Basic Grains

Views Grains

Views is the simplest type of grain, and it contains plain Flask route functions.

To generate a new views grain, run:

$ cob generate grain myview --type views

Views grains normally look like this:

$ cat myview.py

# cob: type=views mountpoint=/

from cob import route

@route('/sayhi')
def hi():
   return 'hi'

Blueprint Grains

Blueprint grains are very similar to views grains, but allow a more direct control over the blueprint they create:

$ cob generate grain blueprint --type blueprint
...
$ cat blueprint.py

# cob: type=blueprint mountpoint='/bp'
from flask import Blueprint

blueprint = Blueprint(...)

Note

You do not have to name your blueprint variable blueprint. Cob will look for your Blueprint instance among the module’s globals

Template Grains

Template grains are used to host Flask (Jinja2) templates:

$ cob generate grain templates --type templates
...

You can now create a basic template under templates/index.html. Rendering it is fairly simple:

$ cat index.py

# cob: type=views mountpoint=/
from cob import route
from flask import render_template

@route('/')
def index():
    return render_template('index.html')

Tasks Grains

Tasks grains are used to run Asyc tasks:

$ cob generate grain tasks --type tasks
...
$ cat tasks.py

# cob: type=tasks mountpoint={{mountpoint}}
from cob import task, periodic_task
from celery.schedules import crontab

## Your tasks go here

# use the next syntax for tasks you'll send "manually" through REST API
@task()
def task_func1(x,y,z ...):
        ...

# use this syntax to set a task binded to an non-default queue ("celery").
# queue arg can also be used with the periodic_task decorators.
@task(queue=<queue name>)
def task_func2(...):
        ...

# use this syntax to create a task that will be dispached every predefined period.
@periodic_task(every=<num of seconds>)
def periodic_task_func3(...):
        ...

schedule_dict = {
    '<choose a name>': {
             'schedule': crontab(...) or <number of seconds>,
             'args': <tuple of arguments according to the args your task_func needs>
    }
 }

 # use this syntax to create a more "complex" schedule for the task
 @periodic_task(schedule=schedule_dict)
 def periodic_task_func4(...):
        ...

Bundle Grains

In some cases, as we’ll see later, you may want to bundle several grains into a single directory. However, Cob only searches for grains in the project root by default.

Luckily you can create a directory and declare it as a bundle to tell Cob it should traverse the top level of that directory as well:

$ cob generate grain my_addon --type bundle
$ cat my_addon/.cob.yml
type: bundle
$ cob generate grain my_addon/index.py --type views
...