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  • Table in DB for generating primary keys?

    - by Sapphire
    Do you ever use a separate table for "generating" artificial primary keys for DB (and why)? What I mean is to have a table with two columns, table name and current ID - with which you could get new "ID" for some table by simply locking the row with that table name, getting the current value of the key, increment it by one, and unlock the row. Why would you prefer this over standard integer identity column? P.S. The "idea" is from Fowlers Patterns of Enterprise Application Architecture, btw...

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  • 3D Mesh Joining

    - by morlst
    I have 2 (or more) intersecting meshes, which require joining into 1 mesh object. I want to have some control over the resulting seam vertex insertion, so looking to write myself rather than use a library. Has anyone come across some open source code to base the algorithm on / ideas on the process? Initial impressions are: 1. Present in every 3D modelling program - mostly reinventing existing process (hence search for examples) 2. Potential for fiddly-ness around the polygon face direction and just touching conditions. (see above point)

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  • Where does the query language sit within the MVC pattern?

    - by weesilmania
    I'd assume that since the query language sits within the controller (typically) that it belongs to that component, but if I play devil's advocate I'd argue that the query language is execute within the domain of the model, and is tightly coupled to that component so it might also be a part of it. Anyone know the answer? Is there a straight answer or is it technology specific?

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  • Writing my own implementation of stl-like Iterator in C++.

    - by Negai
    Good evening everybody, I'm currently trying to understand the intrinsics of iterators in various languages i.e. the way they are implemented. For example, there is the following class exposing the list interface. template<class T> class List { public: virtual void Insert( int beforeIndex, const T item ) throw( ListException ) =0 ; virtual void Append( const T item ) =0; virtual T Get( int position ) const throw( ListException ) =0; virtual int GetLength() const =0; virtual void Remove( int position ) throw( ListException ) =0; virtual ~List() =0 {}; }; According to GoF, the best way to implement an iterator that can support different kinds of traversal is to create the base Iterator class (friend of List) with protected methods that can access List's members. The concrete implementations of Iterator will handle the job in different ways and access List's private and protected data through the base interface. From here forth things are getting confusing. Say, I have class LinkedList and ArrayList, both derived from List, and there are also corresponding iterators, each of the classes returns. How can I implement LinkedListIterator? I'm absolutely out of ideas. And what kind of data can the base iterator class retrieve from the List (which is a mere interface, while the implementations of all the derived classes differ significantly) ? Sorry for so much clutter. Thanks.

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  • does anyone see any issues with this thread pattern?

    - by prmatta
    Here is a simple thread pattern that I use when writing a class that needs just one thread, and needs to a specific task. The usual requirements for such a class are that it should be startable, stopable and restartable. Does anyone see any issues with this pattern that I use? public class MyThread implements Runnable { private boolean _exit = false; private Thread _thread = null; public void start () { if (_thread == null) { _thread = new Thread(this, "MyThread"); _thread.start(); } } public void run () { while (_exit) { //do something } } public void stop () { _exit = true; if (_thread != null) { _thread.interrupt(); _thread = null; } } } I am looking for comments around if I am missing something, or if there is a better way to write this.

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  • DDD: Where to create entity objects?

    - by ciscoheat
    I have three entities that must interact: User, SupportTicketand PhoneConversation. When someone calls in requesting help, the User should have a SupportTicket assigned to him, with a PhoneConversation assigned to the Ticked describing the call. My question is: In what entity should I put the method CreatePhoneSupportTicket() that creates a new SupportTicket and a PhoneConversation, relates them to each other and finally relates the SupportTicket to the User? I'm guessing it can't be on the user because that would violate the SRP (the user does a few more things). But the method itself does more than one thing, it should create both a SupportTicket and a PhoneConversation. Is this a situation when a Service is a better solution then putting methods on entities? Thanks for your help!

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  • Changes to data inside class not being shown when accessed from outside class.

    - by Hypatia
    I have two classes, Car and Person. Car has as one of its members an instance of Person, driver. I want to move a car, while keeping track of its location, and also move the driver inside the car and get its location. However, while this works from inside the class (I have printed out the values as they are calculated), when I try to access the data from main, there's nothing there. I.e. the array position[] ends up empty. I am wondering if there is something wrong with the way I have set up the classes -- could it be a problem of the scope of the object? I have tried simplifying the code so that I only give what is necessary. Hopefully that covers everything that you would need to see. The constructer Car() fills the offset array of driver with nonzero values. class Car{ public: Container(float=0,float=0,float=0); ~Container(); void move(float); void getPosition(float[]); void getDriverPosition(float[]); private: float position[3]; Person driver; float heading; float velocity; }; class Person{ public: Person(float=0,float=0,float=0); ~Person(); void setOffset(float=0,float=0,float=0); void setPosition(float=0,float=0,float=0); void getOffset(float[]); void getPosition(float[]); private: float position[3]; float offset[3]; }; Some of the functions: void Car::move(float time){ float distance = velocity*time; location[0] += distance*cos(PI/2 - heading); location[1] += distance*sin(PI/2 - heading); float driverLocation [3]; float offset[3]; driver->getOffset(offset); for (int i = 0; i < 3; i++){ driverLocation[i] = offset[i] + location[i]; } } void Car::getDriverPosition(float p[]){ driver.getPosition(p); } void Person::getPosition(float p[]){ for (int i = 0; i < 3; i++){ p[i] = position[i]; } } void Person::getOffset(float o[]){ for (int i = 0; i < 3; i++){ o[i] = offset[i]; } } In Main: Car * car = new Car(); car->move(); float p[3]; car->getDriverPosition(p); When I print driverLocation[] inside the move() function, I have actual nonzero values. When I print p[] inside main, all I get are zeros.

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  • When to use basic types (Integer, String), and when to write a new class?

    - by belgarat
    Stackoverflow users: A lot of things can be represented in programs by using the basic types, or we can create a new class for it. Example: A social security number can be a number, string or its own object. (Other common examples: Phone numbers, names, zip codes, user id, order id and other id's.) My question is: When should the basic types be used, and when should we write ourselves a new class? I see that when you need to add behavior, you'll want to create a class (example, social security number parsing, validation, formatting, etc). But is this the only criteria? I have come across cases where many of these things are represented as java Integers and/or Strings. We loose the benefit of type-checking, and I have often seen bugs caused by parameters being mixed in calls to function(Intever, Integer, Integer, Integer). On the other hand, some programmers are opposed to over-designing by creating classes for "eveything". Obviously, the answer is "it depends". But, what do you think, and what do you normally do?

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  • 4GB limitation on these embedded/express DBs good enough? what's next if limitation is reached?

    - by edwin.nathaniel
    I'm wondering how long a (theoretically) desktop-app can consume the full 4GB limitation of these express/embedded database products (SQL-Server Express, Oracle Express, SQLite3, etc) provided that big blobs will be stored in filesystem. Also what would be your strategy when it hits the 4GB? Archive the old DB Copy 1-3 months of data to the new DB (consider this as cache strategy?) Start using the new DB from this point onward (How do you access the old data?) I understand that the answer might varies depending on how much data you stored in the table/column. But please describe based on your experience (what kind of desktop-app, write/read heavy, how long will it reach according to your guess).

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  • Applet networking patterns

    - by Kristoffersen
    Hi SO. I have an applet that connects to a server, it receives some commands and based on that it haves to draw (or move) different things. Which patterns should I use? I assume that the network connection and applet should run in two different threads? Thanks, Kristoffer

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  • Game Objects Talking To Each Other

    - by PhilCK
    What is a good way of dealing with objects and having them talk to each other? Up until now all my games hobby/student have been small so this problem was generally solved in a rather ugly way, which lead to tight integration and circular dependencies. Which was fine for the size of projects I was doing. However my projects have been getting bigger in size and complexity and now I want to start re-using code, and making my head a simpler place. The main problem I have is generally along the lines of Player needs to know about the Map and so does the Enemy, this has usually descended into setting lots of pointers and having lots of dependencies, and this becomes a mess quickly. I have thought along the lines of a message style system. but I cant really see how this reduces the dependencies, as I would still be sending the pointers everywhere. Thanks. PS: I guess this has been discussed before, but I don't know what its called just the need I have.

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  • How to simplify the code?

    - by Tattat
    I have objectA, and objectB.... also I have objectAs, and objectBs. the objectA is only have the init method, and ObjectAs have somethings like this: #import "ObjectAs.h" @implementation ObjectAs @synthesize objectAs; -(id) init{ if( (self=[super init])) { self.objectAs = [[NSMutableArray alloc] init]; } return self; } -(int)getObjectAsNumber{ return [self.objectAs count]; } -(void)addObjectA:(ObjectA *)newObjectA{ [self.objectAs addObject:newObjectA]; } -(id)getObjectAByIdx:(int)objectAIdx{ return [self.objectAs objectAtIndex:objectAIdx]; } -(void)dealloc{ [super dealloc]; [objectAs release]; } @end The objectBs have similar have, I know that I can copy and paste, and replace it. Is there any way to simplify the objectBs, and objectAs? thz a lot.

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  • How important is it that models be consistent across project components?

    - by RonLugge
    I have a project with two components, a server-side component and a client-side component. For various reasons, the client-side device doesn't carry a fully copy of the database around. How important is it that my models have a 1:1 correlation between the two sides? And, to extend the question to my bigger concern, are there any time-bombs I'm going to run into down the line if they don't? I'm not talking about having different information on each side, but rather the way the information is encapsulated will vary. (Obviously, storage mechanisms will also vary) The server side will store each user, each review, each 'item' with seperate tables, and create links between them to gather data as necessary. The client side shouldn't have a complete user database, however, so rather than link against the user for gathering things like 'name', I'd store that on the review. In other words... --- Server Side --- Item: +id //Store stuff about the item User: +id +Name -Password Review: +id +itemId +rating +text +userId --- Device Side --- Item: +id +AverageRating Review: +id +rating +text +userId +name User: +id +Name //Stuff The basic idea is that certain 'critical' information gets moved one level 'up'. A user gets the list of 'items' relevant to their query, with certain review-orientation moved up (i. e. average rating). If they want more info, they query the detail view for the item, and the actual reviews get queried and added to the dataset (and displayed). If they query the actual review, the review gets queried and they pick up some additional user info along the way (maybe; I'm not sure if the user would have any use for any of the additional user information). My basic concern is that I don't wan't to glut the user's bandwidth or local storage with a huge variety of information that they just don't need, even if proper database normalizations suggests that information REALLY should be stored at a 'lower' level. I've phrased this as a fairly low-level conceptual issue because that's the level I'm trying to think / worry over, but if it matters I'm creating a PHP / MySQL server that provides data for a iOS / CoreData client.

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  • Web UI element to represent two different micro-views of data in the same spot?

    - by Chris McCall
    I've been tasked with laying out a portion of a screen for a customer care (call center) app that serves as sort of a header/summary block at the top of the screen. Here's what it looks like: The important part is in the red box. That little tooltip is the biz's vision for how to represent both the numeric SiteId and the textual Site Name all in the same piece of screen real estate. I asked, and the business thinks the Name is more important than the ID, but lists the Id by default, because the Name can't be truncated in the display, and there's only so much horizontal room to put the data. So they go with the Id, because it's fewer characters, and then they have the user mouse-over the Id to display the name (presumably because the tooltip can be of unlimited width and since it's floating over the rest of the screen, the full name will always be displayed. So, here's my question: Is there some better UI metaphor that I don't know about that could get this job done, while meeting the following constraints?: Does not require the mouse (uses a keyboard shortcut to do the "reveal") Allows the user to copy and paste the name Will not truncate the name Provides for the display of both the ID and name in the same spot Works with IE7

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  • Mocking a namespace in a partial class.

    - by Nix
    I am messing around with Entity Framework 3.5 SP1 and I am trying to find a cleaner way to do the below. Basically I have an EF model and I am adding some Eager Loaded entities and i want to put them in the partial class context Eager namespace. Currently I am using composition but I feel like there is an easier way to do what I want. namespace Entities{ public partial class TestObjectContext { EagerExtensions Eager { get;set;} public TestObjectContext(){ Eager = new EagerExtensions (this); } } public partial class EagerExtensions { TestObjectContext context; public EagerExtensions(TestObjectContext _context){ context = _context; } public IQueryable<TestEntity> TestEntity { get { return context.TestEntity .Include("TestEntityType") .Include("Test.Attached.AttachedType") .AsQueryable(); } } } } public class Tester{ public void ShowHowIWantIt(){ TestObjectContext context= new TestObjectContext(); var query = from a in context.Eager.TestEntity select a; } }

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  • How to handle product ratings in a database

    - by Mel
    Hello, I would like to know what is the best approach to storing product ratings in a database. I have in mind the following two (simplified, and assuming a MySQL db) scenarios: Scenario 1: Create two columns in the product table to store number of votes and the sum of all votes. Use columns to get an average on the product display page: products(productedID, productName, voteCount, voteSum) Pros: I will only need to access one table, and thus execute one query to display product data and ratings. Cons: Write operations will be executed in a table whose original purpose is only to furnish product data. Scenario 2: Create an additional table to store ratings. products(productID, productName) ratings(productID, voteCount, voteSum) Pros: Isolate ratings into a separate table, leaving the products table to furnish data on available products. Cons: I will have to execute two separate queries on product page requests (one for data and another for ratings). In terms of performance, which of the following two approaches is best: Allow users to execute an occasional write query to a table that will handle hundreds of read requests? Execute two queries at every product page, but isolate the write query into a separate table. I'm a novice to database development, and often find myself struggling with simple questions such as these. Many thanks,

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  • Tags php improving database speed and user experience

    - by Doodle
    How did stackOverFlow, excuse me if it wasn't the first implementation of this system. Decide what its initial tags where? I want to provide users with the best experience on my site and am implementing a tags system. I don't care about search engines or any of that. I just care about my users. Does any one have any advice about things that have failed or succeeded when they allowed users to tag things? Does any one know some good resources about the methodologies of user tagging? Does any one know some good resources about implementing a tags system from a programming perspective, database structures, theories, etc ? I'll give my check to who ever I feel points me in the best direction on the subject.

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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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  • what is main focus for a developer when coding?

    - by ajsie
    i read a lot of books about how to code right and usually the are talking about all these techniques from a point of view i can't understand. eg. lets consider the singleton pattern. i'm restricting so the class can only be instantiated once. but since it's only me creating the application, if i know that the class only should be instantiated once, then why would i create it a second time? i feel like missing the big picture. what is my main goal when coding an application? how should i think? thanks

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  • What's the best way to handle modules that use each other?

    - by Axeman
    What's the best way to handle modules that use each other? Let's say I have a module which has functions for hashes: # Really::Useful::Functions::On::Hash.pm use base qw<Exporter>; use strict; use warnings; use Really::Useful::Functions::On::List qw<transform_list>; our @EXPORT_OK = qw<transform_hash transform_hash_as_list ...>; #... sub transform_hash { ... } #... sub transform_hash_as_list { return transform_list( %{ shift() } ); } #... 1 And another module has been segmented out for lists: # Really::Useful::Functions::On::List.pm use base qw<Exporter>; use strict; use warnings; use Really::Useful::Functions::On::Hash qw<transform_hash>; our @EXPORT_OK = qw<transform_list some_func ...>; #... sub transform_list { ... } #... sub some_func { my %params = transform_hash @_; #... } #... 1 Suppose that enough of these utility functions are handy enough that I'll want to use them in BEGIN statements and import functions to process parameter lists or configuration data. I have been putting sub definitions into BEGIN blocks to make sure they are ready to use whenever somebody includes the module. But I have gotten into hairy race conditions where a definition is not completed in a BEGIN block. I put evolving code idioms into modules so that I can reuse any idiom I find myself coding over and over again. For instance: sub list_if { my $condition = shift; return unless $condition; my $more_args = scalar @_; my $arg_list = @_ > 1 ? \@_ : @_ ? shift : $condition; if (( reftype( $arg_list ) || '' ) eq 'ARRAY' ) { return wantarray ? @$arg_list : $arg_list; } elsif ( $more_args ) { return $arg_list; } return; } captures two idioms that I'm kind of tired of typing: @{ func_I_hope_returns_a_listref() || [] } and ( $condition ? LIST : ()) The more I define functions in BEGIN blocks, the more likely I'll use these idiom bricks to express the logic the more likely that bricks are needed in BEGIN blocks. Do people have standard ways of dealing with this sort of language-idiom-brick model? I've been doing mostly Pure-Perl; will XS alleviate some of this?

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  • The best way to structure this database?

    - by James P
    At the moment I'm doing this: gems(id, name, colour, level, effects, source) id is the primary key and is not auto-increment. A typical row of data would look like this: id => 40153 name => Veiled Ametrine colour => Orange level => 80 effects => +12 sp, +10 hit source => Ametrine (Some of you gamers might see what I'm doing here :) ) But I realise this could be sorted a lot better. I have studied database relationships and secondary keys in my A-Level computing class but never got as far as to set one up properly. I just need help with how this database should be organised, like what tables should have what data with what secondary and foreign keys? I was thinking maybe 3 tables: gem, effects, source. Which then have relationships to each other? Can anyone shed some light on this? Is a complex way like I'm proposing really the way to go or should I just carry on with what I'm doing? Cheers.

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