Classes

A class groups data with the methods that work on it. Define one inside a script or in a .bx file, then create an instance with new.

Constructor, this and variables

init() initializes the object. Use this for public fields and variables for private instance state. Returning this also makes methods chainable.

class Counter {
    function init( start = 0 ) {
        variables.count = start;
        return this;
    }

    function increment() {
        variables.count += 1;
        return this;
    }

    function get() {
        return variables.count;
    }
}

println( new Counter( 5 ).increment().increment().get() );

7

File-based classes

Put a class in a file such as models/Pet.bx:

class {
    function init( name ) {
        this.name = name;
        return this;
    }

    function speak() {
        return "I am " & this.name;
    }
}

Import and use it from your application:

import models.Pet;
println( new Pet( "Rex" ).speak() );

File-based classes need a project filesystem; use inline classes in the browser playground.

Inheritance and interfaces

Use extends="Parent" to inherit behavior and implements="Interface" to declare an interface. A child can override methods and call the parent implementation with super.method().

class Animal {
    function speak() {
        return "hello";
    }
}

class Dog extends="Animal" {
    function speak() {
        return super.speak() & " from Dog";
    }
}

println( new Dog().speak() );

hello from Dog

Properties and accessors

Properties provide getter and setter methods:

class Person accessors="true" {
    property name;
}

person = new Person();
person.setName( "Ann" );
println( person.getName() );

Ann

For a guided introduction, see the classes lesson.