View helpers

Coaster provides functions and decorators for common scenarios in view handlers.

coaster.views.get_current_url()[source]

Return the current URL including the query string as a relative path.

coaster.views.get_next_url(referrer=False, external=False, session=False, default=[])[source]

Get the next URL to redirect to. Don’t return external URLs unless explicitly asked for. This is to protect the site from being an unwitting redirector to external URLs.

This function looks for a next parameter in the request or in the session (depending on whether parameter session is True). If no next is present, it checks the referrer (if enabled), and finally returns either the provided default (which can be any value including None) or url_for('index'). If your app does not have a URL endpoint named index, / is returned.

coaster.views.jsonp(*args, **kw)[source]

Returns a JSON response with a callback wrapper, if asked for.

coaster.views.load_model(model, attributes=None, parameter=None, workflow=False, kwargs=False, permission=None)[source]

Decorator to load a model given a query parameter.

Typical usage:

@app.route('/<profile>')
@load_model(Profile, {'name': 'profile'}, 'profileob')
def profile_view(profileob):
    # 'profileob' is now a Profile model instance. The load_model decorator replaced this:
    # profileob = Profile.query.filter_by(name=profile).first_or_404()
    return "Hello, %s" % profileob.name

Using the same name for request and parameter makes code easier to understand:

@app.route('/<profile>')
@load_model(Profile, {'name': 'profile'}, 'profile')
def profile_view(profile):
    return "Hello, %s" % profile.name

load_model aborts with a 404 if no instance is found. load_model also recognizes queries to url_name of BaseIdNameMixin instances and will automatically load the model. TODO: that should be handled by the model, not here.

Parameters:
  • model – The SQLAlchemy model to query. Must contain a query object (which is the default with Flask-SQLAlchemy)
  • attributes – A dict of attributes (from the URL request) that will be used to query for the object. For each key:value pair, the key is the name of the column on the model and the value is the name of the request parameter that contains the data
  • parameter – The name of the parameter to the decorated function via which the result is passed. Usually the same as the attribute
  • workflow – If True, the method workflow() of the instance is called and the resulting workflow object is passed to the decorated function instead of the instance itself
  • kwargs – If True, the original request parameters are passed to the decorated function as a kwargs parameter
  • permission – If present, load_model calls the permissions() method of the retrieved object with g.user as a parameter. If permission is not present in the result, load_model aborts with a 403. g is the Flask request context object and you are expected to setup a request environment in which g.user is the currently logged in user. Flask-Lastuser does this automatically for you
coaster.views.load_models(*chain, **kwargs)[source]

Decorator to load a chain of models from the given parameters. This works just like load_model() with some small differences.

Parameters:
  • chain – The chain is a list of tuples of (model, attributes, parameter). Lists and tuples can be used interchangeably. All retrieved instances are passed as parameters to the decorated function
  • workflow – Like with load_model(), workflow() is called on the last instance in the chain, and only the resulting workflow object is passed to the decorated function
  • kwargs – Same as in load_model()
  • permission – Same as in load_model(), except permissions() is called on every instance in the chain and the retrieved permissions are passed as the second parameter to the next instance in the chain. This allows later instances to revoke permissions granted by earlier instances

As an example, if a URL represents a hierarchy such as /<page>/<comment>, the page can assign edit and delete permissions, while the comment can revoke edit and retain delete if the current user owns the page but not the comment posted on it.

coaster.views.requestargs(*vars)[source]

Decorator that loads parameters from request.args if not specified in the function’s keyword arguments.

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