Object-Oriented Programming

This guide introduces the OOP model used in Eiger, including Classes and Dataclasses.

Classes

A class defines a blueprint for objects. It can contain properties and functions (methods), and it supports constructors for initializing instances.

Syntax

class ClassName
    let [modifiers] propertyName

    ~ The `new` function acts as a constructor.
    func new(parameters)
        ~ `this` is a reference to the current class instance.
        this.propertyName = parameter
    end
end

Example

class Person
    let private m_name
    let private m_age
    let private m_birthYear

    ~ Constructor
    func new(name, age, birthYear)
        this.m_name = name
        this.m_age = age
        this.m_birthYear = birthYear
    end

    ~ Method
    func summary()
        ret (m_name + " (" + m_age.asString + " years old, born " + m_birthYear.asString + ")")
    end
end

~ Creating a class instance from a "blueprint" (class)
let personOne = Person("John", 25, 2000)

~ Calling the summary method in personOne
emitln(personOne.summary())

Features

• Properties are declared with let, just like variables
• Access Modifiers:
  • public (default): Accessible from anywhere
  • private: Accessible only within the class
• Constructor:
  • Declared with func new(params)
  • Used to initialize the object

Dataclasses

A dataclass defines a group of static properties. It behaves like a class but does not have a constructor.

Syntax

dataclass ClassName
    let [modifiers] propertyName = value

    func method(params)
        ~ ...
    end
end

Example

dataclass math
    ~ Mathematical Constants
    let readonly pi = 3.14159265358979323846
    let readonly e = 2.718281828459045

    ~ get the unsigned value of a number
    func abs(n)
        if n < 0 then
            ret -n
        else
            ret n
        end
    end

    func sin(theta)
        ~ ...
    end
end

emitln(math.abs(-128))
emitln(math.sin(math.pi))

Features

• Static by nature: You do not instantiate a dataclass.
• Access Modifiers:
  • public (default): Accessible from anywhere
  • private: Accessible only within the dataclass
• new function is not used.