scala • classes • objects • singleton

Classes and Objects

Like in java and .net a class is a blue print for objects. Once we define class, we can create multiple objects from the class with the keyword new.

class Product {
    // class definition goes here
}
//creating an object
new Product

Fields

class Product {
    var price = 0 //Field
}
val soap = new Product
val chair = new Product

since field is var type after creating the object we can reassign with a different value to the field.

soap.price = 30

The image of the objects in memory might look like:Figure 1

image
Figure 1 - Memory allocation

It’s obvious; soap object cannot be reinitialized because the objects given that they are vals, not vars.

// Won’t compile, because soap is a val
 soap = new Product

“public” in Java, you simply say nothing in Scala

class Product {
    private var price = 0
    def add(b: Int): Unit = {
      price += b
}
}

”semicolon” at the end of a statement is usually optional

var hello = “hello scala without semicolon”

But, a semicolon is required if you write multiple statements on a single line:

var hello = “hello scala with semicolon”; println(hello)

Singleton Object

Scala is more unique and easy to use language than java.

Scala cannot have static members

Scala has an easy way to define singleton object. Like we defining a class in scala we can easily define an object.

Instead of the keyword “class” we use the keyword “object”

object Product {
    private var price = 0
    def add(b: Int): Unit = {
      price += b
}
}

Hope you understood about classes and objects in scala. Next we will look into functional objects and methods.

Blog Series