Forms and POST requests

Let’s add a simple form for creating new people, at the bottom of nodes/people/index.mak:

[...]

<hr />

<%! from warp.helpers import url %>
<p>
  Create a person: <br />
  <form method="post" action="${url(node, 'create')}">
    Name: <input type="text" name="name" /><br />
    Birthdate: <input type="text" name="birthdate" /> (YYYY-MM-DD)<br />
    <input type="submit" value="Create" />
  </form>
</p>

The only new thing here is the url helper, which just spits out a URL for the given node and facet (and args, if given).

Now we need to write the create facet, to actually create the person. We could of course just POST to the index page, and look for form values in the Mako template there. But that’s a little messy, and can lead to bugs when a page is refreshed.

So instead, we’ll write a pure Python facet to create the person, and then redirect the user to the new person’s view facet.

A POST Handler Facet

In nodes/people/people.py, add:

from datetime import datetime
from warp.runtime import store
from warp.helpers import url
from models import Person


def render_create(request):
    name = request.args["name"][0].decode("utf-8")
    birthdateStr = request.args["birthdate"][0]

    year, month, day = birthdateStr.split('-')
    birthdate = datetime(int(year), int(month), int(day))

    person = Person()
    person.name = name
    person.birthdate = birthdate

    store.add(person)
    store.commit()

    request.redirect(url(request.node, "view", [person.id]))

    return "Redirecting..."

Now you should be able to fill in the form on the index page, and create a new Person.

Error Handling

Let’s add a little bit of (very lazy) error handling to that form processing code:

from datetime import datetime
from warp.runtime import store
from warp.helpers import url, renderLocalTemplate
from models import Person


def render_create(request):

    name = request.args["name"][0]
    birthdateStr = request.args["birthdate"][0]

    try:

        name = name.decode("utf-8")

        if not name:
            raise ValueError("You must provide a name.")

        year, month, day = birthdateStr.split('-')
        birthdate = datetime(int(year), int(month), int(day))

    except Exception, e:

        return renderLocalTemplate(request, "index.mak",
                                   error=e,
                                   name=name,
                                   birthdate=birthdateStr)


    person = Person()
    person.name = name
    person.birthdate = birthdate

    store.add(person)
    store.commit()

    request.redirect(url(request.node, "view", [person.id]))
    return "Redirecting..."

Here we just catch anything that goes wrong in the argument munging. Then we use Warp’s renderLocalTemplate helper to re-render the index page. Note that we don’t have to give it the built-in variables like node, facet, and store – the helper adds those for you.

Back in nodes/people/index.mak, we’ll change the form to read like this:

<hr />

% if error:
  <div style="color: red; border: 1px solid red; padding: 5px">
    <strong>Error</strong>: ${error | h}
  </div>
% endif

<%! from warp.helpers import url %>
<p>
  Create a person: <br />
  <form method="post" action="${url(node, 'create')}">
    Name: <input type="text" name="name" value="${name or ''}" /><br />
    Birthdate: <input type="text" name="birthdate" value="${birthdate or ''}" /> (YYYY-MM-DD)<br />
    <input type="submit" value="Create" />
  </form>
</p>

This will display the error if there is one, and repopulate our two fields with whatever the user gave before.

Wasn’t that boring? Fortunately, you don’t actually have to write any of this for your regular CRUD – Warp can help.

Next: Warp’s CRUD Magic.