Lab:
Proxy Proxy Exercise Lab::
1) Simple Logging /Debugging Proxy: (from class)
Complete the simple proxy from class, which should be a proxy that just does a simple pre- and post- message. The steps are: a) Define a Main which should call
b) Define a class Thing, with a single compute() method. For now, just have the method print its single argument. c) Define a proxy pThing, which can proxy a Thing and gives a simple message both before and after the delegation to the actual proxy'ed subject (Thing) object.
d) Improve the design by encapsulating the pre and post actions (simple messages here) into their own methods in pThing.
2) Generalize using Functor: (Lab to do)
Make the proxy more general, by abstracting the pre/post methods from the proxy class, and using instead a functor argument to define them (dynamically). a) Define the Functor interface.
b) In main, instantiate a functor instance of a concrete functor, which replicates the behavior of just printing pre & post messages. c) Improve this by having the proxy also print the argument values for each proxy'ed method call.
d) Update Main to test this. 3) Generalize using Generics: (Lab to do) This proxy is general over methods, but specific on the (static) type of the arguments to the Thing.compute() method. Make it more general, by making both Thing and the proxy generic over this type. argument a) Make Thing generic over the argument type to its compute() method.
b) Convert pThing to also be generic over this type. c) Update Main to test this.
4) Generalize over different Subject types: (Next class! ...) To make the proxy more general, we would like to have it be able to proxy various subject types, not just Thing. This is hard, because an abstraction over the target type would mean somehow (automatically) having different wrapper methods in the proxy (each with appropriate names, and argument lists and types from the subject class), and inside of each the proper delegation code which would also have to be custom for each specific method (name and argument list and types) of the target class. None of the abstraction methods we have so far can do this. Classes abstract over structure, fu...