Instances

Instances are objects created from a class definition. Each instance has its own copy of the class members.

Creating Instances

There are three ways to create an instance:

class "Player" {
    name = "Unknown";
}

-- All three are equivalent:
local p1 = Player.new()
local p2 = Player:new()
local p3 = Player()

All three methods accept constructor arguments:

class "Player" {
    name = "";

    __construct = function(self, n)
        self.name = n
    end;
}

local p1 = Player.new("Alice")
local p2 = Player:new("Bob")
local p3 = Player("Charlie")

Class vs Instance

A class is the template. An instance is a copy of that template with its own data.

class "Counter" {
    value = 0;
}

-- Counter is the class
print(Counter)  -- SimplooObject: Counter <class>

-- These are instances
local a = Counter.new()
local b = Counter.new()

print(a)  -- SimplooObject: Counter <instance>
print(b)  -- SimplooObject: Counter <instance>

-- Each instance has its own data
a.value = 10
print(a.value)  -- 10
print(b.value)  -- 0 (unchanged)

Class Reference

Every instance can access its class via get_class():

local player = Player.new()

print(player:get_class() == Player)  -- true
print(player:get_name())             -- Player

Instance Identity

Each call to .new() creates a separate instance:

local a = Player.new()
local b = Player.new()
local c = a  -- c references the same instance as a

print(a == b)  -- false (different instances)
print(a == c)  -- true (same instance)

Built-in Instance Methods

Every instance has these methods available:

get_name()

Returns the class name as a string:

local player = Player.new()
print(player:get_name())  -- Player

get_class()

Returns the class:

local player = Player.new()
print(player:get_class() == Player)  -- true

instance_of(other)

Checks if the instance is derived from another class (useful with inheritance):

class "Animal" {}
class "Dog" extends "Animal" {}

local dog = Dog.new()
print(dog:instance_of(Animal))  -- true
print(dog:instance_of(Dog))     -- true

See Instance Methods Reference for more details.

Passing Instances Around

Instances can be passed to functions, stored in tables, and used like any Lua value:

class "Player" {
    name = "";
    health = 100;

    __construct = function(self, n)
        self.name = n
    end;
}

-- Store in a table
local players = {}
table.insert(players, Player.new("Alice"))
table.insert(players, Player.new("Bob"))

-- Pass to a function
local function damage(player, amount)
    player.health = player.health - amount
end

damage(players[1], 25)
print(players[1].health)  -- 75

Complete Example

Block SyntaxBuilder Syntax

dofile("simploo.lua")

class "Enemy" {
    name = "Unknown";
    health = 50;
    damage = 10;

    __construct = function(self, name, hp, dmg)
        self.name = name
        self.health = hp or 50
        self.damage = dmg or 10
    end;

    attack = function(self, target)
        print(self.name .. " attacks " .. target.name .. " for " .. self.damage .. " damage!")
        target.health = target.health - self.damage
    end;

    isAlive = function(self)
        return self.health > 0
    end;
}

-- Create multiple instances
local goblin = Enemy.new("Goblin", 30, 5)
local orc = Enemy.new("Orc", 100, 20)
local dragon = Enemy("Dragon", 500, 50)

-- Each has its own state
print(goblin.health)  -- 30
print(orc.health)     -- 100
print(dragon.health)  -- 500

-- Instances interact
dragon:attack(goblin)  -- Dragon attacks Goblin for 50 damage!
print(goblin:isAlive())  -- false

dofile("simploo.lua")

local enemy = class("Enemy")
enemy.name = "Unknown"
enemy.health = 50
enemy.damage = 10

function enemy:__construct(name, hp, dmg)
    self.name = name
    self.health = hp or 50
    self.damage = dmg or 10
end

function enemy:attack(target)
    print(self.name .. " attacks " .. target.name .. " for " .. self.damage .. " damage!")
    target.health = target.health - self.damage
end

function enemy:isAlive()
    return self.health > 0
end

enemy:register()

-- Create multiple instances
local goblin = Enemy.new("Goblin", 30, 5)
local orc = Enemy.new("Orc", 100, 20)
local dragon = Enemy("Dragon", 500, 50)

-- Each has its own state
print(goblin.health)  -- 30
print(orc.health)     -- 100
print(dragon.health)  -- 500

-- Instances interact
dragon:attack(goblin)  -- Dragon attacks Goblin for 50 damage!
print(goblin:isAlive())  -- false