Joose.Cookbook.Basics.Recipe1 - The (always classic) Point example.
Class('Point', {
has : {
x : { is : 'rw', required : true },
y : { is : 'rw', required : true }
},
methods : {
clear : function () {
this.setX(0)
this.setY(0)
}
}
})
Class('Point3D', {
isa : Point,
has : {
z : { is : 'rw', required : true }
},
after : {
clear : function () {
this.setZ(0)
}
}
})
var point1 = new Point({ x : 5, y : 7})
var point3d = new Point3D({ x : 5, y : 7, z : -5})
When Joose is loaded, it exports a set of sugar functions into global namespace. This means that we import some functions which serve as Joose "keywords". These aren't real language keywords, they're just JavaScript functions exported into our package.
Joose automatically makes our class a subclass of "Joose.Meta.Object". This class provides us with a constructor that respects our attributes, as well other features.
Now, onto the keywords. The first one we see here is Class, which starts the declaration of the class.
Class accepts 1 or 2 arguments - optional class name and a object, describing a class. Each property of that
object is called builder.
Class converts given class name into constructor. If no class name were provided the anonymous class will be created.
Class returns a constructor of declared class.
The first builder we see is has, which defines the attributes in our class:
has : {
x : { is : 'rw', required : true },
y : { is : 'rw', required : true }
}
This will create attributes named x and y. The accessors, generated for this attributes will be read-write.
The required : true parameter means that this attribute must be provided when a new object is created.
A point object without coordinates doesn't make much sense, so we don't allow it.
We have defined our attributes; next we define our methods. In Joose, as with regular JavaScript, a method is just a function.
It should be defined in the methods builder:
methods : {
clear : function () {
this.setX(0)
this.setY(0)
}
}
That concludes the Point class.
Next we have a subclass of Point, Point3D. To declare our superclass, we use the isa builder:
isa : Point
Note, that Joose allows you to have only one superclass. As a cleaner alternative for multiple inheritance Joose provides Roles mechanism.
Next we create a new attribute for Point3D called z.
has : {
z : { is : 'rw', required : true }
},
This attribute is just like Point's x and y attributes.
The after builder demonstrates a Joose feature called "method modifiers" (or "advice" for the AOP inclined):
after : {
clear : function () {
this.setZ(0)
}
}
When clear is called on a Point3D object, our modifier method gets called as well. Unsurprisingly, the modifier is called after the real method.
In this case, the real clear method is inherited from Point. Our modifier method receives the same arguments as those passed to the modified method.
Of course, using the after modifier is not the only way to accomplish this. You can get the same results with this code:
methods : {
clear : function () {
this.SUPER()
this.setZ(0)
}
}
You could also use another Joose method modifier, override:
override : {
clear : function () {
this.SUPER()
this.setZ(0)
}
}
The override modifier allows you to use the this.SUPER call to dispatch to the superclass's method in a very Ruby-ish style.
The choice of whether to use a method modifier, and which one to use, is often a question of style as much as functionality.
Since Point inherits from [Joose.Meta.Object][protoobject], it will also inherit the default Joose.Meta.Object constructor:
var point1 = new Point({ x : 5, y : 7})
var point3d = new Point3D({ x : 5, y : 7, z : -5})
This constructor accepts a named argument pair for each attribute defined by the class. In this particular example, the attributes are required, and calling constructor without them will throw an error.
var point1 = new Point({ x : 5 }) //no y, kaboom!
From here on, we can use point and point3d just as you would any other JavaScript object.
This recipe demonstrates some basic Joose concepts, attributes, subclassing, and a simple method modifier.
The concept of method modifiers is directly ripped off from CLOS. A great explanation of them can be found by following this link
Nickolay Platonov nickolay8@gmail.com
Based on original Moose::Cookbook content, written by:
Stevan Little stevan@iinteractive.com
Dave Rolskyautarch@urth.org
Copyright (c) 2008-2011, Malte Ubl, Nickolay Platonov
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.