LESSON 183 OF 348 · OBJECT-ORIENTED PROGRAMMING

Class Fields in Scala in Scala

Lesson

TL ; DR:

A field is a variable that lives inside a class. Each object of that class has its own copy.
Declare a field with a type and a name, with public in front so other code can read and write it:
```
class Dog {
    public var name: String = ""
    public var age: Int = 0
}
```
Access a field on an object with the dot operator: dog.name = "Rex"

Full lesson:

Right now your Dog class is just an empty shell — every Dog object you create is identical to every other one. We need a way to attach data to each object.

That's what fields are for. A field is a variable that belongs to a class — and each object created from that class gets its own copy of every field.

Declaring fields

class Dog {
    public var name: String = ""
    public var age: Int = 0
}

public means "any code can read and write this field". You'll see private later for fields that should only be touched by the class itself.
var name: String = "" is just a variable declaration — same syntax you'd use anywhere else.

Reading and writing fields

Dog dog = new Dog()
dog.name = "Rex"        // write
dog.age = 4
println(dog.name)   // read → prints "Rex"

Each object has its own slot for every field, so two dogs can have different names without interfering.

Default values

If you don't assign a field, Scala fills it in for you:

Numbers default to 0
Boolean defaults to false
References (String, arrays, other classes) default to null

Your task

Update the Dog class to have two fields: name (a String) and age (an Int). Then in mainFunction, set them on the dog object so the pre-filled println prints:

Rex is 4 years old

STEP 1 OF 2

Guided

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