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diff --git a/usth/ICT2.7/P3L3 Design Patterns Subtitles/5 - Factory Method Pattern - lang_en_vs5.srt b/usth/ICT2.7/P3L3 Design Patterns Subtitles/5 - Factory Method Pattern - lang_en_vs5.srt deleted file mode 100644 index c7ebddd..0000000 --- a/usth/ICT2.7/P3L3 Design Patterns Subtitles/5 - Factory Method Pattern - lang_en_vs5.srt +++ /dev/null @@ -1,179 +0,0 @@ -1 -00:00:00,012 --> 00:00:02,350 -Let's now look at the first design pattern that we - -2 -00:00:02,350 --> 00:00:05,700 -will discuss, the factory method pattern. And I'm going to start - -3 -00:00:05,700 --> 00:00:09,220 -by discussing the intent of the pattern and its applicability. - -4 -00:00:09,220 --> 00:00:12,210 -As far as the intent is concerned, the factory method pattern - -5 -00:00:12,210 --> 00:00:16,690 -allows for creating objects without specifying their class, by invoking - -6 -00:00:16,690 --> 00:00:19,370 -what we call a factory method. And what that is, is - -7 -00:00:19,370 --> 00:00:22,680 -a method whose main goal is to create class instances. - -8 -00:00:22,680 --> 00:00:25,510 -So when is this pattern useful? So when is it applicable? - -9 -00:00:25,510 --> 00:00:28,080 -For example, it is applicable in cases in which a class - -10 -00:00:28,080 --> 00:00:31,890 -cannot anticipate the type of object it must create. That is, - -11 -00:00:31,890 --> 00:00:34,800 -the type of an object is not known at compile time, - -12 -00:00:34,800 --> 00:00:37,800 -is not known until the code runs. A typical example of - -13 -00:00:37,800 --> 00:00:40,500 -this, are frameworks. So if you ever used a framework, you - -14 -00:00:40,500 --> 00:00:44,280 -will know that, normally, frameworks only know about interfaces and abstract - -15 -00:00:44,280 --> 00:00:47,450 -classes. So the exact type of the objects of these classes - -16 -00:00:47,450 --> 00:00:50,840 -is only known at runtime. The second case in which the factory - -17 -00:00:50,840 --> 00:00:53,835 -method pattern is applicable, is when a class wants its - -18 -00:00:53,835 --> 00:00:57,160 -subclasses to specify the type of objects it creates. And we'll - -19 -00:00:57,160 --> 00:00:59,920 -see an example of this in a minute. Finally, factory - -20 -00:00:59,920 --> 00:01:03,580 -method patterns are applicable when a class needs control over the - -21 -00:01:03,580 --> 00:01:06,760 -creation of its objects. And in this case, one possible - -22 -00:01:06,760 --> 00:01:09,380 -example is when there is a limit on the number of - -23 -00:01:09,380 --> 00:01:12,930 -objects that can be created. Special example, it's a singleton. If - -24 -00:01:12,930 --> 00:01:15,840 -you're familiar with a singleton, a singleton is a class for - -25 -00:01:15,840 --> 00:01:18,930 -which only one instance can be created. The factory method pattern - -26 -00:01:18,930 --> 00:01:21,760 -is perfect in these cases, because it allows to control how many - -27 -00:01:21,760 --> 00:01:24,640 -objects get created. So in this case, it would allow the creation - -28 -00:01:24,640 --> 00:01:27,290 -only of a single object. And from the second time that it - -29 -00:01:27,290 --> 00:01:30,040 -is invoked, it will just return the object that was previously - -30 -00:01:30,040 --> 00:01:33,700 -created. Now let's go ahead and see how this pattern actually works, - -31 -00:01:33,700 --> 00:01:37,100 -and let's do that by discussing the structure and the participants for - -32 -00:01:37,100 --> 00:01:41,330 -the pattern. The structure that is represented here, using the UML notation, - -33 -00:01:41,330 --> 00:01:45,530 -includes three classes, the Creator, the ConcreteCreator, - -34 -00:01:45,530 --> 00:01:48,000 -and the Product. The Creator provides the - -35 -00:01:48,000 --> 00:01:50,710 -interface for the factory method. So this - -36 -00:01:50,710 --> 00:01:53,200 -here, is the interface for the factory method - -37 -00:01:53,200 --> 00:01:55,950 -that, when invoked, returns an object of - -38 -00:01:55,950 --> 00:01:59,440 -type Product. The ConcreteCreator provides the actual - -39 -00:01:59,440 --> 00:02:02,350 -method for creating the Product. So this - -40 -00:02:02,350 --> 00:02:06,170 -method is a concrete implementation of this interface. - -41 -00:02:06,170 --> 00:02:10,630 -Finally, the Product is the object created by the factory method. So - -42 -00:02:10,630 --> 00:02:12,350 -summarizing, we have the interface for - -43 -00:02:12,350 --> 00:02:14,300 -the factory method, the actual implementation of - -44 -00:02:14,300 --> 00:02:17,540 -the summary method, and the object that is created by the factory method, - -45 -00:02:17,540 --> 00:02:21,020 -when it is invoked. So let's look at an example of this pattern. |