CallbackList is the fundamental class in eventpy. The other classes EventDispatcher and EventQueue are built on CallbackList.
CallbackList holds a list of callbacks. At the time of the call, CallbackList simply invokes each callback one by one. Consider CallbackList as the signal/slot system in Qt, or the callback function pointer in some Windows APIs (such as lpCompletionRoutine in ReadFileEx).
The callback can be any callback target -- functions, member functions (methods), lambda, and any object defined __call__.
import eventpy.callbacklist
CallbackList(policy = eventpy.policy.defaultPolicy)policy: the policy to configure and extend the callback list. The default value is eventpy.policy.defaultPolicy. See document of policies for details.
empty()Return true if the callback list is empty.
Note: in multi threading, this function returning true doesn't guarantee that the list is empty. The list may immediately become non-empty after the function returns true.
append(callback)Add the callback to the callback list.
The callback is added to the end of the callback list.
Return a handle that represents the callback. The handle can be used to remove this callback or to insert additional callbacks before this callback.
If append is called in another callback during the invoking of the callback list, the new callback is guaranteed not to be triggered during the same callback list invoking.
The time complexity is O(1).
prepend(callback)Add the callback to the callback list.
The callback is added to the beginning of the callback list.
Return a handle that represents the callback. The handle can be used to remove this callback or to insert additional callbacks before this callback.
If prepend is called in another callback during the invoking of the callback list, the new callback is guaranteed not to be triggered during the same callback list invoking.
The time complexity is O(1).
insert(callback, before)Insert the callback to the callback list before the callback handle before. If before is not found, callback is added at the end of the callback list.
Return a handle that represents the callback. The handle can be used to remove this callback or to insert additional callbacks before this callback.
If insert is called in another callback during the invoking of the callback list, the new callback is guaranteed not to be triggered during the same callback list invoking.
The time complexity is O(1).
remove(handle)Remove the callback handle from the callback list.
Return true if the callback is removed successfully, false if the callback is not found.
The time complexity is O(1).
forEach(func)Apply func to all callbacks.
The func can be one of the two prototypes:
func(handle, callback)
func(callback)handle is the handle returned by append, prepend, or insert.
callback is the callback added in the callback list.
Note: the func can remove any callbacks, or add other callbacks, safely.
forEachIf(func)Apply func to all callbacks. func must return a boolean value, and if the return value is false, forEachIf stops the looping immediately.
Return true if all callbacks are invoked, or event is not found, false if func returns false.
func has the same prototype as in forEach.
__call__(*args, **kwargs) const;Invoke each callbacks in the callback list.
The callbacks are called with arguments args and kwargs.
The callbacks are called in the thread same as the callee.
- If a callback adds another callback to the callback list during a invoking, the new callback is guaranteed not to be triggered within the same invoking. This is guaranteed by an integer counter. This rule will be broken is the counter is overflowed to zero in a invoking, but this rule will continue working on the subsequence invoking.
- Any callbacks that are removed during a invoking are guaranteed not triggered.
- All above points are not true in multiple threading. That's to say, if one thread is invoking a callback list, the other thread add or remove a callback, the added or removed callback may be called during the invoking.
append: O(1)prepend: O(1)insert: O(1)remove: O(1)