Building responses

As we saw in the Request chapter, Emmett provides several tools for handling requests from clients.

However, since your application has to produce responses to these requests, Emmett also supplies some tools for that.

The response object

As for the request object, Emmett stores some data in the response object, data which will be used when the request has been processed and the output is pushed back to the client.

Accessing the response object is as simple as accessing a request:

from emmett import response

and this is the list of attributes you can deal with:

attribute	description
status	HTTP status for the response, set on 200 unless an exception/redirect/abort occurs
cookies	contains the cookies that will be pushed to the client
headers	HTTP headers for the response
meta	meta tags for the response
meta_prop	meta properties tags for the response

If you need to set a cookie you can just write:

response.cookies['yourcookiename'] = 'yourdata'
response.cookies['yourcookiename']['path'] = '/'

or to set a header:

response.headers['Cache-Control'] = 'private'

Meta properties

HTML has 2 kind of meta tags:

<meta property="og:title" content="Walter Bishop's place" />
<meta name="description" content="A pocket universe" />

they can be very helpful for improving your application's SEO.

Instead of manually writing them in your templates, you can add these tags to your response in an easier way. Lets say, for example, that we have a blog and we want to automatically add our meta tags on a single post:

@app.route("/p/<int:post_id>")
async def single(post_id):
    post = somedb.findmypost(post_id)
    response.meta.title = "MyBlog - "+post.title
    response.meta.keywords = ",".join(key for key in post.keywords)
    response.meta_prop["og:title"] = response.meta.title

Then, in your template, you can just write:

<html>
  <head>
    <title>{{ =current.response.meta.title }}</title>
    {{ include_meta }}
  </head>

and you will have all the meta tags included in your HTML.

Message flashing

When you need to store a message at the end of one request, and access it during the next one, Emmett's response.alerts() become quite handy.

For example, you may want to send a success alert to the user. Let's say you have function which exposes a form, you can use message flashing to alert the user the form was accepted:

from emmett.helpers import flash

@app.route("/someurl")
async def myform():
    form = await Form()
    if form.accepted:
        flash("We stored your question!")
    return dict(form=form)

then, in your template, you can access the flashed messages using response:

<div class="container">
  {{ for flash in current.response.alerts(): }}
  <div class="myflashstyle">{{ =flash }}</div>
  {{ pass }}
</div>

and style them however you prefer.

flash() and response.alerts() also accept category filtering, so you can do:

flash('message1', 'error')
response.alerts(category_filter=["error"])

or you can receive all flash messages with their category:

>>> response.alerts(with_categories=True)
[('error', 'message1')]

The response object
Meta properties
Message flashing