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  • Data scheme question

    - by Matt
    I am designing a data model for a local city page, more like requirements for it. So 4 tables: Country, State, City, neighbourhood. Real life relationships is: Country owns multiple State which owns multiple cities which ows multiple neighbourhoods. In the data model: Do we link these with FK the same way or link each with each? Like in each table there will even be a Country ID, State ID, CityID and NeighbourhoodID so each connected with each? Other wise to reach neighbourhood from country we need to join 2 other tables in between? There are more tables I need to maintain for IP addess of cities, latitude/longitude, etc.

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  • Is there a pattern that allows a constructor to be called only from a specific factory and from nowh

    - by willem
    We have a class, say LegacyUserSettingsService. LegacyUserSettingsService implements an interface, IUserSettingsService. You can get an instance of the IUserSettingsService by calling our ApplicationServicesFactory. The factory uses Spring.NET to construct the concrete LegacyUserSettingsService. The trouble is that new developers sometimes do their own thing and construct new instances of the LegacyUserSettingsService directly (instead of going via the factory). Is there a way to protect the constructor of the concrete class so it can only be called from the factory? A well-known pattern perhaps? Note that the concrete class resides in a different assembly (separate from the Factory's assembly, so the internal keyword is not a solution). The factory assembly references the other assembly that contains the concrete class. Any ideas?

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  • coco2d tab view for multi player

    - by godzilla
    I am currently developing a card game for the iphone using cocas2d. I am currently in need of a tab view with each tab representing a player and his / her set of cards. Currently i have a single view representing just one player. It seems as though cocas2s is not really built do have multiple views, to do this and it would require some serious amount of hacking around with the code. What would be the most efficient way to accomplish this?

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  • Search for a pattern in a list of strings - Python

    - by Holtz
    I have a list of strings containing filenames such as, file_names = ['filei.txt','filej.txt','filek.txt','file2i.txt','file2j.txt','file2k.txt','file3i.txt','file3j.txt','file3k.txt'] I then remove the .txt extension using: extension = os.path.commonprefix([n[::-1] for n in file_names])[::-1] file_names_strip = [n[:-len(extension)] for n in file_names] And then return the last character of each string in the list file_names_strip: h = [n[-1:] for n in file_names_strip] Which gives h = ['i', 'j', 'k', 'i', 'j', 'k', 'i', 'j', 'k'] How can i test for a pattern of strings in h? So if i,j,k occur sequentially it would return True and False if not. I need to know this because not all file names are formatted like they are in file_names. So: test_ijk_pattern(h) = True no_pattern = ['1','2','3','1','2','3','1','2','3'] test_ijk_pattern(no_pattern) = False

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  • Is there any danger in committing to a component library such as SmartGwt or Swing?

    - by Banang
    Since February this year I have been working on an app that's built using SmartGWT components. Generally, I find the components very nice to work with, and the fact that they're open source and free to use is just fantastic. However, I can't seem to shake the feeling that it's not a durable way of developing, but I can't quite explain why. Maybe it's because I know that any minute now the team developing it could decide to stop, which would leave me and my team in a bit of a pickle, but I'm sure there must be something more. I have been trying to find ways of explaining this feeling to myself, but to no avail. Therefore I turn to you, dear community, to ask if you can come up with a good reason why committing to building your app (that's supposed to be around for many more years to come) using a component library such as SmartGWT is a bad idea? Is there any reason I should just have developed the components myself? Or did I make the right choice when deciding not to reinvent the wheel and just go for what was readily available?

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  • When using a HiLo ID generation strategy, what types should be used to hold Ids?

    - by UpTheCreek
    I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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  • Desiging a AJAX website

    - by Narmatha Balasundaram
    What are the things to consider and watch out for when designing a website with AJAX? Must take care of conditions, say timeouts, error handling, for instance? Best practices? What parameters to take care of while designing and coding?

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  • What are the lengths/limits C preprocessor as a language creation tool? Where can I learn more about

    - by Weston C
    In his FAQ @ http://www2.research.att.com/~bs/bs_faq.html#bootstrapping, Bjarne Stroustrup says: To build [Cfront, the first C++ compiler], I first used C to write a "C with Classes"-to-C preprocessor. "C with Classes" was a C dialect that became the immediate ancestor to C++... I then wrote the first version of Cfront in "C with Classes". When I read this, it piqued my interest in the C preprocessor. I'd seen its macro capabilities as suitable for simplifying common expressions but hadn't thought about its ability to significantly add to syntax and semantics on the level that I imagine bringing classes to C took. So now I have a couple of questions on my mind: 1) Are there other examples of this approach to bootstrapping a language off of C? 2) Is the source to Stroustrup's original work available anywhere? 3) Where could I learn more about the specifics of utilizing this technique? 4) What are the lengths/limits of that approach? Could one, say, create a set of preprocessor macros that let someone write in something significantly Lisp/Scheme like?

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  • How to develop Online Shopping Portal Application using PHP ?

    - by Sarang
    I do not know PHP & I have to develop a Shopping Portal with following Definition : Scenario: Online Shopping Portal XYZ.com wants to create an online shopping portal for managing its registered customers and their shopping. The customers need to register themselves first before they do shopping using the shopping portal. However, everyone, whether registered or not, can view the various products along with the prices listed in the portal. The registered customers, after logging in, are allowed to place order for one or more products from the products listed in the portal. Once the order is placed, the customer gets a reference order number and the order status should be “order in process”. The customers can track their order using the given reference number. The management of XYZ.com should be able to modify the order status of a particular reference order number to “shipped” once the products are shipped to the shipping address entered by the customer at the time of placing the order. The Functionalities required are : Create the interface for the XYZ.com shopping portal using HTML/XHTML and CSS. Implement the client side validations using JavaScript. Create the tables using MySQL. Implement the functionality using the server side scripting language, PHP. Integrate all the above tasks and make the XYZ.com shopping portal functional. How do I develop this application with following proper steps of development ?

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  • internal implementation of database Queries

    - by harigm
    In my experience I have used many queries like select, order by, where clause etc.. in mysql, sql-server, oracle etc For a moment i have thought, 1)how is this internally written to implement the above queries 2) which language do they use? 3) is that programming language? if yes which language? 4)what kind of environment required to implement this kind of complex database

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  • What does ER_WARN_FIELD_RESOLVED mean?

    - by VolkerK
    When SHOW WARNINGS after a EXPLAIN EXTENDED shows a Note 1276 Field or reference 'test.foo.bar' of SELECT #2 was resolved in SELECT #1 what exactly does that mean and what impact does it have? In my case it prevents mysql from using what seems to be a perfectly good index. But it's not about fixing that specific query (as it is an irrelevant test). I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html butError: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED) Message: Field or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d isn't much of an explaination.

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  • some confusions to singleton pattern in PHP

    - by SpawnCxy
    Hi all, In my team I've been told to write resource class like this style: class MemcacheService { private static $instance = null; private function __construct() { } public static function getInstance($fortest = false) { if (self::$instance == null) { self::$instance = new Memcached(); if ($fortest) { self::$instance->addServer(MEMTEST_HOST, MEMTEST_PORT); } else { self::$instance->addServer(MEM_HOST, MEM_PORT); } } return self::$instance; } } But I think in PHP resource handles will be released and initialized again every time after a request over. That means MemcacheService::getInstance() is totally equal new Memcached() which cannot be called singleton pattern at all. Please correct me if I'm wrong. Regards

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  • Reducing a set of non-unique elements via transformations

    - by Andrey Fedorov
    I have: 1) a "starting set" of not-necessarily-unique elements, e.x. { x, y, z, z }, 2) a set of transformations, e.x. (x,z) = y, (z,z) = z, x = z, y = x, and 3) a "target set" that I am trying to get by applying transformations to the starting set, e.x. { z }. I'd like to find an algorithm to generate the (possibly infinite) possible applications of the transformations to the starting set that result in the target set. For example: { x, y, z, z }, y => x { x, x, z, z }, x => z { z, x, z, z }, x => z { z, z, z, z }, (z, z) => z { z, z, z }, (z, z) => z { z, z }, (z, z) => z { z } This sounds like something that's probably an existing (named) problem, but I don't recognize it. Can anyone help me track it down, or suggest further reading on something similar?

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  • Java - Calling all methods of a class

    - by Thomas Eschemann
    I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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  • Visitor Pattern can be replaced with Callback functions?

    - by getit
    Is there any significant benefit to using either technique? In case there are variations, the Visitor Pattern I mean is this: http://en.wikipedia.org/wiki/Visitor_pattern And below is an example of using a delegate to achieve the same effect (at least I think it is the same) Say there is a collection of nested elements: Schools contain Departments which contain Students Instead of using the Visitor pattern to perform something on each collection item, why not use a simple callback (Action delegate in C#) Say something like this class Department { List Students; } class School { List Departments; VisitStudents(Action<Student> actionDelegate) { foreach(var dep in this.Departments) { foreach(var stu in dep.Students) { actionDelegate(stu); } } } } School A = new School(); ...//populate collections A.Visit((student)=> { ...Do Something with student... }); *EDIT Example with delegate accepting multiple params Say I wanted to pass both the student and department, I could modify the Action definition like so: Action class School { List Departments; VisitStudents(Action<Student, Department> actionDelegate, Action<Department> d2) { foreach(var dep in this.Departments) { d2(dep); //This performs a different process. //Using Visitor pattern would avoid having to keep adding new delegates. //This looks like the main benefit so far foreach(var stu in dep.Students) { actionDelegate(stu, dep); } } } }

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  • How does one implement storage/retrieval of smart-search/mailbox features?

    - by humble_coder
    Hi All, I have a question regarding implementation of smart-search features. For example, consider something like "smart mailboxes" in various email applications. Let's assume you have your data (emails) stored in a database and, depending on the field for which the query will be created, you present different options to the end user. At the moment let's assume the Subject, Verb, Object approach… For instance, say you have the following: SUBJECTs: message, to_address, from_address, subject, date_received VERBs: contains, does_not_contain, is_equal_to, greater_than, less_than OBJECTs: ??????? Now, in case it isn't clear, I want a table structure (although I'm not opposed to an external XMLesque file of some sort) to store (and later retrieve/present) my criteria for smart searches/mailboxes for later use. As an example, using SVO I could easily store then reconstruct a query for "date between two dates" -- simply use "date greater than" AND "date less than". However, what if, in the same smart search, I wanted a "between" OR'ed with another criterion? You can see that it might get out of hand -- not necessarily in the query creation (as that is rather simplistic), but in the option presentation and storage mechanism. Perhaps I need to think more on a more granular level. Perhaps I need to simply allow the user to select AND or OR for each entry independently instead of making it an ALL OR NOTHING type smart search (i.e. instead of MATCH ALL or MATCH ANY, I need to simply allow them to select -- I just don't want it to turn into a Hydra). Any input would be most appreciated. My apologies if the question is a bit incoherent. It is late, and I my brain is toast. Best.

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  • what is the easiest way to do this function in c# ?

    - by From.ME.to.YOU
    Hello let say that we have an array [5,5] 01,02,03,04,05 06,07,08,09,10 11,12,13,14,15 16,17,18,19,20 21,22,23,24,25 the user should send 2 values to the function (start,searchFOR) for example (13,25) the function should search for that value in this way 07,08,09 12, ,14 17,18,19 if the value is n't found in this level it will goes a level higher 01,02,03,04,05 06, , , ,10 11, , , ,15 16, , , ,20 21,22,23,24,25 if the array is bigger than this and the value didn't found it will go to a level higher Thanks for your help

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  • Model a Zero or One to Many Relationship

    - by John
    How should I model a zero or one to a many relationship in the database? For example, a user record may or may not have a parent. So should my user table have a t_user.parent_id or should I have an associative table called t_user_hierarchy with the columns t_user_hierarchy.parent_id and t_user_hierarchy.user_id?

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  • Handling Dialogs in WPF with MVVM

    - by Ray Booysen
    In the MVVM pattern for WPF, handling dialogs is one of the more complex operations. As your view model does not know anything about the view, dialog communication can be interesting. I can expose an ICommand that when the view invokes it, a dialog can appear. Does anyone know of a good way to handle results from dialogs? I am speaking about windows dialogs such as MessageBox. One of the ways we did this was have an event on the viewmodel that the view would subscribe to when a dialog was required. public event EventHandler<MyDeleteArgs> RequiresDeleteDialog; This is OK, but it means that the view requires code which is something I would like to stay away from.

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  • C# Event Handlers Using an Enum

    - by Jimbo
    I have a StatusChanged event that is raised by my object when its status changes - however, the application needs to carry out additional actions based on what the new status is. e.g If the new status is Disconnected, then it must update the status bar text and send an email notification. So, I wanted to create an Enum with the possible statuses (Connected, Disconnected, ReceivingData, SendingData etc.) and have that sent with the EventArgs parameter of the event when it is raised (see below) Define the object: class ModemComm { public event CommanderEventHandler ModemCommEvent; public delegate void CommanderEventHandler(object source, ModemCommEventArgs e); public void Connect() { ModemCommEvent(this, new ModemCommEventArgs ModemCommEventArgs.eModemCommEvent.Connected)); } } Define the new EventArgs parameter: public class ModemCommEventArgs : EventArgs{ public enum eModemCommEvent { Idle, Connected, Disconnected, SendingData, ReceivingData } public eModemCommEvent eventType { get; set; } public string eventMessage { get; set; } public ModemCommEventArgs(eModemCommEvent eventType, string eventMessage) { this.eventMessage = eventMessage; this.eventType = eventType; } } I then create a handler for the event in the application: ModemComm comm = new ModemComm(); comm.ModemCommEvent += OnModemCommEvent; and private void OnModemCommEvent(object source, ModemCommEventArgs e) { } The problem is, I get a 'Object reference not set to an instance of an object' error when the object attempts to raise the event. Hoping someone can explain in n00b terms why and how to fix it :)

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  • How to restrict an access to some of the functions at third level in Classes (OOPs)

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? Class A { private A(){} protected A(int ){} } Class B : A {} CLass C:B { }

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