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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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  • Do null SQLite Data fields take up extra memory?

    - by CSharperWithJava
    I'm using the built in sqlite library on the Android platform. I'm considering adding several general purpose fields that users will be able to use for their own custom applications, but these fields will be blank most of the time. My question is, how much overhead will these blank fields add to my database? Do null fields even take up per record memory in sqlite? If so, how much? I don't quite understand the inner workings of a sqlite database.

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  • how to store data with many categories and many properties efficiently?

    - by Mickey Shine
    We have a large number of data in many categories with many properties, e.g. category 1: Book properties: BookID, BookName, BookType, BookAuthor, BookPrice category 2: Fruit properties: FruitID, FruitName, FruitShape, FruitColor, FruitPrice We have many categories like book and fruit. Obviously we can create many tables for them (MySQL e.g.), and each category a table. But this will have to create too many tables and we have to write many "adapters" to unify manipulating data. The difficulties are: 1) Every category has different properties and this results in a different data structure. 2) The properties of every categoriy may have to be changed at anytime. 3) Hard to manipulate data if each category a table (too many tables) How do you store such kind of data?

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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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  • Several C# Language Questions

    - by Water Cooler v2
    1) What is int? Is it any different from the struct System.Int32? I understand that the former is a C# alias (typedef or #define equivalant) for the CLR type System.Int32. Is this understanding correct? 2) When we say: IComparable x = 10; Is that like saying: IComparable x = new System.Int32(); But we can't new a struct, right? or in C like syntax: struct System.In32 *x; x=>someThing = 10; 3) What is String with a capitalized S? I see in Reflector that it is the sealed String class, which, of course, is a reference type, unlike the System.Int32 above, which is a value type. What is string, with an uncapitalized s, though? Is that also the C# alias for this class? Why can I not see the alias definitions in Reflector? 4) Try to follow me down this subtle train of thought, if you please. We know that a storage location of a particular type can only access properties and members on its interface. That means: Person p = new Customer(); p.Name = "Water Cooler v2"; // legal because as Name is defined on Person. but // illegal without an explicit cast even though the backing // store is a Customer, the storage location is of type // Person, which doesn't support the member/method being // accessed/called. p.GetTotalValueOfOrdersMade(); Now, with that inference, consider this scenario: int i = 10; // obvious System.object defines no member to // store an integer value or any other value in. // So, my question really is, when the integer is // boxed, what is the *type* it is actually boxed to. // In other words, what is the type that forms the // backing store on the heap, for this operation? object x = i; Update Thank you for your answers, Eric Gunnerson and Aaronought. I'm afraid I haven't been able to articulate my questions well enough to attract very satisfying answers. The trouble is, I do know the answers to my questions on the surface, and I am, by no means, a newbie programmer. But I have to admit, a deeper understanding to the intricacies of how a language and its underlying platform/runtime handle storage of types has eluded me for as long as I've been a programmer, even though I write correct code.

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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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  • 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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  • 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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  • 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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  • What considerations should be made when creating a reporting framework for a business?

    - by Andrew Dunaway
    It's a pretty classic problem. The company I work for has numerous business reports that are used to track sales, data feeds, and various other metrics. Of course this also means that there is a conglomerate of disparate frameworks, ASP.net pages, and areas where these reports can be found. There have been some attempts at consolidating these into a single entity, but nothing has stuck yet. Since this is a common problem, and I am sure solved innumerable times, I wanted to see what others have done. For the most part these can be boiled down to the following pieces: A SQL query against our database to gather data A presentation of data, generally in a data grid Filtering that can vary based on data types and the business needs Some way to organize the reports, a single drop down gets long and unmanageable quickly A method to download data to alter further, perhaps a csv file My first thought was to create a framework in Silverlight with Linq to Sql. Mainly just because I like it and want to play with it which probably is not the best reason. I also thought the controls grant a lot of functionality like sorting, dragging columns, etc. I was also curious about the printing in Silverlight 4. Which brings me around to my original question, what is the best way to do this? Is there a package out there I can just buy that will do it for me? The Silverlight approach seems pretty easy, after it's setup and templated, but maybe it's a bad idea and I can learn from someone else?

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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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  • What are provenly scalable data persistence solutions for consumer profiles?

    - by Hubbard
    Consumer profiles with analytical scores [ConsumerID, 1..n demographical variables, 1...n analytical scores e.g. "likely to churn" "likely to buy an item 100$ in worth" etc.] have to be possible to query fast if they are to be used in customizing web-sites, consumer communications etc. Well. If you have: Large number of consumers Large profiles with a huge set of variables (as profiles describing human behaviour are likely to be..) ...you are in trouble. If you really have a physical relational database to which you target a query and then a physical disk starts to rotate someplace to give you an individual profile or a set of profiles, the profile user (a web site customizing a page, a recommendation engine making a recommendation..) has died of boredom before getting any observable results. There is the possibility of having the profiles in memory, which would of course increase the performance hugely. What are the most proven solutions for a fast-response, scalable consumer profile storage? Is there a shootout of these someplace?

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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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  • 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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  • 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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  • Sql Server Development Server and Live

    - by Chris
    I have a database project that goes through iterations (only one so far) and I need to deploy a testing version to a live server. I'm not sure how to go about this. I can make all the changes in a copy and then remake those changes in the live version. That doesn't make sense. Is there a way to change a server name to an existing server? What's the best practice for this scenario?

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  • Session vs singleton pattern

    - by chobo
    Hi, I have a web application where I would like to pull user settings from a database and store them for Global access. Would it make more sense to store the data in a Singleton, or a Session object? What's the difference between the two? Is it better to store the data as an object reference or break it up into value type objects (ints and strings)? 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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  • 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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