This class manages a list of callbacks.
Callbacks are managed by the class CallbackList. When they are added, a priority (just a number or anything Comparable with other priorities) is specified. The biggest the priority is, the earliest the callback will be considered.
Callbacks are processed for a given set of objects as long as they return false. If you want to stop processing, you must return true. Example :
cbl = CallbackList.new c1 = false c2 = false c3 = false cbl.add(10) { c1 = true; 1 } cbl.add(5) { c2 = true; true } cbl.add(0) { c3 = true } cbl.process('aa') puts "#{c1} #{c2} #{c3}"
This example would display “true true false” as callbacks processing was stopped after the second callback returned true.
In XMPP4R, callbacks' priorities are quite normalized since we want to be able to “cascade” callbacks in a clean way. Here are values your code should take into account :
logging & debugging callbacks. Those callbacks should not consume elements.
Where Helpers register their callbacks. The normal value is 100, and Helpers shouldn't register something else unless there's a very good reason to.
all those numbers are normally available for your application. That's enough, don't you think ?
Create a new list of callbacks
# File lib/xmpp4r/callbacks.rb, line 45 def initialize @list = [] end
Add a callback to the list
List will be sorted afterwards
the callback's priority, the higher, the sooner.
the callback's reference
a block to execute
The list, for chaining
# File lib/xmpp4r/callbacks.rb, line 58 def add(prio = 0, ref = nil, proc = nil, &block) block = proc if proc @list.push(Callback.new(prio, ref, block)) @list.sort! { |a, b| b.priority <=> a.priority } self end
Delete a callback by reference
the reference of the callback to delete
The list, for chaining
# File lib/xmpp4r/callbacks.rb, line 69 def delete(ref) @list.delete_if { |item| item.ref == ref } self end
# File lib/xmpp4r/callbacks.rb, line 74 def each(&block) @list.each(&block) end
Number of elements in the list
The number of elements
# File lib/xmpp4r/callbacks.rb, line 81 def length @list.length end
Process an element through all my callbacks. returns e.consumed?
The elements to pass to the callback. You can pass
several, but of course, you block must know how to handle them.
true if the element has been consumed
# File lib/xmpp4r/callbacks.rb, line 90 def process(*e) # If somebody adds a new callback the list will get modified # and sorted(!) while still iterating through it. So we use a # local copy of @list. Any freshly added callback will receive # the next stanzas, not the current. list = @list.dup # process through callbacks list.each do |item| return true if item.block.call(*e) == true end false end