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Getting an object from a SQLAlchemy model or abort

By Jérôme Pigeot filed in Database

A simple shortcut which let you returning an abort code when the wanted object is not found.

This kind of trick is already integrated in the Flask-SQLAlchemy extension (with the get_or_404() method) so it's just usefull if you're using SQLAlchemy natively...

Here's the code:

def get_or_abort(model, object_id, code=404):
    """
    get an object with his given id or an abort error (404 is the default)
    """
    result = model.query.get(object_id)
    return result or abort(code)

And now how to use it in your app:

def theme_detail(theme_id):
    # shows a theme
    theme = get_or_abort(Theme, theme_id)
    return render_template('theme_detail.html', theme=theme)

This snippet by Jérôme Pigeot can be used freely for anything you like. Consider it public domain.

Comments

Slightly improved version by Dag Odenhall on 2010-09-03 @ 20:00
abort() raises an exception and is not something you return. Also you'll want to check if result is None or you'll abort for "nonzero" values (False, 0, '', …). Don't know if this is an actual problem, but is None is a best practice, regardless.
```
def get_or_404(model, ident):
    rv = model.query.get(ident)
    if rv is None:
        abort(404)
    return rv
```
comment by Jérôme Pigeot on 2010-09-13 @ 20:25
thanks for the info, i'll take care to correct my code.