Introduction
jzForm is a package that aims to do for user input what CSS did for web
design — seperate content from presentation.
Its goal it is to allow one program or one part of a program to
declare what kind of data it need back, another to format that request for
display to the user, and a third to provide the answer. It provides
functionality for verifying that data returned matched the request. The hope
is that this program will take care of a lot of the back and forth between
programs and their ultimate users.
jzForm was designed with web based applications in mind and so used the HTML
term ‘form’ to describe the intended output, but there is noting in jzForm that
requires a form actually be produced. It was designed to enable machines as
well as real users to respond to a request.
Philosophy
NOTE: Not all feature are currently implented
jzForm breaks the process of building a form up into three distinct functions:
Discribing the data to be returned, formatting an appropriate view to request
that data, and dealing with the returned values.
Describe the Data
Good design dictates that the buisness logic of a program and the user interface
should not be mixed. This is expressed in MVC web frameworks like Rails and
Merb. The model section in these cases should never be involved in creating
HTML. But, it is often this modle layer that knows what external data it needs.
In the simple case the controller and view layers assume that they know what
information is needed, either because it is hard coded into the application,
or by inspecting some feature of the model class. Both cases are suboptimal.
The former actually moves the logic around what information is needed into the
view layer and freezes it there. The form must be modified or rewritten if
the needed information changes in development, and there is no way for the
buisness logic to change the form at run time. (At least not without putting
too much logic into the view.)
jzForm allows the mnodel layer to describe to the Controller precisly what
information it need to collect. It can do this without regard for how any
other layer will eventually present this request and retrieve the information.
There are two options for describing this data. One is to build up a JZForm
Object. This class provides convient methods fro adding fields, setting
validation conditions and managing data.
The other is to create a textual representation of a jzForm. jzForm has a
standard format that can be represented in JSON, YAML, or XML. This means
that the program that requests the information need not even run Ruby or be in
the local memory space.
Present the Form
JZForm uses templates to render its forms. The package ships with templates
written in ruby the render a basic HTML form and a pacakge that will render
the form to a text console. It also ships with a Javascript package that can
create a form from a JSON object.
The presentation can easily be customized with user designed templates an
application, form, or even field level.
Return Valid Data
Finally, when data is returned, it needs to be validated. jzForm takes
care of this step automatically based on provide rules. When one retrieves a
value from a JZForm object, one can be sure that it within the constraints that
were set for it. This closes one of the most common sources of security
breaches, namely failing to properly validate user input. By ceneralizing the
chanel that user generated data flows throught and building validating directly
on to that channel it is antisipated that such errors will be dramitically
reduced.
Examples
In the example folder there is a file, form_test.rb, that will run jzforms. It
is a merb “very flat app” and is run with ‘merb -I example/form_test.rb’.
There are a couple different forms in the file. A get request to localhost:4000
will show the from. submiting that form will show the params that it generated.
As validations and subforms get implimented, more will be added here.