/src/lib/abilities/observable.e

 1-- This file is part of a Liberty Eiffel library.
 2-- See the full copyright at the end.
 3--
 4deferred class OBSERVABLE
 5   --
 6   -- Part of the ''Observer'' Design Pattern. An object of this class should notify its observers whenever its
 7   -- state changes. Use the `notify' feature for that.
 8   --
 9   -- See also OBSERVER.
10   --
11
12feature {ANY}
13   add (o: OBSERVER[like Current])
14         -- Add an observer that should be notified
15      do
16         observers.add_last(o)
17      end
18
19   remove (o: OBSERVER[like Current])
20         -- Remove an observer that should not be notified anymore
21      require
22         has(o)
23      local
24         i: INTEGER
25      do
26         i := observers.first_index_of(o)
27         observers.remove(i)
28      end
29
30   has (o: OBSERVER[like Current]): BOOLEAN
31         -- True if the observer will be notified when the state of Current changes
32      do
33         Result := observers.has(o)
34      end
35
36feature {}
37   notify
38         -- Notify all the observers that the state of Current changed
39      do
40         observers.for_each(agent {OBSERVER[like Current]}.update(Current))
41      end
42
43feature {}
44   observers: COLLECTION[OBSERVER[like Current]]
45         -- The collection of observers
46
47invariant
48   notifiable: observers /= Void
49
50end -- class OBSERVABLE
51--
52-- Copyright (C) 2009-2017: by all the people cited in the AUTHORS file.
53--
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58-- copies of the Software, and to permit persons to whom the Software is
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60--
61-- The above copyright notice and this permission notice shall be included in
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63--
64-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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