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Kotlin Type Checking and Smart Cast with Examples

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  Type Checking in Kotlin For certain scenarios, we need to check the type of the object i.e. we need to identify the class of the object before executing any function on that object. Consider a scenario where you have different types of objects in an array. You are looping on that array and executing some functionality. If you call a method that does not exist in the object, an error will be thrown at the runtime. To prevent such errors, we do type checking. In Kotlin, we have an  " is operator"  that helps in checking the type of the object. fun main() { var p1 = Person() if(p1 is Person) // Use of is operator { p1.sayHi() } } class Person{ fun sayHi() = println("Hi") } Explanation -  Here, we are checking the type of p1 instance that if it is of type Person - call its sayHi() method. In this case, it is evident that the object is of type Person only but for scenarios where we need to check the type - we use an "is operator"....
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Kotlin Interfaces With Example

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We can group classes based on what they are i.e. based on inheritance. The circle is a shape, Square is a shape - these classes belong to the Shape hierarchy because they are Shapes. We can also group classes based on what they do or what behavior they exhibit. A circle object can be dragged, a person object can be dragged - here we have grouped classes Circle and Person based on the behavior dragging . Even if the classes do not belong to a single class hierarchy, we can group them based on the behavior. This is where Interfaces come into the picture. Interface -  When you want your class to exhibit certain behavior irrespective of the class hierarchy they belong to - Use Interface. Interfaces help you to implement polymorphism based on the behavior defined in the interface. Methods defined in the interfaces are 100% abstract but in Kotlin you can also define methods that are non-abstract i.e. methods can have a body. Non-abstract methods in interfaces do not have any state they c...
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Polymorphism in Kotlin With Example

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Polymorphism is one of the most important topics in Object-Oriented Programming. It goes hand in hand with Inheritance . Poly means many and morph means forms i.e. the same method behaves differently based on the object. Here we have different forms of the method that exhibits different behavior based on the object. To define Polymorphism in simple words - A parent can hold a reference to its child and can call methods which are provided by the parent class. Let's understand this with an example -  fun main() { val circle : Shape = Circle(4.0) val square : Shape = Square(4.0) } open class Shape{ open fun area() :Double{ return 0.0 } } class Circle(val radius:Double) : Shape(){ override fun area(): Double { return Math.PI * radius * radius } } class Square(val side:Double) : Shape(){ override fun area(): Double { return side * side } } Explanation -   Here we have defined a Shape class which is a base class and open ...
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