Signals¶

Using Signals¶

To receive a signal, all you need is a function that can accept keyword arguments:

>>> def receiver(**kw):
...   print "Look what I got!", kw
...

Receiving functions are connected to one or more signals you’d like to receive:

>>> from flatland import signals
>>> signals.validator_validated.connect(receiver)

That’s it. Now each time flatland runs a validator, the receiver function will be called and passed some information about the validation that just occured. There is no limit to the number of receivers connected to a signal.

Built-In Signals¶

signals.validator_validated¶

Emitted after a validator has processed an element.

Parameters:	sender – the validator element – the element being validated state – the state passed to validate() result – the result of validator execution

Signal API¶

signal(self, name, doc=None)¶

Return the NamedSignal name, creating it if required.

class Signal(doc=None)¶

A generic notification emitter.

ANY¶

A symbol for “receive a signal sent by any sender”.

receivers¶

A mapping from internal Signal receiver ids to signal receivers or their weak references if the receiver connected with weak=True.

connect(receiver, sender=ANY, weak=True)¶

Connect receiver to signal events send by sender.

Parameters:

receiver – A callable. Will be invoked by send(). Will be invoked with sender= as a named argument and any **kwargs that were provided to a call to send(). sender – Any object or Signal.ANY. Restricts notifications to receiver to only those send() emissions sent by sender. If ANY, the receiver will always be notified. A receiver may be connected to multiple sender on the same Signal. Defaults to ANY. weak – If true, the Signal will hold a weakref to receiver and automatically disconnect when receiver goes out of scope or is garbage collected. Defaults to True.

disconnect(receiver, sender=ANY)¶

Disconnect receiver from this signal’s events.

has_receivers_for(sender)¶

True if there is probably a receiver for sender.

Performs an optimistic check for receivers only. Does not guarantee that all weakly referenced receivers are still alive. See receivers_for() for a stronger search.

receivers_for(sender)¶

Iterate all live receivers listening for sender.

send(sender=None, **kwargs)¶

Emit this signal on behalf of sender, passing on **kwargs.

Returns a list of 2-tuples, pairing receivers with their return value. The ordering of receiver notification is undefined.