class/Mono.C5/UserGuideExamples/EventPatterns.cs

   1 /*
   2  Copyright (c) 2003-2008 Niels Kokholm and Peter Sestoft
   3  Permission is hereby granted, free of charge, to any person obtaining a copy
   4  of this software and associated documentation files (the "Software"), to deal
   5  in the Software without restriction, including without limitation the rights
   6  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   7  copies of the Software, and to permit persons to whom the Software is
   8  furnished to do so, subject to the following conditions:
   9
  10  The above copyright notice and this permission notice shall be included in
  11  all copies or substantial portions of the Software.
  12
  13  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  14  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  15  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  16  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  17  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  18  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  19  SOFTWARE.
  20 */
  21
  22 // C5 example: EventPatterns.cs for pattern chapter
  23
  24 // Compile with
  25 //   csc /r:C5.dll EventPatterns.cs
  26
  27 using System;
  28 using C5;
  29 using SCG = System.Collections.Generic;
  30
  31 namespace EventPatterns {
  32   class EventPatterns {
  33     public static void Main(String[] args) {
  34       UnindexedCollectionEvents();
  35       Console.WriteLine("--------------------");
  36       IndexedCollectionEvents();
  37       Console.WriteLine("--------------------");
  38       UpdateEvent();
  39     }
  40
  41     public static void UnindexedCollectionEvents() {
  42       ICollection<int> coll = new ArrayList<int>();
  43       ICollection<int> bag1 = new HashBag<int>();
  44       bag1.AddAll(new int[] { 3, 2, 5, 5, 7, 7, 5, 3, 7, 7 });
  45       // Add change handler
  46       coll.CollectionChanged
  47         += delegate(Object c)  {
  48              Console.WriteLine("Collection changed");
  49            };
  50       // Add cleared handler
  51       coll.CollectionCleared
  52         += delegate(Object c, ClearedEventArgs args) {
  53              Console.WriteLine("Collection cleared");
  54            };
  55       // Add added handler
  56       coll.ItemsAdded
  57         += delegate(Object c, ItemCountEventArgs<int> args) {
  58              Console.WriteLine("Item {0} added", args.Item);
  59            };
  60       // Add item count handler
  61       AddItemsAddedCounter(coll);
  62       AddItemsRemovedCounter(coll);
  63       coll.AddAll(bag1);
  64       coll.RemoveAll(new int[] { 2, 5, 6, 3, 7, 2 });
  65       coll.Clear();
  66       ICollection<int> bag2 = new HashBag<int>();
  67       // Add added handler with multiplicity
  68       bag2.ItemsAdded
  69         += delegate(Object c, ItemCountEventArgs<int> args) {
  70              Console.WriteLine("{0} copies of {1} added",
  71                                args.Count, args.Item);
  72            };
  73       bag2.AddAll(bag1);
  74       // Add removed handler with multiplicity
  75       bag2.ItemsRemoved
  76         += delegate(Object c, ItemCountEventArgs<int> args) {
  77              Console.WriteLine("{0} copies of {1} removed",
  78                                args.Count, args.Item);
  79            };
  80       bag2.RemoveAllCopies(7);
  81     }
  82
  83     // This works for all kinds of collections, also those with bag
  84     // semantics and representing duplicates by counting:
  85
  86     private static void AddItemsAddedCounter<T>(ICollection<T> coll) {
  87       int addedCount = 0;
  88       coll.ItemsAdded
  89         += delegate(Object c, ItemCountEventArgs<T> args) {
  90              addedCount += args.Count;
  91            };
  92       coll.CollectionChanged
  93         += delegate(Object c) {
  94              if (addedCount > 0)
  95                Console.WriteLine("{0} items were added", addedCount);
  96              addedCount = 0;
  97            };
  98     }
  99
 100     // This works for all kinds of collections, also those with bag
 101     // semantics and representing duplicates by counting:
 102
 103     private static void AddItemsRemovedCounter<T>(ICollection<T> coll) {
 104       int removedCount = 0;
 105       coll.ItemsRemoved
 106         += delegate(Object c, ItemCountEventArgs<T> args) {
 107              removedCount += args.Count;
 108            };
 109       coll.CollectionChanged
 110         += delegate(Object c) {
 111              if (removedCount > 0)
 112                Console.WriteLine("{0} items were removed", removedCount);
 113              removedCount = 0;
 114            };
 115     }
 116
 117     // Event patterns on indexed collections
 118
 119     public static void IndexedCollectionEvents() {
 120       IList<int> coll = new ArrayList<int>();
 121       ICollection<int> bag = new HashBag<int>();
 122       bag.AddAll(new int[] { 3, 2, 5, 5, 7, 7, 5, 3, 7, 7 });
 123       // Add item inserted handler
 124       coll.ItemInserted
 125         += delegate(Object c, ItemAtEventArgs<int> args)  {
 126              Console.WriteLine("Item {0} inserted at {1}",
 127                                args.Item, args.Index);
 128            };
 129       coll.InsertAll(0, bag);
 130       // Add item removed-at handler
 131       coll.ItemRemovedAt
 132         += delegate(Object c, ItemAtEventArgs<int> args)  {
 133              Console.WriteLine("Item {0} removed at {1}",
 134                                args.Item, args.Index);
 135            };
 136       coll.RemoveLast();
 137       coll.RemoveFirst();
 138       coll.RemoveAt(1);
 139     }
 140
 141     // Recognizing Update event as a Removed-Added-Changed sequence
 142
 143     private enum State { Before, Removed, Updated };
 144
 145     private static void AddItemUpdatedHandler<T>(ICollection<T> coll) {
 146       State state = State.Before;
 147       T removed = default(T), added = default(T);
 148       coll.ItemsRemoved
 149         += delegate(Object c, ItemCountEventArgs<T> args) {
 150              if (state==State.Before) {
 151                state = State.Removed;
 152                removed = args.Item;
 153              } else
 154                state = State.Before;
 155            };
 156       coll.ItemsAdded
 157         += delegate(Object c, ItemCountEventArgs<T> args) {
 158              if (state==State.Removed) {
 159                state = State.Updated;
 160                added = args.Item;
 161              } else
 162                state = State.Before;
 163            };
 164       coll.CollectionChanged
 165         += delegate(Object c)  {
 166              if (state==State.Updated)
 167                Console.WriteLine("Item {0} was updated to {1}",
 168                                  removed, added);
 169              state = State.Before;
 170            };
 171     }
 172
 173     public static void UpdateEvent() {
 174       ICollection<Teacher> coll = new HashSet<Teacher>();
 175       AddItemUpdatedHandler(coll);
 176       Teacher kristian = new Teacher("Kristian", "physics");
 177       coll.Add(kristian);
 178       coll.Add(new Teacher("Poul Einer", "mathematics"));
 179       // This should be caught by the update handler:
 180       coll.Update(new Teacher("Thomas", "mathematics"));
 181       // This should not be caught by the update handler:
 182       coll.Remove(kristian);
 183       coll.Add(new Teacher("Jens", "physics"));
 184       // The update handler is activated also by indexed updates
 185       IList<int> list = new ArrayList<int>();
 186       list.AddAll(new int[] { 7, 11, 13 });
 187       AddItemUpdatedHandler(list);
 188       list[1] = 9;
 189     }
 190   }
 191
 192   // Example class where objects may be equal yet display differently
 193
 194   class Teacher : IEquatable<Teacher> {
 195     private readonly String name, subject;
 196
 197     public Teacher(String name, String subject) {
 198       this.name = name; this.subject = subject;
 199     }
 200
 201     public bool Equals(Teacher that) {
 202       return this.subject.Equals(that.subject);
 203     }
 204
 205     public override int GetHashCode() {
 206       return subject.GetHashCode();
 207     }
 208
 209     public override String ToString() {
 210       return name + "[" + subject + "]";
 211     }
 212   }
 213 }