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• Finding databases for use in applications

  - by JonF

  Does anyone have some recommendations on how I can find databases for random things that I might want to use in my application. For example, a database of zip code locations, area code cities, car engines, IP address locations, or whatever. I'm just asking generally when you decide you need a bunch of data where are some good places to start looking other than google?

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• When is C++ covariance the best solution?

  - by Neil Butterworth

  This question was asked here a few hours ago and made me realise that I have never actually used covariant return types in my own code. For those not sure what covariance is, it's allowing the return type of (typically) virtual functions to differ provided the types are part of the same inheritance hierarchy. For example: struct A { virtual ~A(); virtual A * f(); ... }; struct B : public A { virtual B * f(); ... }; The different return types of the two f() functions are said to be covariant. Older versions of C++ required the return types to be the same, so B would have to look like: struct B : public A { virtual A * f(); ... }; So, my question: Does anyone have a real-world example where covariant return types of virtual functions are required, or produce a superior solution to simply returning a base pointer or reference?

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• using partials in view helpers

  - by takeshin

  Creating custom Zend View helpers I often end up with something like: // logic here if ($condition) { $output = <<<EOS... } else { $output = <<<EOS... } or using switch. Then to eliminate this, I create setPartial(), getPartial() and htmlize() for using external .phtml's. This is not the best solution, because partials do not support doctype changing. Is there any better solution, than creating abstract class handling this common case? Are there any ready Zend solutions for this case? Separate view helper for each case? And where to put common code?

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• what is "class A: public B < A >" this?

  - by Max

  What is the name of that kind of structure? Or where can I read about that. class A : public B < A { ... }

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• Implementing Tagging System with PHP and mySQL. Caching help!!!

  - by Hamid Sarfraz

  With reference to this post: http://stackoverflow.com/questions/2122546/how-to-implement-tag-counting I have implemented the suggested 3 table tagging system completely. To count the number of Articles per tag, i am using another column named tagArticleCount in the tag definition table. (other columns are tagId, tagText, tagUrl, tagArticleCount). If i implement realtime editing of this table, so that whenever user adds another tag to article or deletes an existing tag, the tag_definition_table is updated to update the counter of the added/removed tag. This will cost an extra query each time any modification is made. (at the same time, related link entry for tag and article is deleted from tagLinkTable). An alternative to this is not allowing any real time editing to the counter, instead use CRONs to update counter of each tag after a specified time period. Here comes the problem that i want to discuss. This can be seen as caching the article count in database. Can you please help me find a way to present the articles in a list when a tag is explored and when the article counter for that tag is not up to date. For example: 1. Counter shows 50 articles, but there are infact 55 entries in the tag link table (that links tags and articles). 2. Counter shows 50 articles, but there are infact 45 extries in the tag link table. How to handle these 2 scenerios given in example. I am going to use APC to keep cache of these counters. Consider it too in your solution. Also discuss performance in the realtime / CRONNED counter updates.

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• using ref to view error

  - by Avram

  Hello. I working now on firm that using ref in every function. The reason, is to catch errors. There example : //return true if the read is success //otherwise writing to the error ,the problem bool ReadFile(ref string error) Question: How do you catching errors? Using ref,exceptions or other way?

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• Best practice for debug Asserts during Unit testing

  - by Steve Steiner

  Does heavy use of unit tests discourage the use of debug asserts? It seems like a debug assert firing in the code under test implies the unit test shouldn't exist or the debug assert shouldn't exist. "There can be only one" seems like a reasonable principle. Is this the common practice? Or do you disable your debug asserts when unit testing, so they can be around for integration testing? Edit: I updated 'Assert' to debug assert to distinguish an assert in the code under test from the lines in the unit test that check state after the test has run. Also here is an example that I believe shows the dilema: A unit test passes invalid inputs for a protected function that asserts it's inputs are valid. Should the unit test not exist? It's not a public function. Perhaps checking the inputs would kill perf? Or should the assert not exist? The function is protected not private so it should be checking it's inputs for safety.

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• Are there any inherent benefits or drawbacks to choosing Google Code vs. SourceForge vs. Codeplex?

  - by kdmurray

  I've got a couple of different projects that I'd like to post up as open source. I've been trying to decide which of the three big open-source project hosting sites makes the most sense, or if I should just host it myself. Are there any inherent drawbacks or benefits to these three? Is there a "best" place to host a project? Do different sites make more sense for different kinds of projects?

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• package private static member class vs. package private class

  - by Helper Method

  I was writing two implementations of a linked list for an assignment, a doubly linked list and a circular doubly linked list. Now as the class representing a Link within the linked list is the same in both implementations, I want to use it in both. Now I wonder which approach would be better: Implement the Link class as a package private static member class in the first implementation and then use this class in the second implementation or make the Link class a package private class.

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• Is Embed Resource a good approach for a read only xml database?

  - by Nasser Hajloo

  I have an open source application (here) This application get a character or a sentence and give some unicode information about it. Iuse Unicode Character Database which provided by Unicode.org this is a XML document (130MB) At first I embed this XML to my DLL but I don't know is it a good approach or no. because DLL size growth just because of this XML document. I can use it like any other resources but usercan see it. What Should I do? What is the best pattern for this? and Why ? TIA

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• The Wheel Invention - Beneficial For Learning?

  - by Sarfraz

  Hello, Chris Coyier of css-tricks.com has written a good article titled Regarding Wheel Invention. In a paragraph he says: On the “reinventing” side, you benefit from complete control and learning from the process. And on the very next line he says: On the other side, you benefit from speed, reliability, and familiarity. Also often at odds are time spent and cost. He is right in both statements I think. I really like his first statement. I do actually sometimes re-invent the wheel to learn more and gain complete control over what I am inventing. I wonder why people are so much against that or rather biased. Isn't there the benefit of learning and getting complete control or probably some other benefits too. I would love to see what you have to say about this.

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• Searching for the right pattern to handle login data

  - by stevebot

  Hi all, I'm working on a controller that handles logins for a Web app. These logins will come from multiple clients but will all contain the same data. However, depending on the client, this data will be interpreted into common entities for our webapp differently. For instance, we have a user code that gets sent in, and in one case we may use the first four digits of the code, and in another case 12 digits of the code to map to a field on a User entity. Instead of handling this all in the controller and having big nasty if blocks of logic, I would like to use a pattern to handle how this information gets ingested into our application. What are your opinions?

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• how to make objects globally accessible?

  - by fayer

  i have this code: class IC_Core { /** * Database * @var IC_Database */ public static $db = NULL; /** * Core * @var IC_Core */ protected static $_instance = NULL; private function __construct() { } public static function getInstance() { if ( ! is_object(self::$_instance)) { self::$_instance = new self(); self::initialize(self::$_instance); } return self::$_instance; } private static function initialize(IC_Core $IC_Core) { self::$db = new IC_Database($IC_Core); } } but when i wanna access IC_Database with: $IC = IC_Core::getInstance(); $IC->db->add() // it says that its not an object. i think the problem lies in self::$db = new IC_Database($IC_Core); but i dont know how to make it work. could someone give me a hand=) thanks!

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• Arguments against Create or Update

  - by Nix

  Recently someone stated that they thought all Creates should be CreateOrUpdates. Instinctively i thought bad, but now I am trying to find out if I have any grounds. Situation interface IService{ void Create(Object a); void Update(Object a); } or interface IService{ void CreateOrUpdate(Object a); } My first thought is if you implemented everything CreateOrUpdate then you have no control if someone accidentally sends you wrong data, or concurrency issues where someone changes a "primary" field right before you call update.... But if you remove those cases, are there any other cons?

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• Simplest way to create a wrapper class around some strings for a WPF DataGrid?

  - by Joel

  I'm building a simple hex editor in C#, and I've decided to use each cell in a DataGrid to display a byte*. I know that DataGrid will take a list and display each object in the list as a row, and each of that object's properties as columns. I want to display rows of 16 bytes each, which will require a wrapper with 16 string properties. While doable, it's not the most elegant solution. Is there an easier way? I've already tried creating a wrapper around a public string array of size 16, but that doesn't seem to work. Thanks *The rational for this is that I can have spaces between each byte without having to strip them all out when I want to save my edited file. Also it seems like it'll be easier to label the rows and columns.

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• Using Remote Web Page to Initialize iPhone App

  - by Chris_K

  My iPhone app relies on a vendor's XML feed to provide data. But that feed is not locked down. The vendor could change the format of the XML at any time, although so far they've promised not to. Since I might want to tell my app to use a different URL for its data source, I'd like to set up a single "Command Central" Web page, on my own server, to direct the app to the correct data source. In other words, each time my app starts, in the background and unseen by the user, it would visit "http://www.myserver.com/iphoneapp_data_sources.xml" to retrieve the URL for retrieving data from my vendor. That way, if my vendor suddenly changes the exact URL or the XML feed that the app needs, I can update that Web page and ensure that all installations of the app are using the correct XML feed. Does anyone have any advice or examples showing this kind of approach? It seems as if this must be a common problem, but so far I haven't found a well-established design pattern that fits it.

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• Why is Visual Basic used?

  - by Arrieta

  I don't mean to start a holy war here, but I cannot fathom why would anybody use Visual Basic for a new project. Can you explain me why is it used? What new applications (which a lay person may be familiar with) have been developed in it? Why is it chosen over other languages? Thanks.

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• Subclassing and adding data members

  - by Marius

  I have an hierarchy of classes that looks like the following: class Critical { public: Critical(int a, int b) : m_a(a), m_b(b) { } virtual ~Critical() { } int GetA() { return m_a; } int GetB() { return m_b; } void SetA(int a) { m_a = a; } void SetB(int b) { m_b = b; } protected: int m_a; int m_b; }; class CriticalFlavor : public Critical { public: CriticalFlavor(int a, int b, int flavor) : Critical(a, b), m_flavor(flavor) { } virtual ~CriticalFlavor() { } int GetFlavor() { return m_flavor; } void SetFlavor(int flavor) { m_flavor = flavor; } protected: int m_flavor; }; class CriticalTwist : public Critical { public: CriticalTwist(int a, int b, int twist) : Critical(a, b), m_twist(twist) { } virtual ~CriticalTwist() { } int GetTwist() { return m_twist; } void SetTwist(int twist) { m_twist = twist; } protected: int m_twist; }; The above does not seem right to me in terms of the design and what bothers me the most is the fact that the addition of member variables seems to drive the interface of these classes (the real code that does the above is a little more complex but still embracing the same pattern). That will proliferate when in need for another "Critical" class that just adds some other property. Does this feel right to you? How could I refactor such code? An idea would be to have just a set of interfaces and use composition when it comes to the base object like the following: class Critical { public: virtual int GetA() = 0; virtual int GetB() = 0; virtual void SetA(int a) = 0; virtual void SetB(int b) = 0; }; class CriticalImpl { public: CriticalImpl(int a, int b) : m_a(a), m_b(b) { } ~CriticalImpl() { } int GetA() { return m_a; } int GetB() { return m_b; } void SetA(int a) { m_a = a; } void SetB(int b) { m_b = b; } private: int m_a; int m_b; }; class CriticalFlavor { public: virtual int GetFlavor() = 0; virtual void SetFlavor(int flavor) = 0; }; class CriticalFlavorImpl : public Critical, public CriticalFlavor { public: CriticalFlavorImpl(int a, int b, int flavor) : m_flavor(flavor), m_critical(new CriticalImpl(a, b)) { } ~CriticalFlavorImpl() { delete m_critical; } int GetFlavor() { return m_flavor; } void SetFlavor(int flavor) { m_flavor = flavor; } int GetA() { return m_critical-GetA(); } int GetB() { return m_critical-GetB(); } void SetA(int a) { m_critical-SetA(a); } void SetB(int b) { m_critical-SetB(b); } private: int m_flavor; CriticalImpl* m_critical; };

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• Validation - Data Integrity

  - by Thomas

  A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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• Implementing a live voting system

  - by Will Eddins

  I'm looking at implementing a live voting system on my website. The website provides a live stream, and I'd like to be able to prompt viewers to select an answer during a vote initiated by the caster. I can understand how to store the data in a mySQL database, and how to process the answers. However: How would I initially start the vote on the client-side and display it? Should a script be running every few seconds on the page, checking another page to see if a question is available for the user? Are there any existing examples of a real-time polling system such as what I'm looking at implementing?

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• Which pattern to use for logging? Dependency Injection or Service Locator?

  - by andlju

  Consider this scenario. I have some business logic that now and then will be required to write to a log. interface ILogger { void Log(string stuff); } interface IDependency { string GetInfo(); } class MyBusinessObject { private IDependency _dependency; public MyBusinessObject(IDependency dependency) { _dependency = dependency; } public string DoSomething(string input) { // Process input var info = _dependency.GetInfo(); var intermediateResult = PerformInterestingStuff(input, info); if (intermediateResult== "SomethingWeNeedToLog") { // How do I get to the ILogger-interface? } var result = PerformSomethingElse(intermediateResult); return result; } } How would you get the ILogger interface? I see two main possibilities; Pass it using Dependency Injection on the constructor. Get it via a singleton Service Locator. Which method would you prefer, and why? Or is there an even better pattern? Update: Note that I don't need to log ALL method calls. I only want to log a few (rare) events that may or may not occur within my method.

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• Building a life-critical System using Agile

  - by Ben Breen

  Looking at the general trend of comments in my question about Building an Aircraft using Agile, the biggest problem other than cost appears to be safety. Do people feel that it is not possible to build a safe system (or prove it is safe) using agile? Doesn’t all the iterative testing mitigate this? Is it likely that a piece of software developed using agile will never be as reliable as counterparts such as waterfall?

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• Protocol specification in XML

  - by Mathijs

  Is there a way to specify a packet-based protocol in XML, so (de)serialization can happen automatically? The context is as follows. I have a device that communicates through a serial port. It sends and receives a byte stream consisting of 'packets'. A packet is a collection of elementary data types and (sometimes) other packets. Some elements of packets are conditional; their inclusion depends on earlier elements. I have a C# application that communicates with this device. Naturally, I don't want to work on a byte-level throughout my application; I want to separate the protocol from my application code. Therefore I need to translate the byte stream to structures (classes). Currently I have implemented the protocol in C# by defining a class for each packet. These classes define the order and type of elements for each packet. Making class members conditional is difficult, so protocol information ends up in functions. I imagine XML that looks like this (note that my experience designing XML is limited): <packet> <field name="Author" type="int32" /> <field name="Nickname" type="bytes" size="4"> <condition type="range"> <field>Author</field> <min>3</min> <max>6</min> </condition> </field> </packet> .NET has something called a 'binary serializer', but I don't think that's what I'm looking for. Is there a way to separate protocol and code, even if packets 'include' other packets and have conditional elements?

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• Best practice- How to team-split a django project while still allowing code reusal

  - by Infinity

  I know this sounds kind of vague, but please let me explain- I'm starting work on a brand new project, it will have two main components: "ACME PRODUCT" (think Gmail, Meebo, etc), and "THE SITE" (help, information, marketing stuff, promotional landing pages, etc lots of marketing-induced cruft). So basically the url /acme/* will load stuff in the uber cool ajaxy application, and every other URI will load stuff in the other site. Problem: "THE SITE" component is out of my hands, and will be handled by a consultants team that will work closely with marketing, And I and my team will work solely on the ACME PRODUCT. Question: How to set up the django project in such a way that we can have: Seperate releases. (They can push new marketing pages and functionality without having to worry about the state of our code. Maybe even separate Subversion "projects") Minimize impact (on our product) of whatever flying-unicorns-hocus-pocus the other team codes into the site. Still allow some code reusal. My main concern is that the ACME product needs to be rock solid, and therefore needs to be somewhat isolated of whatever mistakes/code bloopers the consultants make in their marketing side of the site. How have you handled this? Any ideas? Thanks!

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• When NOT to use MVVM?

  - by Vitalij

  I have started using MVVM pattern recently. I have had several projects where I used it and with every new one, I start to see that it will fit great within that new project. And now I start to ask myself are there situation when it's better NOT to use MVVM. Or is it such a nice pattern which you can use anywhere? Could you please describe several scenarios where MVVM wouldn't be the best choice?

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