Updating Data
Saving changes to existing data
Editing a message
To demonstrate editing an existing item
in the database we can edit a message.
Create a template for editing a message
<form action="edit-message" method="post">
<label>Message</label>
<input name="message" type="text">
<input type="submit" value="Save">
</form>
Write a new template called edit-message.html
which contains a form for editable fields.
Include a hidden field for the id
<form action="edit-message" method="post">
<label>Message</label>
<input name="message" type="text">
<input name="message_id" type="hidden">
<input type="submit" value="Save">
</form>
This will help us know which table row
to update when the form is submitted.
Route for editing a message
@website.route('/edit-message')
@usermanager.login_required
def edit_message():
return render_template('edit-message.html')
Create a new route for the message editor
and display the correct template for it.
Set up the GET and POST methods
@website.route('/edit-message', methods=['GET', 'POST'])
@usermanager.login_required
def edit_message():
if request.method == 'GET':
return render_template('edit-message.html')
elif request.method == 'POST':
return redirect('/')
Pass the message id to the edit-message route
@website.route('/edit-message/<message_id>', methods=['GET', 'POST'])
@usermanager.login_required
def edit_message(message_id):
if request.method == 'GET':
return render_template('edit-message.html')
elif request.method == 'POST':
return redirect('/')
Load the message data in the route
if request.method == 'GET':
query_string = (
'SELECT message_id, content, user_id '
'FROM messages '
'WHERE message_id = ?'
)
query_result = datamanager.query_db(
query_string,
[message_id],
one=True
)
return render_template('edit-message.html')
Pass the message data to the template
return render_template('edit-message.html', message=query_result)
Pass the query result to the template
under the variable name message.
<form action="edit-message" method="post">
<label>Message</label>
<input name="message" type="text" value="{{ message.content }}">
<input name="message_id" type="hidden" value="{{ message.message_id }}">
<input type="submit" value="Save">
</form>
localhost:5000/edit-message/1
Browse to the edit-message url in your
browser and check that the message is showing.
The user can now make changes to the form
but the changes also need to be saved.
Make the message id optional so we can post
@website.route('/edit-message/<message_id>', methods=['GET', 'POST'])
@usermanager.login_required
def edit_message(message_id = None):
...
Write the POST processing
if request.method == 'POST':
message_content = request.form.get('message')
message_id = request.form.get('message_id')
query_string = (
'UPDATE messages '
'SET content = ? '
'WHERE message_id = ?'
)
query_result = datamanager.query_db(
query_string,
[message_content, message_id],
one=True
)
return redirect('/')
Check that it works
Edit a message in the browser
and check that it saves correctly.
Linking to an edit page
We can add a link to messages
that the user can click to edit.
Retrieve the message id for home page messages
@website.route('/')
def index():
query_string = (
'SELECT message_id, content, username, time_created '
'FROM messages INNER JOIN users '
'USING (user_id) '
'ORDER BY time_created DESC'
)
Update the query to load the message_id
so we can use it for our edit link.
Add a link to the message HTML
{% for message in messages %}
<li>
{{ message['username'] }}: {{ message['content'] }}
<a href="{{ url_for('edit_message', message_id = message['message_id']) }}">Edit</a>
</li>
{% endfor %}
Modify the index.html template to
include an edit link on the message.
Only show the edit link for the message owner
{% for message in messages %}
<li>
{{ message['username'] }}: {{ message['content'] }}
{% if current_user.username == message['username'] %}
<a href="{{ url_for('edit_message', message_id = message['message_id']) }}">Edit</a>
{% endif %}
</li>
{% endfor %}
Users should only be able to edit their
own messages, not messages by other people!
