The following session methods perform CRUD Operations −
- DBSession.add(model object) − inserts a record into mapped table.
- DBSession.delete(model object) − deletes record from the table.
- DBSession.query(model).all() − retrieves all the records from table (corresponding to a SELECT query).
You can apply filter to the retrieved record set by using a filter attribute. For instance, in order to retrieve records with city = ’Hyderabad’ in students table, use the following statement −
DBSession.query(model.student).filter_by(city = ’Hyderabad’).all()We shall now see how to interact with the models through controller URLs.
First let us design a ToscaWidgets form for entering the student’s data
Hello\hello\controllers.studentform.py
import tw2.core as twc import tw2.forms as twf class StudentForm(twf.Form): class child(twf.TableLayout): name = twf.TextField(size = 20) city = twf.TextField() address = twf.TextArea("",rows = 5, cols = 30) pincode = twf.NumberField() action = '/save_record' submit = twf.SubmitButton(value = 'Submit')In the RootController (root.py of Hello application), add the following function mapping ‘/add’ URL −from hello.controllers.studentform import StudentForm class RootController(BaseController):
@expose('hello.templates.studentform') def add(self, *args, **kw): return dict(page='studentform', form = StudentForm)Save the following HTML code as studentform.html in the templates folder −<!DOCTYPE html>
<html xmlns = "http://www.w3.org/1999/xhtml" xmlns:py = "http://genshi.edgewall.org/" lang = "en"> <head> <title>Student Registration Form</title> </head> <body> <div id = "getting_started"> ${form.display(value = dict(title = 'Enter data'))} </div> </body> </html>Enter http://localhost:8080/add in the browser after starting the server. The following Student information form will open up in the browser −
The above form is designed to be submitted to the ‘/save_record’ URL. Hence a save_record() function needs to be added in the root.py to expose it. The data from the studentform is received by this function as a dict() object. It is used to add a new record in the student table underlying student model.@expose() #@validate(form = AdmissionForm, error_handler = index1) def save_record(self, **kw): newstudent = student(name = kw[‘name’],city = kw[‘city’], address = kw[‘address’], pincode = kw[‘pincode’]) DBSession.add(newstudent) flash(message = “new entry added successfully”) redirect(“/listrec”)
Please note that after the successful addition, the browser will be redirected to ‘/listrec’ URL. This URL is exposed by a listrec() function. This function selects all records in the student table and sends them in the form of a dict object to the studentlist.html template. This listrec() function is as follows −
@expose ("hello.templates.studentlist") def listrec(self): entries = DBSession.query(student).all() return dict(entries = entries)The studentlist.html template iterates through the entries dictionary object using py:for directive. The studentlist.html template is as follows −
<html xmlns = "http://www.w3.org/1999/xhtml" xmlns:py = "http://genshi.edgewall.org/"> <head> <link rel = "stylesheet" type = "text/css" media = "screen" href = "${tg.url('/css/style.css')}" /> <title>Welcome to TurboGears</title> </head> <body> <h1>Welcome to TurboGears</h1> <py:with vars = "flash = tg.flash_obj.render('flash', use_js = False)"> <div py:if = "flash" py:replace = "Markup(flash)" /> </py:with> <h2>Current Entries</h2> <table border = '1'> <thead> <tr> <th>Name</th> <th>City</th> <th>Address</th> <th>Pincode</th> </tr> </thead> <tbody> <py:for each = "entry in entries"> <tr> <td>${entry.name}</td> <td>${entry.city}</td> <td>${entry.address}</td> <td>${entry.pincode}</td> </tr> </py:for> </tbody> </table> </body> </html>Now revisit the http://localhost:8080/add and enter data in the form. By clicking on the submit button, it will take the browser to studentlist.html. It will also flash a ‘new record added successfully’ message.
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