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Case Classes
Case Classes are a syntactic sugar that allows you to save a lot of boilerplate code. Consider the following Java class:
class Book
{
String name;
String author;
final int id;
public Book(String name, String author, int id)
{
this.name = name;
this.author = author;
this.id = id;
}
Simple enough, though you may also need an
equals, hashCode and toString implementation. public String toString()
{
return "Book(" + this.name + ", " + this.author + ", " + this.id + ")";
}
public boolean equals(Object other)
{
if (!(obj instanceof Book)) return false;
final Book otherBook = (Book) other;
if (this.name != otherBook.name || this.name == null || !this.name.equals(otherBook.name)
return false;
if (this.author != otherBook.author || this.author == null || !this.author.equals(otherBook.author)
return false;
if (this.id != otherBook.id)
return false;
return true;
}
public int hashCode()
{
final int prime = 31;
int result = 1;
result = prime * result + (this.name == null ? 0 : this.name.hashCode());
result = prime * result + (this.author == null ? 0 : this.author.hashCode());
result = prime * result + this.id;
return result;
}
}
For a class as simple as the
Book class, this is a lot of boilerplate. Although IDEs might help you with this by generating the boilerplate code for you, maintaining it still costs a lot of time. In Dyvil, the compiler can generate all this code by using the case class modifier:case class Book(var name: String, var author: String, let id: int)
In addition to all methods in the Java class above, a Case Class generates a static
apply method that can be used to construct instances:// generated in the Book class:
static func apply(name: String, author: String, id: int) -> Book = new Book(name, author, id)
// usage:
let book = Book("The Dyvil Language Reference", "Dyvil Team", 0xCAFEBABE)
Case Classes provide extensive support for use in Pattern Matching by generating two different
unapply methods:// generated in the Book class:
static func unapply(value: any) -> (String, String, int)? = value is Book ? unapply(value as Book) : null
static func unapply(value: Book) -> (String, String, int) = (value.name, value.author, value.id)
// usage:
book match {
// match a book with any name, the author "Dyvil Team" and any id and store the name
case Book(var name, "Dyvil Team", _) => print name
}
Last modified 5yr ago