Changes between Version 13 and Version 14 of Signals


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Timestamp:
10/05/2006 01:45:56 AM (8 years ago)
Author:
anonymous
Comment:

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  • Signals

    v13 v14  
    5353 3. Use the dispatcher's `connect` signal to tell the dispatcher you want to listen for something.
    5454
    55 A good example of this is found in Django's bundled "contenttypes" application, which creates and maintains a registry of all the installed models in your database. In order to do this, the contenttypes app defines a `ContentType` model, and it needs to know any time a new model is installed so it can create the appropriate `ContentType` object for that model. To do this, it includes a file called `mnagement.py`; whenever `manage.py syncdb` is run, it loops through ''every'' application in the `INSTALLED_APPS` setting, and looks to see if any apps contain a module called `management`; if they do, `manage.py` imports them before installing any models, which means that any dispatcher connections listed in an app's `management` module will be set up before model installation happens.
     55A good example of this is found in Django's bundled "contenttypes" application, which creates and maintains a registry of all the installed models in your database. In order to do this, the contenttypes app defines a `ContentType` model, and it needs to know any time a new model is installed so it can create the appropriate `ContentType` object for that model. To do this, it includes a file called `management.py`; whenever `manage.py syncdb` is run, it loops through ''every'' application in the `INSTALLED_APPS` setting, and looks to see if any apps contain a module called `management`; if they do, `manage.py` imports them before installing any models, which means that any dispatcher connections listed in an app's `management` module will be set up before model installation happens.
    5656
    5757In its `management.py` file, the contenttypes app defines a function called `create_contenttypes`, which takes three arguments: `app`, `created_models` and `verbosity`. These correspond to the extra arguments `manage.py` will use with `dispatcher.send` when it sends the `post_syncdb` signal after installing each new application, and provide enough information to determine which models need to have new `ContentType` objects created (actually, just `app` and `created_models` would be enough; the extra argument, `verbosity`, is used by `manage.py` to indicate whether any listening functions should be "verbose" and echo output to the console, or be quiet and not echo any output.
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