Class: Jabber::CallbackList

Class | Jabber::CallbackList
In: | lib/xmpp4r/callbacks.rb
Parent: | Object

This class manages a list of callbacks.

## Callbacks management and priority

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 :

>= 200: | logging & debugging callbacks. Those callbacks should not consume elements.
100-199: | 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.
< 100: | all those numbers are normally available for your application. That‘s enough, don‘t you think ?

### Methods

add delete length new process

### Public Class methods

new()

Create a new list of callbacks

[Source]

        # File lib/xmpp4r/callbacks.rb, line 44
    44:     def initialize
    45:       @list = []
    46:     end

### Public Instance methods

add(prio = 0, ref = nil, proc = nil, &block)

Add a callback to the list

List will be sorted afterwards

prio: | [Integer] the callback‘s priority, the higher, the sooner.
ref: | [String] the callback‘s reference
block: | [Block] a block to execute
return: | [Jabber::CallbackList] The list, for chaining

[Source]

        # File lib/xmpp4r/callbacks.rb, line 57
    57:     def add(prio = 0, ref = nil, proc = nil, &block)
    58:       block = proc if proc
    59:       @list.push(Callback.new(prio, ref, block))
    60:       @list.sort! { |a, b| b.priority <=> a.priority }
    61:       self
    62:     end

delete(ref)

Delete a callback by reference

ref: | [String] the reference of the callback to delete
return: | [CallBackList] The list, for chaining

[Source]

        # File lib/xmpp4r/callbacks.rb, line 68
    68:     def delete(ref)
    69:       @list.delete_if { |item| item.ref == ref }
    70:       self
    71:     end

length()

Number of elements in the list

return: | [Integer] The number of elements

[Source]

        # File lib/xmpp4r/callbacks.rb, line 76
    76:     def length
    77:       @list.length
    78:     end

process(*e)

Process an element through all my callbacks. returns e.consumed?

e: | [Object] The elements to pass to the callback. You can pass

several, but of course, you block must know how to handle them.

return: | [Boolean] true if the element has been consumed

[Source]

        # File lib/xmpp4r/callbacks.rb, line 85
    85:     def process(*e)
    86:       # If somebody adds a new callback the list will get modified
    87:       # and sorted(!) while still iterating through it. So we use a
    88:       # local copy of @list. Any freshly added callback will receive
    89:       # the next stanzas, not the current.
    90:       list = @list.dup
    91:
    92:       # process through callbacks
    93:       list.each do |item|
    94:         return true if item.block.call(*e) == true
    95:       end
    96:       false
    97:     end

[Validate]