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354 lines
9.1 KiB
ReStructuredText
354 lines
9.1 KiB
ReStructuredText
hump.class
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==========
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::
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Class = require "hump.class"
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A small, fast class/prototype implementation with multiple inheritance.
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Implements `class commons <https://github.com/bartbes/Class-Commons>`_.
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**Example**::
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Critter = Class{
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init = function(self, pos, img)
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self.pos = pos
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self.img = img
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end,
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speed = 5
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}
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function Critter:update(dt, player)
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-- see hump.vector
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local dir = (player.pos - self.pos):normalize_inplace()
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self.pos = self.pos + dir * Critter.speed * dt
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end
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function Critter:draw()
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love.graphics.draw(self.img, self.pos.x, self.pos.y)
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end
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List of Functions
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-----------------
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* :func:`Class.new() <Class.new>`
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* :func:`class.init(object, ...) <class.init>`
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* :func:`Class:include(other) <Class:include>`
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* :func:`class:clone() <class:clone>`
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Function Reference
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------------------
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.. function:: Class.new()
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Class.new({init = constructor, __includes = parents, ...})
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:param function constructor: Class constructor. Can be accessed with ``theclass.init(object, ...)``. (optional)
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:param class or table of classes parents: Classes to inherit from. Can either be a single class or a table of classes. (optional)
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:param mixed ...: Any other fields or methods common to all instances of this class. (optional)
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:returns: The class.
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Declare a new class.
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``init()`` will receive the new object instance as first argument. Any other
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arguments will also be forwarded (see examples), i.e. ``init()`` has the
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following signature::
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function init(self, ...)
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If you do not specify a constructor, an empty constructor will be used instead.
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The name of the variable that holds the module can be used as a shortcut to
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``new()`` (see example).
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**Examples**::
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Class = require 'hump.class' -- `Class' is now a shortcut to new()
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-- define a class class
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Feline = Class{
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init = function(self, size, weight)
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self.size = size
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self.weight = weight
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end;
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-- define a method
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stats = function(self)
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return string.format("size: %.02f, weight: %.02f", self.size, self.weight)
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end;
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}
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-- create two objects
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garfield = Feline(.7, 45)
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felix = Feline(.8, 12)
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print("Garfield: " .. garfield:stats(), "Felix: " .. felix:stats())
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::
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Class = require 'hump.class'
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-- same as above, but with 'external' function definitions
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Feline = Class{}
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function Feline:init(size, weight)
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self.size = size
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self.weight = weight
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end
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function Feline:stats()
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return string.format("size: %.02f, weight: %.02f", self.size, self.weight)
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end
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garfield = Feline(.7, 45)
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print(Feline, garfield)
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::
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Class = require 'hump.class'
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A = Class{
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foo = function() print('foo') end
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}
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B = Class{
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bar = function() print('bar') end
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}
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-- single inheritance
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C = Class{__includes = A}
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instance = C()
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instance:foo() -- prints 'foo'
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instance:bar() -- error: function not defined
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-- multiple inheritance
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D = Class{__includes = {A,B}}
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instance = D()
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instance:foo() -- prints 'foo'
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instance:bar() -- prints 'bar'
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::
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-- class attributes are shared across instances
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A = Class{ foo = 'foo' } -- foo is a class attribute/static member
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one, two, three = A(), A(), A()
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print(one.foo, two.foo, three.foo) --> prints 'foo foo foo'
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one.foo = 'bar' -- overwrite/specify for instance `one' only
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print(one.foo, two.foo, three.foo) --> prints 'bar foo foo'
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A.foo = 'baz' -- overwrite for all instances without specification
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print(one.foo, two.foo, three.foo) --> prints 'bar baz baz'
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.. function:: class.init(object, ...)
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:param Object object: The object. Usually ``self``.
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:param mixed ...: Arguments to pass to the constructor.
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:returns: Whatever the parent class constructor returns.
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Calls class constructor of a class on an object.
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Derived classes should use this function their constructors to initialize the
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parent class(es) portions of the object.
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**Example**::
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Class = require 'hump.class'
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Shape = Class{
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init = function(self, area)
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self.area = area
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end;
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__tostring = function(self)
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return "area = " .. self.area
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end
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}
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Rectangle = Class{__includes = Shape,
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init = function(self, width, height)
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Shape.init(self, width * height)
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self.width = width
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self.height = height
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end;
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__tostring = function(self)
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local strs = {
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"width = " .. self.width,
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"height = " .. self.height,
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Shape.__tostring(self)
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}
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return table.concat(strs, ", ")
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end
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}
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print( Rectangle(2,4) ) -- prints 'width = 2, height = 4, area = 8'
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.. function:: Class:include(other)
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:param tables other: Parent classes/mixins.
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:returns: The class.
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Inherit functions and variables of another class, but only if they are not
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already defined. This is done by (deeply) copying the functions and variables
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over to the subclass.
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.. note::
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``class:include()`` doesn't actually care if the arguments supplied are
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hump classes. Just any table will work.
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.. note::
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You can use ``Class.include(a, b)`` to copy any fields from table ``a``
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to table ``b`` (see second example).
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**Examples**::
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Class = require 'hump.class'
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Entity = Class{
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init = function(self)
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GameObjects.register(self)
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end
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}
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Collidable = {
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dispatch_collision = function(self, other, dx, dy)
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if self.collision_handler[other.type])
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return collision_handler[other.type](self, other, dx, dy)
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end
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return collision_handler["*"](self, other, dx, dy)
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end,
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collision_handler = {["*"] = function() end},
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}
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Spaceship = Class{
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init = function(self)
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self.type = "Spaceship"
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-- ...
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end
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}
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-- make Spaceship collidable
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Spaceship:include(Collidable)
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Spaceship.collision_handler["Spaceship"] = function(self, other, dx, dy)
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-- ...
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end
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::
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-- using Class.include()
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Class = require 'hump.class'
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a = {
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foo = 'bar',
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bar = {one = 1, two = 2, three = 3},
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baz = function() print('baz') end,
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}
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b = {
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foo = 'nothing to see here...'
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}
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Class.include(b, a) -- copy values from a to b
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-- note that neither a nor b are hump classes!
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print(a.foo, b.foo) -- prints 'bar nothing to see here...'
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b.baz() -- prints 'baz'
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b.bar.one = 10 -- changes only values in b
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print(a.bar.one, b.bar.one) -- prints '1 10'
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.. function:: class:clone()
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:returns: A deep copy of the class/table.
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Create a clone/deep copy of the class.
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.. note::
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You can use ``Class.clone(a)`` to create a deep copy of any table (see
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second example).
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**Examples**::
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Class = require 'hump.class'
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point = Class{ x = 0, y = 0 }
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a = point:clone()
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a.x, a.y = 10, 10
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print(a.x, a.y) --> prints '10 10'
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b = point:clone()
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print(b.x, b.y) --> prints '0 0'
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c = a:clone()
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print(c.x, c.y) --> prints '10 10'
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::
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-- using Class.clone() to copy tables
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Class = require 'hump.class'
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a = {
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foo = 'bar',
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bar = {one = 1, two = 2, three = 3},
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baz = function() print('baz') end,
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}
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b = Class.clone(a)
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b.baz() -- prints 'baz'
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b.bar.one = 10
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print(a.bar.one, b.bar.one) -- prints '1 10'
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Caveats
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-------
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Be careful when using metamethods like ``__add`` or ``__mul``: If a subclass
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inherits those methods from a superclass, but does not overwrite them, the
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result of the operation may be of the type superclass. Consider the following::
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Class = require 'hump.class'
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A = Class{init = function(self, x) self.x = x end}
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function A:__add(other) return A(self.x + other.x) end
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function A:show() print("A:", self.x) end
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B = Class{init = function(self, x, y) A.init(self, x) self.y = y end}
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function B:show() print("B:", self.x, self.y) end
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function B:foo() print("foo") end
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B:include(A)
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one, two = B(1,2), B(3,4)
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result = one + two -- result will be of type A, *not* B!
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result:show() -- prints "A: 4"
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result:foo() -- error: method does not exist
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Note that while you can define the ``__index`` metamethod of the class, this is
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not a good idea: It will break the class mechanism. To add a custom ``__index``
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metamethod without breaking the class system, you have to use ``rawget()``. But
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beware that this won't affect subclasses::
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Class = require 'hump.class'
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A = Class{}
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function A:foo() print('bar') end
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function A:__index(key)
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print(key)
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return rawget(A, key)
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end
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instance = A()
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instance:foo() -- prints foo bar
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B = Class{__includes = A}
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instance = B()
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instance:foo() -- prints only foo
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