Demonstrating Case Classes in Scala
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This document discusses modeling products and categories in Scala using case classes. It describes the attributes of products (name, category, optional description) and categories (name, optional parent category). It shows how to define regular classes in Java and Scala to represent these, but notes that Scala case classes provide additional benefits out of the box, such as a companion object with factory methods, automatic fields from class parameters, nicer toString output, and attribute-based equality. It cautions that case classes have bytecode overhead and generated code that could clutter interfaces.
![And
in
Scala?
class Category(
val name: String,
val parent: Option[Category])
class Product(
val name: String,
val description: String,
val category: Category)](https://image.slidesharecdn.com/scala-caseclasses-140603143407-phpapp01/85/Demonstrating-Case-Classes-in-Scala-5-320.jpg)
![Or
even
be>er,
case class Category(
name: String,
parent: Option[Category])
case class Product(
name: String,
description: String,
category: Category)](https://image.slidesharecdn.com/scala-caseclasses-140603143407-phpapp01/85/Demonstrating-Case-Classes-in-Scala-6-320.jpg)
Demonstrating Case Classes in Scala
- 2. Let's model the following • A product has a name, category and an op;onal descrip;on • A category has a name and may have a parent category • All the above a>ributes are read-‐only
- 3. public class Category { private String name; private Category parent; public Category(String name, Category parent) { this.name = name; this.parent = parent; } public String getName() { return name; } public Category getParent() { return parent; } }
- 4. public class Product { private String name; private String description; private Category category; // TODO: What am I missing? public Product(String name, String description, Category category) { this.name = name; this.description = description; this.category = category; } public String getName() { return name; } public String getDescription() { return description; } public Category getCategory() { return category; } }
- 5. And in Scala? class Category( val name: String, val parent: Option[Category]) class Product( val name: String, val description: String, val category: Category)
- 6. Or even be>er, case class Category( name: String, parent: Option[Category]) case class Product( name: String, description: String, category: Category)
- 7. What you get for free • Companion object with factory-‐like apply methods • Class parameters become fields • Nicer toString • A>ribute based equality • Pa>ern matching • Copy method to 'clone' instances
- 8. Be mindful of • Bytecode overhead • Generated code might clu>er your interface • Case class inheritance