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What is the difference between aggregation, composition and dependency? [duplicate]

What is the difference between aggregation, composition and dependency?

Component based game engine design [closed]

I have been looking at game engine design (specifically focused on 2d game engines, but also applicable to 3d games), and am interested in some information on how to go about it. I have heard that many engines are moving to a component based design nowadays rather than the traditional deep-object hierarchy.

Do you know of any good links with information on how these sorts of designs are often implemented? I have seen evolve your hierarchy, but I can't really find many more with detailed information (most of them just seem to say "use components rather than a hierarchy" but I have found that it takes a bit of effort to switch my thinking between the two models).

Any good links or information on this would be appreciated, and even books, although links and detailed answers here would be preferred.

Software Design vs. Software Architecture [closed]

Could someone explain the difference between Software Design and Software Architecture?

More specifically; if you tell someone to present you the 'design' - what would you expect them to present? Same goes for 'architecture'.

My current understanding is:

• Design: UML diagram/flow chart/simple wireframes (for UI) for a specific module/part of the system
• Architecture: component diagram (showing how the different modules of the system communicates with each other and other systems), what language is to be used, patterns...?

Correct me if I'm wrong. I have referred Wikipedia has articles on http://en.wikipedia.org/wiki/Software_design and http://en.wikipedia.org/wiki/Software_architecture, but I'm not sure if I have understood them correctly.

RESTful URL design for search

I'm looking for a reasonable way to represent searches as a RESTful URLs.

The setup: I have two models, Cars and Garages, where Cars can be in Garages. So my urls look like:

/car/xxxx
  xxx == car id
  returns car with given id

/garage/yyy
  yyy = garage id
  returns garage with given id

A Car can exist on its own (hence the /car), or it can exist in a garage. What's the right way to represent, say, all the cars in a given garage? Something like:

/garage/yyy/cars     ?

How about the union of cars in garage yyy and zzz?

What's the right way to represent a search for cars with certain attributes? Say: show me all blue sedans with 4 doors :

/car/search?color=blue&type=sedan&doors=4

or should it be /cars instead?

The use of "search" seems inappropriate there - what's a better way / term? Should it just be:

/cars/?color=blue&type=sedan&doors=4

Should the search parameters be part of the PATHINFO or QUERYSTRING?

In short, I'm looking for a good guide/tutorial for cross-model REST url design, and for search.

[Update] I like Justin's answer, but he doesn't cover the multi-field search case:

/cars/color:blue/type:sedan/doors:4

or something like that. How do we go from

/cars/color/blue

to the multiple field case?

Large-scale design in Haskell?

What is a good way to design/structure large functional programs, especially in Haskell?

I've been through a bunch of the tutorials (Write Yourself a Scheme being my favorite, with Real World Haskell a close second) - but most of the programs are relatively small, and single-purpose. Additionally, I don't consider some of them to be particularly elegant (for example, the vast lookup tables in WYAS).

I'm now wanting to write larger programs, with more moving parts - acquiring data from a variety of different sources, cleaning it, processing it in various ways, displaying it in user interfaces, persisting it, communicating over networks, etc. How could one best structure such code to be legible, maintainable, and adaptable to changing requirements?

There is quite a large literature addressing these questions for large object-oriented imperative programs. Ideas like MVC, design patterns, etc. are decent prescriptions for realizing broad goals like separation of concerns and reusability in an OO style. Additionally, newer imperative languages lend themselves to a 'design as you grow' style of refactoring to which, in my novice opinion, Haskell appears less well-suited.

Is there an equivalent literature for Haskell? How is the zoo of exotic control structures available in functional programming (monads, arrows, applicative, etc.) best employed for this purpose? What best practices could you recommend?

Thanks!

EDIT (this is a follow-up to Don Stewart's answer):

@dons mentioned: "Monads capture key architectural designs in types."

I guess my question is: how should one think about key architectural designs in a pure functional language?

Consider the example of several data streams, and several processing steps. I can write modular parsers for the data streams to a set of data structures, and I can implement each processing step as a pure function. The processing steps required for one piece of data will depend on its value and others'. Some of the steps should be followed by side-effects like GUI updates or database queries.

What's the 'Right' way to tie the data and the parsing steps in a nice way? One could write a big function which does the right thing for the various data types. Or one could use a monad to keep track of what's been processed so far and have each processing step get whatever it needs next from the monad state. Or one could write largely separate programs and send messages around (I don't much like this option).

The slides he linked have a Things we Need bullet: "Idioms for mapping design onto types/functions/classes/monads". What are the idioms? :)

How do I decide when to use Node.js? [closed]

I am new to this kind of stuff, but lately I've been hearing a lot about how good Node.js is. Considering how much I love working with jQuery and JavaScript in general, I can't help but wonder how to decide when to use Node.js. The web application I have in mind is something like Bitly - takes some content, archives it.

From all the homework I have been doing in the last few days, I obtained the following information. Node.js

• is a command-line tool that can be run as a regular web server and lets one run JavaScript programs
• utilizes the great V8 JavaScript engine
• is very good when you need to do several things at the same time
• is event-based so all the wonderful Ajax-like stuff can be done on the server side
• lets us share code between the browser and the backend
• lets us talk with MySQL

Some of the sources that I have come across are:

• Diving into Node.js – Introduction and Installation
• Understanding NodeJS
• Node by Example
• Let’s Make a Web App: NodePad

Considering that Node.js can be run almost out-of-the-box on Amazon's EC2 instances, I am trying to understand what type of problems require Node.js as opposed to any of the mighty kings out there like PHP, Python and Ruby. I understand that it really depends on the expertise one has on a language, but my question falls more into the general category of: When to use a particular framework and what type of problems is it particularly suited for?

Mutable vs immutable objects

I'm trying to get my head around mutable vs immutable objects. Using mutable objects gets a lot of bad press (e.g. returning an array of strings from a method) but I'm having trouble understanding what the negative impacts are of this. What are the best practices around using mutable objects? Should you avoid them whenever possible?

Who architected / designed C++'s IOStreams, and would it still be considered well-designed by today's standards?

First off, it may seem that I'm asking for subjective opinions, but that's not what I'm after. I'd love to hear some well-grounded arguments on this topic.

In the hope of getting some insight into how a modern streams / serialization framework ought to be designed, I recently got myself a copy of the book Standard C++ IOStreams and Locales by Angelika Langer and Klaus Kreft. I figured that if IOStreams wasn't well-designed, it wouldn't have made it into the C++ standard library in the first place.

After having read various parts of this book, I am starting to have doubts if IOStreams can compare to e.g. the STL from an overall architectural point-of-view. Read e.g. this interview with Alexander Stepanov (the STL's "inventor") to learn about some design decisions that went into the STL.

What surprises me in particular:

• It seems to be unknown who was responsible for IOStreams' overall design (I'd love to read some background information about this — does anyone know good resources?);

• Once you delve beneath the immediate surface of IOStreams, e.g. if you want to extend IOStreams with your own classes, you get to an interface with fairly cryptic and confusing member function names, e.g. getloc/imbue, uflow/underflow, snextc/sbumpc/sgetc/sgetn, pbase/pptr/epptr (and there's probably even worse examples). This makes it so much harder to understand the overall design and how the single parts co-operate. Even the book I mentioned above doesn't help that much (IMHO).

Thus my question:

If you had to judge by today's software engineering standards (if there actually is any general agreement on these), would C++'s IOStreams still be considered well-designed? (I wouldn't want to improve my software design skills from something that's generally considered outdated.)

prototype based vs. class based inheritance

In JavaScript, every object is at the same time an instance and a class. To do inheritance, you can use any object instance as a prototype.

In Python, C++, etc.. there are classes, and instances, as separate concepts. In order to do inheritance, you have to use the base class to create a new class, which can then be used to produce derived instances.

Why did JavaScript go in this direction (prototype-based object orientation)? what are the advantages (and disadvantages) of prototype-based OO with respect to traditional, class-based OO?

Are there free iPhone navigation bar icon sets available?

I want to use up/down icons like the ones used by "mail" in the upper-right corner when you're viewing a specific message. Are these icons available for free anywhere?

Beyond that, are there any sites with free navigation bar, toolbar, or tab bar icons?

Thank you!

Struct like objects in Java

Is it completely against the Java way to create struct like objects?

class SomeData1 {
    public int x;
    public int y;
}

I can see a class with accessors and mutators being more Java like.

class SomeData2 {
    int getX();
    void setX(int x);

    int getY();
    void setY(int y);

    private int x;
    private int y;
}

The class from the first example is notationally convenient.

// a function in a class
public int f(SomeData1 d) {
    return (3 * d.x) / d.y;
}

This is not as convenient.

// a function in a class
public int f(SomeData2 d) {
    return (3 * d.getX()) / d.getY();
}

What program should I use to mock up GUIs? [closed]

I want to mockup a GUI system so that I can figure out how best to represent what I need. Normally, I would design a GUI in something like glade and then write a quick mockup in Python which implements only the GUI logic (ie, making menus/sub windows etc appear) and not business logic.

Are there any tools which automate this?

I mean, I can use glade or Visual Studio or whatever to draw a GUI and then write some code to glue things together, but I wonder if there is some tool which would minimize (or eliminate) having to write code, so that I can get input for potential GUI designs from non-programmers too.

Ideally, it would let you do things like draw non-standard widgets and perhaps define simple behaviours to them (eg, draggable, or clickable or whatever).

How to inherit constructors?

Imagine a base class with many constructors and a virtual method

public class Foo
{
   ...
   public Foo() {...}
   public Foo(int i) {...}
   ...
   public virtual void SomethingElse() {...}
   ...
}

and now i want to create a descendant class that overrides the virtual method:

public class Bar : Foo 
{
   public override void SomethingElse() {...}
}

And another descendant that does some more stuff:

public class Bah : Bar
{
   public void DoMoreStuff() {...}
}

Do i really have to copy all constructors from Foo into Bar and Bah? And then if i change a constructor signature in Foo, do i have to update it in Bar and Bah?

Is there no way to inherit constructors? Is there no way to encourage code reuse?

How to design RESTful search/filtering?

I'm currently designing and implementing a RESTful API in PHP. However, I have been unsuccessful implementing my initial design.

GET /users # list of users
GET /user/1 # get user with id 1
POST /user # create new user
PUT /user/1 # modify user with id 1
DELETE /user/1 # delete user with id 1

So far pretty standard, right?

My problem is with the first one GET /users. I was considering sending parameters in the request body to filter the list. This is because I want to be able to specify complex filters without getting a super long url, like:

GET /users?parameter1=value1&parameter2=value2&parameter3=value3&parameter4=value4

Instead I wanted to have something like:

GET /users
# Request body:
{
    "parameter1": "value1",
    "parameter2": "value2",
    "parameter3": "value3",
    "parameter4": "value4"
}

which is much more readable and gives you great possibilities to set complex filters.

Anyway, file_get_contents('php://input') didn't return the request body for GET requests. I also tried http_get_request_body(), but the shared hosting that I'm using doesn't have pecl_http. Not sure it would have helped anyway.

I found this question and realized that GET probably isn't supposed to have a request body. It was a bit inconclusive, but they advised against it.

So now I'm not sure what to do. How do you design a RESTful search/filterng function?

I suppose I could use POST, but that doesn't seem very RESTful.

How do you design object oriented projects?

I'm working on a large project (for me) which will have many classes and will need to be extensible, but I'm not sure how to plan out my program and how the classes need to interact.

I took an OOD course a few semesters back and learned a lot from it; like writing UML, and translating requirements documents into objects and classes. We learned sequence diagrams too but somehow I missed the lecture or something, they didn't really stick with me.

With previous projects I've tried using methods I learned from the course but usually end up with code that as soon as I can say "yeah that looks something like what I had in mind" i have no desire to dig through the muck to add new features.

I've got a copy of Steve McConnell's Code Complete which I continually hear is amazing, here and elsewhere. I read the chapter on design and didn't seem to come out with the information I'm looking for. I know he says that it's not a cut and dried process, that it's mostly based on heuristics, but I can't seem to take all his information and apply it to my projects.

So what are things you do during the high level design phase (before you begin programming) to determine what are the classes you need (especially ones not based on any 'real world objects') and how will they interact with each other?

Specifically I'm interested in what are the methods you use? What is the process you follow that usually yeilds a good, clean design that will closely represent the final product?