Changes between Version 40 and Version 41 of PRO_LIB_CORE_TUTORIAL_NEW
- Timestamp:
- 07/02/09 20:27:00 (16 years ago)
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PRO_LIB_CORE_TUTORIAL_NEW
v40 v41 181 181 In order to create an AutoProperty, by convention you declare a method structure like the structure of the area() method which declares a local class which extends the AutoProperty class. The type argument of the local class should be identical to the type argument of the Prop which the area() method returns - after all an AutoProperty is a Property which computes a given value following some logic and that value has a type which in our case is Integer.[[BR]] 182 182 So you override the compute() method to provide the AutoProperty's value computation logic inside. You can provide an arbitrary complex logic inside. In this example whenever the width() and height() Properties change their value, the AutoProperty is smart enough to call the compute() method again and update its value.[[BR]] 183 183 '''Something very important:''' compute() will be recomputed only in the cases when some of the '''Properties''' used inside it change their value!! If compute() depends on some normal Java field, there's no way for the ProLib to know when this field has changed its value and then notify the AutoProperty to change its value!! '''There's no magic here!!''' Expecting the ProLib to detect that means hooking to JVM's system events and maybe bytecode instrumentation which obviously we don't want to use (: 184 184 * Actually, AutoProperties have a '''doSet()''' method, which can be overriden to provide setting manually a value of a given AutoProperty. This can be used in ''very rare cases'' when you have an AutoProperty X which depends on other Properties but also there's an AutoProperty Y which depends on X. So let's say that we need Y to have a valid value but at this stage of execution of our program we don't have all the Properties which X depends on initialized. That's when we can manually set the value of X, so Y gets property computed, and later, when all the Properties X depends on initialize, then X gets recomputed and Y respectively.[[BR]] 185 185 This should be used very rarely, so if you think you need this, consult first with someone else (:
