances to make it as a same hierarchy. class Subjects { var physics: String init(physics: String) { self.physics = physics } }

class Chemistry: Subjects { var equations: String init(physics: String, equations: String) { self.equations = equations super.init(physics: physics) } }

class Maths: Subjects { var formulae: String init(physics: String, formulae: String) { self.formulae = formulae super.init(physics: physics) } } 181

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