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• How to structure data... Sequential or Hierarchical?

  - by Ryan

  I'm going through the exercise of building a CMS that will organize a lot of the common documents that my employer generates each time we get a new sales order. Each new sales order gets a 5 digit number (12222,12223,122224, etc...) but internally we have applied a hierarchy to these numbers: + 121XX |--01 |--02 + 122XX |--22 |--23 |--24 In my table for sales orders, is it better to use the 5 digital number as an ID and populate up or would it be better to use the hierarchical structure that we use when referring to jobs in regular conversation? The only benefit to not populating sequentially seems to be formatting the data later on in my view, but that doesn't sound like a good enough reason to go through the extra work. Thanks

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• Aggregation, Association and Composition (examples of code given)

  - by Bukocen

  I have such a simple example: public class Order { private ArrayList<Product> orders = new ArrayList<Product>(); public void add(Product p) { orders.add(p); } } Is it aggregation or composition? I guess it's composition, because orders will be delated after delete of Order, right? Unfortunately it was a task and answer was different;/ Do you know why? second problem: public class Client extends Person { String adress = ""; Orders orders = new Orders(); public Client(String n, String sn) { name = n; surName = sn; } public String getAddress() { return adress; } public Orders getOrders() { return this.orders; } } Is it Association between Client and Orders? My teacher told me that this is association, but I was wondering why it's not a aggregation/composition - he told me that aggregation or composition occur only when one class contains few instances of different class - is that right? I guess not, because e.g. car contains ONE wheel and it's aggregation I guess? What type of relation is that and why? Greetings

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• What should layers in dotnet application ?

  - by haansi

  I am using layered architecture in dotnet (mostly I work on web projects). I am confuse what layers should I use ? I have small idea that there should be the following layers. user interface customer types (custom entities) business logic layer data access layer My purpose is sure quality of work and maximum re-usability of code. some one suggested to add common types layer in it. Please guide me what should be layers ? and in each layer what part should go ?

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• Need recommendation for a table structure

  - by yapiskan

  I have an entity which has 4 different types of property that could have only one value for each case which are boolean, decimal, string or text. I don't want to define the table with 4 boolean, decimal, nvarchar and ntext columns. What would you recommend to cover this case?

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• STLifying C++ classes

  - by shambulator

  I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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• Web UI prototyping tools

  - by AlexKelos

  Can anyone recomend me a simple web UI prototyping tool, so I could quicky prototype the look of a my web site. I have tried to use MS Visio for this, but found it very "user un-friendly". What I really need is to be able quicky sketch the layout of the page, put some links, images and buttons on in, play a little bit with a colors (CSS), and it would be great it this tool could support navigation between the pages - but it is not essential. I would rather consider a low-cost or an open-source solution, since I am not a web designer and not going to use that tool on a daily basis.

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• guarantee child records either in one table or another, but not both?

  - by user151841

  I have a table with two child tables. For each record in the parent table, I want one and only one record in one of the child tables -- not one in each, not none. How to I define that? Here's the backstory. Feel free to criticize this implementation, but please answer the question above, because this isn't the only time I've encountered it: I have a database that holds data pertaining to user surveys. It was originally designed with one authentication method for starting a survey. Since then, requirements have changed, and now there are two different ways someone could sign on to start a survey. Originally I captured the authentication token in a column in the survey table. Since requirements changed, there are three other bits of data that I want to capture in authentication. So for each record in the survey table, I'm either going to have one token, or a set of three. All four of these are of different types, so my thought was, instead of having four columns where either one is going to be null, or three are going to be null ( or even worse, a bad mashup of either of those scenarios ), I would have two child tables, one for holding the single authentication token, the other for holding the three. Problem is, I don't know offhand how to define that in DDL. I'm using MySQL, so maybe there's a feature that MySQL doesn't implement that lets me do this.

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• NoSQL vs Relational Coding Styles

  - by Chris Henry

  When building objects that make use of data stored in a RDBMS, it's normally pretty clear what you're getting back, as dictated by the tables and columns being queried. However, when dealing with NoSQL, document-based systems, it's less clear what is being retrieved. What are common methods of keeping track of structure in which data is stored?

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• What is the definition of a Service object ?

  - by Maskime

  I've been working a lot with PHP. But recently i was sent on a work wich use Java. In PHP i used to do a lot of Singleton object but this pattern has not the same signification in Java that it has in PHP. So i wanted to go for an utility class (a class with static method) but my chief doesn't like this kind of classes and ask me to go for services object. So my guess was that a service object is just a class with a constructor that implement some public methods... Am i right ?

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• Suggested improvements?

  - by J Harley

  Hello, I have been coding a site in pure HTML/CSS - using no server-side language. I was wondering if anyone had any feedback - is there anything that you would change etc...? Many Thanks, J View Site

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• What do I need to know before working on an IM application?

  - by John

  I'm looking into building an IM-type application using Java stack (for the server at least). I'd be interested to see any information/advice on how applications like Skype/AIM/MSN work, as well as know any technologies/APIs that might be relevant. Without giving away the idea itself, it's perhaps more akin to Google Wave than Skype, but information useful for either is very welcome. Specific points I have already thought of include: Server Vs P2P... for reasons of logging my system will require all communication to go through a central server. Is this how other IM tools work... especially when audio/video comes into the equation? Cross-communication with other systems. Are there APIs for this or do all IM providers work hard to keep their protocol secret? The nature of what I'm designing means integration could probably only be limited, but it definitely seems worthwhile from a business perspective

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• Constructors + Dependency Injection

  - by Sunny

  If I am writing up a class with more than 1 constructor parameter like: class A{ public A(Dependency1 d1, Dependency2 d2, ...){} } I usually create a "argument holder"-type of class like: class AArgs{ public Dependency1 d1 { get; private set; } public Dependency2 d2 { get; private set; } ... } and then: class A{ public A(AArgs args){} } Typically, using a DI-container I can configure the constructor for dependencies & resolve them & so there is minimum impact when the constructors need to change. Is this considered an anti-pattern and/or any arguments against doing this?

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• C++: Conceptual problem in designing an intepreter

  - by sub

  I'm programming an interpreter for an experimental programming language (educational, fun,...) So far, everything went well (Tokenizer & Parser), but I'm getting a huge problem with some of the data structures in the part that actually runs the tokenized and parsed code. My programming language basically has only two types, int and string, and they are represented as C++ strings (std class) and ints Here is a short version of the data structure that I use to pass values around: enum DataType { Null, Int, String } class Symbol { public: string identifier; DataType type; string stringValue; int intValue; } I can't use union because string doesn't allow me to. This structure above is beginning to give me a headache. I have to scatter code like this everywhere in order to make it work, it is beginning to grow unmaintainable: if( mySymbol.type == Int ) { mySymbol.intValue = 1234; } else { mySymbol.stringValue = "abcde"; } I use the Symbol data structure for variables, return values for functions and general representation of values in the programming language. Is there any better way to solve this? I hope so!

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• Running a sharded DB from a single machine

  - by ming yeow

  This sounds kinda dumb, but I have a sharded DB that I no longer think I need to run on 2 machines, and would like to run on one single machine instead. Any ideas on how that can potentially be done? There are lots of resources on how i can achieve the converse, but very little on how this can be done

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• Static and default constuctor

  - by Ram

  A non static class can have static as well as default constructor at the same time. What is the difference between these two constructors? When shall I go for only static or static with default constructor?

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• Makefile: expand dependencies

  - by Danyel

  First off, the title is very generic because there are just tons of ways of how to possibly solve this. However, I'm looking for a clean and neat way. Situation: I have two equal object files foo.o and foo-pi.o, the latter of which is position-independent (compiled with -fPIC). Both depend on foo.h and bar.h. Problem: How do I, without code duplication, declare dependency of all foo*.o to bar.h? Solutions so far: $(shell bash -c 'echo -ne foo{-pi,}.o'}: bar.h $(addsuffix .o, $(addprefix fo, o-pi o)): bar.h The first solution is not portable on systems that don't support bash, the second is a dirty solution since I could not figure out how to use empty strings in addprefix.

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• Why use sinlgeton instead of static class?

  - by Jouke van der Maas

  When would a singleton actually be easier or better than a static class? It seems to me creating a singleton is just extra effort that's not actually needed, but I'm sure there is a good reason. Otherwise, they wouldn't be used, obviously.

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• Need a field / flag / status number for mutliple use ?

  - by Jules

  I want to create a field in my database which will be easy to query. I think if I give a bit of background this will make more sense. My table has listings shown on my website. I run a program which looks at the listings a decides whether to hide them from being shown on the site. I also hide listings manually for various reasons. I want to store these reasons in a field, so more than one reason could be made for hiding. So I need some form of logic to determine which reasons have been used. Can anyone offer me any guidance on what will be future-proof aka new reasons and what will be quick and easy to query upon ?

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• Sharing class member data between sub components

  - by Tim Gradwell

  I have an aggregate 'main' class which contains some data which I wish to share. The main class also has other class members. I want to share the data with these other class members. What is the correct / neatest way to do this? The specific example I have is as follows. The main class is a .net Form. I have some controls (actually controls within controls) on the main form which need access to the shared data. Main Form - DataX - DataY - Control1 -- Subcontrol1 - Control2 -- SubControl2 SubControls 1 and 2 both wish to access DataX and DataY. The trouble is, I feel like better practice (to reduce coupling), would be that either subcontrols should not know about Main Form, or Main Form should not know about subcontrols - probably the former. For subcontrols not to know about Main Form, would probably mean Main Form passing references to both Controls 1 and 2, which in turn would pass the references on to SubControls 1 and 2. Lots of lines of code which just forward the references. If I later added DataZ and DataW, and Controls 3 and 4 and SubControls 3 and 4, I'd have to add lots more reference forwarding code. It seems simpler to me to give SubControls 1 and 2 member references to Main Form. That way, any sub control could just ask for MainForm.DataX or MainForm.DataY and if I ever added new data, I could just access it directly from the sub controls with no hassle. But it still involves setting the 'MainForm' member references every time I add a new Control or Subcontrol. And it gives me a gut feeling of 'wrong'. As you might be able to tell I'm not happy with either of my solutions. Is there a better way? Thanks

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• Interpreted languages: The higher-level the faster?

  - by immersion

  I have designed around 5 experimental languages and interpreters for them so far, for education, as a hobby and for fun. One thing I noticed: The assembly-like language featuring only subroutines and conditional jumps as structures was much slower than the high-level language featuring if, while and so on. I developed them both simultaneously and both were interpreted languages. I wrote the interpreters in C++ and I tried to optimize the code-execution part to be as fast as possible. My hypothesis: In almost all cases, performance of interpreted languages rises with their level (high/low). Am I basically right with this? (If not, why?)

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• Why Is Java Missing Access Specifiers?

  - by Tom Tresansky

  Does anyone understand why Java is missing: An access specifier which allows access by the class and all subclasses, but NOT by other classes in the same package? (Protected-minus) An access specifier which allows access by the class, all classes in the same package, AND all classes in any sub-package? (Default-plus) An access specifier which adds classes in sub-packages to the entities currently allowed access by protected? (Protected-plus) I wish I had more choices than protected and default. In particular, I'm interested in the Protected-plus option. Say I want to use a Builder/Factory patterned class to produce an object with many links to other objects. The constructors on the objects are all default, because I want to force you to use the factory class to produce instances, in order to make sure the linking is done correctly. I want to group the factories in a sub-package to keep them all together and distinct from the objects they are instantiating---this just seems like a cleaner package structure to me. No can do, currently. I have to put the builders in the same package as the objects they are constructing, in order to gain the access to defaults. But separating project.area.objects from project.area.objects.builders would be so nice. So why is Java lacking these options? And, is there anyway to fake it?

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• Is there any point to an interface if only one class implements it?

  - by user343587

  Looking at the (mature) codebase at my new job, there is an interface, and only one class implements it (as far as I can tell). Can/should I get rid of the interface?

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• How to implement the disposable pattern in a class that inherits from another disposable class?

  - by TheRHCP

  Hi, I often used the disposable pattern in simple classes that referenced small amount of resources, but I never had to implement this pattern on a class that inherits from another disposable class and I am starting to be a bit confused in how to free the whole resources. I start with a little sample code: public class Tracer : IDisposable { bool disposed; FileStream fileStream; public Tracer() { //Some fileStream initialization } public void Dispose() { this.Dispose(true); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!disposed) { if (disposing) { if (fileStream != null) { fileStream.Dispose(); } } disposed = true; } } } public class ServiceWrapper : Tracer { bool disposed; ServiceHost serviceHost; //Some properties public ServiceWrapper () { //Some serviceHost initialization } //protected override void Dispose(bool disposing) //{ // if (!disposed) // { // if (disposing) // { // if (serviceHost != null) // { // serviceHost.Close(); // } // } // disposed = true; // } //} } My real question is: how to implement the disposable pattern inside my ServiceWrapper class to be sure that when I will dispose an instance of it, it will dispose resources in both inherited and base class? Thanks.

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• Avoiding repetition with libraries that use a setup + execute model

  - by lijie

  Some libraries offer the ability to separate setup and execution, esp if the setup portion has undesirable characteristics such as unbounded latency. If the program needs to have this reflected in its structure, then it is natural to have: void setupXXX(...); // which calls the setup stuff void doXXX(...); // which calls the execute stuff The problem with this is that the structure of setupXXX and doXXX is going to be quite similar (at least textually -- control flow will prob be more complex in doXXX). Wondering if there are any ways to avoid this. Example: Let's say we're doing signal processing: filtering with a known kernel in the frequency domain. so, setupXXX and doXXX would probably be something like... void doFilter(FilterStuff *c) { for (int i = 0; i < c->N; ++i) { doFFT(c->x[i], c->fft_forward_setup, c->tmp); doMultiplyVector(c->tmp, c->filter); doFFT(c->tmp, c->fft_inverse_setup, c->x[i]); } } void setupFilter(FilterStuff *c) { setupFFT(..., &(c->fft_forward_setup)); // assign the kernel to c->filter ... setupFFT(..., &(c->fft_inverse_setup)); }

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• declare field without initial value in php?

  - by Charles

  I don't want to give an initial value. I want to set these later using the set method class Duck { var int id; var set = Array(); } Any idea how to declare without getting error?

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