Effective Java, along with other sources suggest that we should consider using composition over inheritance. I have often found my self achieving such composition by using the Decorator pattern and implementing forwarding methods that delegate invocations to a wrapped object. However, I often find myself writing many simple forwarding ...
I've been given this question in a tutorial, and I really don't know how to go about it. How must g and h be defined in terms of p and f in order to ensure that filter p . map f = map g . filter h always holds? Any pointers in the right direction would be greatly appreciated. ...
Is double-buffering still required when Desktop Composition is enabled? In Microsoft's Application Compatibility Guide: Graphical Device Interface (GDI) Prior to Windows Vista and Windows Server 2008, a window handle (HWND) was painted directly to the screen, which had certain benefits, but limited how Windows could di...
Hi everyone, To help gather a sense of Objective-C I'm creating a very basic connect 4 game sans Cocoa. In my program I have three modules: "Game": Contains an array that holds the board information. Object that is created within main, and is responsible for turns. Player and Computer objects live within this module. "Player"...
What is the difference between different types of association i.e. aggregation, composition and dependency? explain with the help of code examples(in java, C++ or pseudo code). ...
So I've spent some time thinking about this and been all over google looking for a 'solution' (the solution is most likely a matter of preference, but I'm unsure about this). Below is the problem I have, but the problem can be applied to a lot of situations regarding composition. I have a class, Colour, containing the members of red, gr...
The problem I have been given says this: In a similar way to mapMaybe, define the function: composeMaybe :: (a->Maybe b) -> (b -> Maybe c) -> (a-> Maybe c) which composes two error-raising functions. The type Maybe a and the function mapMaybe are coded like this: data Maybe a = Nothing | Just a mapMaybe g Nothing...
Hello, First of all, I do not want to extend a class. I would ideally like to do this. public function __construct() { /* Set Framework Variable */ global $Five; $this =& $Five; } I have a system where the variable $Five is a container class which contains other libraries. I could assign this to a local variable of Five... i.e. p...
Assuming: the path of file f is ~/f "which f" shows "~/f", Then, which f | cat shows ~/f. So cat here is applied to the quotation of ~/f, which is different with cat ~/f. My question is: how I could use one command composed of which and cat to achieve the result of cat ~/f? When I don't know the result of which f in advance, using ...
Hi, Is there any difference in terms of implementation as how a composition design can be different from delegation. For example the code below seems to be doing delegation since the user cannot access the composed object (i.e "a") without using b. Hence, the user would need to invoke interfaces of class b and then "class b" invoke appr...
class Room{ public: void ColorRoom(){}; }; class House{ public: Room* GetRoom(){return &m_room;} private: Room m_room; }; 1) Room cannot exist without a house, an house "has a" room. (composition) 2) Another way to color room would be to have a method in House that would invoke the ColorRoom in Room method but then t...
I would like to create compositions of workflows in WF (3.5). Is it possible to directly use a workflow as an activity inside another workflow? I don't want to use the InvokeWorkFlowActivity, since it executes the workflow asynchronously. ...
An example explains it best : public interface IA { void foo(); void bar(); } public class A : IA { public virtual void foo(){ Console.Write("foo"); bar(); //call virtual method } public virtual void bar(){ Console.Write("foo"); bar(); } } public class Interceptor : IInterceptor { public...
I have a class Parameter, the purpose of which is to represent the possible values a certain parameter could hold (implements two key methods, GetNumValues() and GetValue(int index)). Often one logical parameter (parameter values are bit flags) is best represented by 2 or more instances of the Parameter class (i.e. a Parameter that can ...
I am starting development on a new web application which uses JSF 2 as the view technology. I have no prior experience with JSF and am a bit confused about the concepts. I read some documentation on JSF and the main idea was that it a component based framework. Applications are built from components. But now there are two ways of crea...
In Scala, I've seen the constructs trait T extends S and trait T { this: S => used to achieve similar things (namely that the abstract methods in S must be defined before an instance may be created). What's the difference between them? Why would you use one over the other? ...
Composition and inheritance. I am aware that they are both tools to be chosen when appropriate, and context is very important in choosing between composition and inheritance. However, the discussion about the appropriate context for each is usually a little fuzzy; this has me beginning to consider just how distinctly inheritance and po...
Let's say I have an arbitray list of A class A { string K {get;set;} string V {get;set;} } ... List<A> theList = ... Is there an easy way to compose a dictionary from theList? (something like the following) Dictionary<string, string> dict = magic(x => x.K, x => x.V, theList) I don't want to write the following code: var d = new D...
Hello! Please let me know what is the best way to determine composition of young generation memory promoted to old generation, after each young GC event? Ideally I would like to know class names which are responsible say, for 80% of heap in each "young gen -> old gen" promotion chunk; Example: I have 600M young gen, each tenure promo...
Let's say that I have class, that uses some functionality of dict. I used to composite a dict object inside and provide some access from the outside, but recently thought about simply inheriting dict and adding some attributes and methods that I might require. Is it a good way to go, or should I stick to composition? ...