Hi Mick
I'm far from being an expert but I'll try and be helpful..
web2py follows the Model-View-Controller arrangement for web
applications. This approach is now common in many web frameworks
because it allows you to separate different aspects of the
application. In a large project they might be worked on by different
people with different skills, somewhat independently of each other.
Model - the way the data that's stored by the application is arranged
(could be done by a database specialist)
View - the way the web application looks and interacts with the user
(web design & javascript specialist)
Controller - all the 'program' that sits between the Model and the
View, getting the right data for the user to see, allowing them to
fill in forms etc. and storing new information back into the database
(programming specialist)
Controller functions have a view associated with them. Generally
controllers will get some information from the database and present it
to the user (by passing it to the view). Part of this might be a form
that allows the user to add more information to the database or update
information. The controller will handle the contents of the form and
update the database using information defined in the model.
In the example 'db' is a variable that is called to access the
database (as set up in the model file). I wouldn't worry too much
about what is happening behind the scenes for now - if you use the
examples with your own example application you should see get a feel
for how to use the framework.
For example to take one of the simpler example controller functions:
(as typed here might have copying mistakes)
def show():
id=request.vars.id
recipes=db(db.recipe.id==id).select()
if not len(recipes): redirect((URL(r=request,f='recipes'))
return dict(recipe=recipes[0])
This function is called when the user visits http://my.application.com/show?id=1
The variable 'request' contains information that came from the user's
web browser.
The 'id' variable passed at the end of the URL is stored in another
variable, 'id', just as shorthand to make the rest of the function
simpler.
the 'recipes=' line executes a select query on the database, fetching
the recipes that have 'id' = 1 and putting the resulting rows into the
variable 'recipes'.
''if not len(recipes)...' checks that at least one row was returned.
If no rows were returned then the user is redirected to a page listing
all recipes. The 'redirect' function uses an exception that means the
show() function is quit at this point and the next line won't be
processed in this case.
Finally the 'return' passes the recipe information to the view as a
dictionary. The view will be constructed to know how to present the
different recipe fields.
Like other frameworks, web2py gives you a set of tools that add web-
related functionality (or an API). To use it you need to learn what
tools are available and how to use them together, but not necessarily
what is going on behind the scenes.
The cookbook is good, but contains a lot less description and
information than the web2py manual, which is available in PDF form for
a very reasonable price http://www.lulu.com/content/4968879
Chris
On Jan 16, 11:30 pm, mickgardner <[email protected]> wrote:
> Hi there,
>
> firstly wanted to say thanks to the developers for building such a
> fantastic and easy to use web framework i especially like the
> intuitiveness of the design and web application development
> interface.
>
> Secondly, an introduction and some questions.
>
> I've been trying to learn django for a few weeks now by way of
> building my own blog. I got to a decent stage where the blog would
> actually be functional but I was constantly troubled by the django
> 'newforms'. Its honestly a dazzling array of functions and code that
> was beyond my ability to learn.
>
> I've recently undertaken at the age of 32/33 to teach myself
> programming, having been in the web and IT industries for over ten
> years as an analyst. I've got to the stage where I can build a few
> decent console python applications & scripts, use classes, modules,
> and create functions - and have a basic level understanding of object
> oriented programming.
>
> But django newforms was just beyond me!
>
> Enter Web2py, I've been working through the cookbook plus pdf file. I
> got to page 11/12 "creating functions(Actions" and hit a small road
> block:
>
> Question: how does one learn how to build / develop / understand the
> controllers? I looked at the code in 11/12 and wondered what it meant
> exactly, this may be slightly made worse by the fact that the db in
> the example is actually called 'db'. Was there a function called 'db'
> in the code provided? How does one best learn to develop the
> controllers and learn what the various functions in the example are?
>
> Thanks for getting this far in your reading :-)
>
> I hope I can learn from you all in some way and help contribute if I
> can.
>
> Kind regards
>
> mickgardner
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