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Persistence

This example implements another application which allows a user to leave Comments. Everything happens on one page though:

The home page first comes up with only a (somewhat prettied up) form asking the user to leave a comment:

A screenshot of a form with input for a user's email.

When the user clicks on submit, the new comment is persisted in the database. When the page is refreshed, the form is still rendered, but a list of all the comments in the database is shown below it:

A screenshot of a form with input for a user's email, and also a list of previously entered email addresses.

The example uses a CommentPostPanel widget as the container of everything shown on the home page. Its contents are: one CommentForm widget (used to post a new Comment), and several CommentBox widgets – one for each posted Comment.

Notice that Reahl provides versions of SqlAlchemy’s Session, Base and metadata objects for use with Reahl applications.

from __future__ import print_function, unicode_literals, absolute_import, division

from sqlalchemy import Column, UnicodeText, Integer
from reahl.sqlalchemysupport import Session, Base

from reahl.web.fw import UserInterface
from reahl.web.ui import Button
from reahl.web.ui import Form
from reahl.web.ui import InputGroup
from reahl.web.ui import LabelledBlockInput
from reahl.web.ui import P
from reahl.web.ui import Panel
from reahl.web.ui import TextInput
from reahl.web.ui import TwoColumnPage
from reahl.component.modelinterface import exposed, EmailField, Field, Event, Action


class PersistenceUI(UserInterface):
    def assemble(self):
        self.define_view('/', title='Persistence demo', page=HomePage.factory())


class HomePage(TwoColumnPage):
    def __init__(self, view):
        super(HomePage, self).__init__(view, style='basic')

        self.main.add_child(CommentForm(view))

        for comment in Session.query(Comment).all():
            self.main.add_child(CommentBox(view, comment))


class Comment(Base):
    __tablename__ = 'features_comment'
    
    id = Column(Integer, primary_key=True)
    email_address = Column(UnicodeText)
    text          = Column(UnicodeText)
    
    @exposed
    def fields(self, fields):
        fields.email_address = EmailField(label='Email address', required=True)
        fields.text          = Field(label='Comment', required=True)

    @exposed
    def events(self, events):
        events.submit = Event(label='Submit', action=Action(self.submit))

    def submit(self):
        Session.add(self)


class CommentForm(Form):
    def __init__(self, view):
        super(CommentForm, self).__init__(view, 'myform')

        new_comment = Comment()
        grouped_inputs = self.add_child(InputGroup(view, label_text='Leave a comment'))
        grouped_inputs.add_child( LabelledBlockInput(TextInput(self, new_comment.fields.email_address)) )
        grouped_inputs.add_child( LabelledBlockInput(TextInput(self, new_comment.fields.text)) )
        self.define_event_handler(new_comment.events.submit)
        grouped_inputs.add_child( Button(self, new_comment.events.submit) )


class CommentBox(Panel):
    def __init__(self, view, comment):
        super(CommentBox, self).__init__(view)
        self.add_child(P(view, text='By %s: %s' % (comment.email_address, comment.text)))
        

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