Module: Observable

Defined in:
lib/rubysl/observer/observer.rb

Overview

Implements the Observable design pattern as a mixin so that other objects can be notified of changes in state. See observer.rb for details and an example.

Instance Method Summary collapse

Instance Method Details

#add_observer(observer) ⇒ Object

Add observer as an observer on this object. observer will now receive notifications.



123
124
125
126
127
128
129
 
# File 'lib/rubysl/observer/observer.rb', line 123

def add_observer(observer)
  @observer_peers = [] unless defined? @observer_peers
  unless observer.respond_to? :update
    raise NoMethodError, "observer needs to respond to `update'"
  end
  @observer_peers.push observer
end

#changed(state = true) ⇒ Object

Set the changed state of this object. Notifications will be sent only if the changed state is true.



161
162
163
 
# File 'lib/rubysl/observer/observer.rb', line 161

def changed(state=true)
  @observer_state = state
end

#changed? ⇒ Boolean

Query the changed state of this object.



168
169
170
171
172
173
174
 
# File 'lib/rubysl/observer/observer.rb', line 168

def changed?
  if defined? @observer_state and @observer_state
    true
  else
    false
  end
end

#count_observers ⇒ Object

Return the number of observers associated with this object.



149
150
151
152
153
154
155
 
# File 'lib/rubysl/observer/observer.rb', line 149

def count_observers
  if defined? @observer_peers
    @observer_peers.size
  else
    0
  end
end

#delete_observer(observer) ⇒ Object

Delete observer as an observer on this object. It will no longer receive notifications.



135
136
137
 
# File 'lib/rubysl/observer/observer.rb', line 135

def delete_observer(observer)
  @observer_peers.delete observer if defined? @observer_peers
end

#delete_observers ⇒ Object

Delete all observers associated with this object.



142
143
144
 
# File 'lib/rubysl/observer/observer.rb', line 142

def delete_observers
  @observer_peers.clear if defined? @observer_peers
end

#notify_observers(*arg) ⇒ Object

If this object’s changed state is true, invoke the update method in each currently associated observer in turn, passing it the given arguments. The changed state is then set to false.



181
182
183
184
185
186
187
188
189
190
 
# File 'lib/rubysl/observer/observer.rb', line 181

def notify_observers(*arg)
  if defined? @observer_state and @observer_state
    if defined? @observer_peers
      @observer_peers.dup.each do |i|
        i.update(*arg)
      end
    end
    @observer_state = false
  end
end