Object Oriented Programming
Object oriented programming is supported through inheritance and methods, which are virtual procedures. Methods work in the same way as procs, including UFCS, but the runtime type of the object that a method is called with is used to determine which version to call.
Inheritance is created with the
of keyword in the type declaration of an object. A method is overridden by creating a new method with parameter types of the subtype.
type Animal = ref object of RootObj name: string age: int method vocalize(this: Animal): string = "..." method ageHumanYrs(this: Animal): int = this.age type Dog = ref object of Animal method vocalize(this: Dog): string = "woof" method ageHumanYrs(this: Dog): int = this.age * 7 type Cat = ref object of Animal method vocalize(this: Cat): string = "meow" var animals: seq[Animal] = @ animals.add(Dog(name: "Sparky", age: 10)) animals.add(Cat(name: "Mitten", age: 10)) for a in animals: echo a.vocalize() echo a.ageHumanYrs()
$ nim c -r oop.nim woof 70 meow 10
It is also possible to check if an object is of a given subtype with the
of keyword. For example,
echo(animals of Dog) echo(animals of Cat) echo(animals of Animal)
$ nim c -r of_op.nim true false true