tgext.pluggable 0.1.2

Plug applications and extensions in a TurboGears2 project

About Pluggable Apps

tgext.pluggable permits to plug extensions and applications inside a TG projects much like the Django Apps.

Installing

tgext.pluggable can be installed both from pypi or from bitbucket:

easy_install tgext.pluggable

should just work for most of the users

Plugging Apps

In your application config/app_cfg.py import plug:

from tgext.pluggable import plug

Then at the end of the file call plug for each pluggable application you want to enable (package_name must be already installed in your python environment):

plug(base_config, 'package_name')

The plug function accepts various optional arguments, for example if the plugged application exposes a controller you can mount it in a different place specifying a different appid:

plug(base_config, 'package_name', 'new_app_id')

Other options include:

• plug_helpers (True/False) -> Enable helpers injection

• plug_models (True/False) -> Enable models plugging

• plug_controller (True/False) -> Mount pluggable app root controller

• plug_bootstrap (True/False) -> Enable websetup.bootstrap plugging

• plug_statics (True/False) -> Enable plugged app statics

• rename_tables (True/False) -> Rename pluggable tables by prepending appid.

Partials

tgext.pluggables provides a bunch of utilities to work with partials. Partials in tgext.pluggable can be declared as a function or TGController subclass method that has an @expose decorator. Those partials can lately be rendered with:

${h.call_partial('module:function_name', arg1='Something')}

In the case of a class method:

${h.call_partial('module.Class:method', arg1='Something')}

The quickstarted pluggable application provides an example partial:

from tg import expose

@expose('plugappname.templates.little_partial')
def something(name):
    return dict(name=name)

which can be rendered using:

${h.call_partial('plugappname.partials:something', name='Partial')}

Replacing Templates

tgext.pluggable provides a function to replace templates. This is useful when you want to override the template that an application you plugged in is exposing. To override call replace_template inside your application config:

from tgext.pluggable replace_template

replace_template(base_config, 'myapp.templates.about', 'myapp.templates.index')

replace_template will work even with tgext.pluggable partials, but won’t work with templates rendered directly calling the render method.

Calls to replace_template must be performed before the application has started.

Creating Pluggable Apps

tgext.pluggable provides a quickstart-pluggable command to create a new pluggable application:

$ paster quickstart-pluggable plugtest
Enter package name [plugtest]:
...

The quickstarted application will provide an example on how to use models, helpers, bootstrap, controllers and statics.

In the previous example the pluggable application can be enabled inside any TurboGears using:

plug(base_config, 'plugtest')

After enabling the plugtest application you should run paster setup-app development.ini inside your TurboGears project to create the sample model. Then you can access the sample application page though http://localhost:8080/plugtest

The plugme Entry Point

Pluggable applications are required to implement a plugme(app_config, options) entry point which will be called when plugging the application.

The plugme action is called before TurboGears configuration has been loaded so that it is possible to register more pluggables inside the plugme hook. This way a pluggable can plug any dependency it requires just by calling tgext.pluggable.plug inside its own plugme function.

Any options passed to the plug call will be available inside the options dictionary, other parts of the pluggable applications like controllers, models and so on will be imported after the call to plugme so that plugme can set any configuration options that will drive the behavior of the other parts.

Keep in mind that as plugme is called before loading the TurboGears configuration if you need to perform something based on any configuration file option you must register a setup from the plugme call and perform them there.

Accessing Application Models from Pluggable Apps

When creating a pluggable application you might often need to access to some models that have been declared inside the target application where the pluggable app will be mounted.

The most common use case for this is referencing the User, Group and Permission models. To do this tgext.pluggable provides an app_model object which wraps the application model and is initialized before loading the pluggable app.

This makes possible to access target application models referencing them as app_model.User or app_model.Group and so on. While you can guess that the primary key for those models is known (for the app_model.User object for example you might consider referencing to it as app_model.User.user_id) it is best practice to call the primary_key function provided by tgext.pluggable to get a reference to its column.

This way it is possibile to declare relations to models which are not provided by your pluggable app:

from tgext.pluggable import app_model, primary_key

user_id = Column(Integer, ForeignKey(primary_key(app_model.User)))
user = relation(app_model.User)

Pluggable Relative Urls

It is possible to generate an url relative to a pluggable mount point using the plug_url(pluggable, path, params=None, lazy=False) this function is also exposed inside the application helpers when a pluggable is used. For example to generate an url relative to the plugtest pluggable it is possible to call plug_url:

plug_url('plugtest', '/')

To perform redirects inside a pluggable app the plug_redirect(pluggable, path, params=None) function is provided. This function exposes the same interface as plug_url but performs a redirect much like tg.redirect.