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• What is the best database structure for this scenario?

  - by Ricketts

  I have a database that is holding real estate MLS (Multiple Listing Service) data. Currently, I have a single table that holds all the listing attributes (price, address, sqft, etc.). There are several different property types (residential, commercial, rental, income, land, etc.) and each property type share a majority of the attributes, but there are a few that are unique to that property type. My question is the shared attributes are in excess of 250 fields and this seems like too many fields to have in a single table. My thought is I could break them out into an EAV (Entity-Attribute-Value) format, but I've read many bad things about that and it would make running queries a real pain as any of the 250 fields could be searched on. If I were to go that route, I'd literally have to pull all the data out of the EAV table, grouped by listing id, merge it on the application side, then run my query against the in memory object collection. This also does not seem very efficient. I am looking for some ideas or recommendations on which way to proceed. Perhaps the 250+ field table is the only way to proceed. Just as a note, I'm using SQL Server 2012, .NET 4.5 w/ Entity Framework 5, C# and data is passed to asp.net web application via WCF service. Thanks in advance.

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• how do simple SQLAlchemy relationships work?

  - by Carson Myers

  I'm no database expert -- I just know the basics, really. I've picked up SQLAlchemy for a small project, and I'm using the declarative base configuration rather than the "normal" way. This way seems a lot simpler. However, while setting up my database schema, I realized I don't understand some database relationship concepts. If I had a many-to-one relationship before, for example, articles by authors (where each article could be written by only a single author), I would put an author_id field in my articles column. But SQLAlchemy has this ForeignKey object, and a relationship function with a backref kwarg, and I have no idea what any of it MEANS. I'm scared to find out what a many-to-many relationship with an intermediate table looks like (when I need additional data about each relationship). Can someone demystify this for me? Right now I'm setting up to allow openID auth for my application. So I've got this: from __init__ import Base from sqlalchemy.schema import Column from sqlalchemy.types import Integer, String class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) class OpenID(Base): __tablename__ = 'openid' url = Column(String, primary_key=True) user_id = #? I think the ? should be replaced by Column(Integer, ForeignKey('users.id')), but I'm not sure -- and do I need to put openids = relationship("OpenID", backref="users") in the Users class? Why? What does it do? What is a backref?

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• How do I write this MySQL query?

  - by CT

  I am working on an Asset DB using a lamp stack. In this example consider the following 5 tables: asset, server, laptop, desktop, software All tables have a primary key of id, which is a unique asset id. Every object has all asset attributes and then depending on type of asset has additional attributes in the corresponding table. If the type is a server, desktop or laptop it also has items in the software table. Here are the table create statements: // connect to mysql server and database "asset_db" mysql_connect("localhost", "asset_db", "asset_db") or die(mysql_error()); mysql_select_db("asset_db") or die(mysql_error()); // create asset table mysql_query("CREATE TABLE asset( id VARCHAR(50) PRIMARY KEY, company VARCHAR(50), location VARCHAR(50), purchase_date VARCHAR(50), purchase_order VARCHAR(50), value VARCHAR(50), type VARCHAR(50), notes VARCHAR(200))") or die(mysql_error()); echo "Asset Table Created.</br />"; // create software table mysql_query("CREATE TABLE software( id VARCHAR(50) PRIMARY KEY, software VARCHAR(50), license VARCHAR(50))") or die(mysql_error()); echo "Software Table Created.</br />"; // create laptop table mysql_query("CREATE TABLE laptop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Laptop Table Created.</br />"; // create desktop table mysql_query("CREATE TABLE desktop( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), serial_number VARCHAR(50), esc VARCHAR(50), user VARCHAR(50), prev_user VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Desktop Table Created.</br />"; // create server table mysql_query("CREATE TABLE server( id VARCHAR(50) PRIMARY KEY, manufacturer VARCHAR(50), model VARCHAR(50), warranty VARCHAR(50))") or die(mysql_error()); echo "Server Table Created.</br />"; ?> How do I query the database so that if I search by id, I receive all related fields to that asset id? Thank you.

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• Primary key/foreign Key naming convention

  - by Jeremy

  In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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• What should I do if i have a factory method which requires different parameters for different implem

  - by Sam Holder

  I have an interface, IMessage and a class which have several methods for creating different types of message like so: class MessageService { IMessage TypeAMessage(param 1, param 2) IMessage TypeBMessage(param 1, param 2, param 3, param 4) IMessage TypeCMessage(param 1, param 2, param 3) IMessage TypeDMessage(param 1) } I don't want this class to do all the work for creating these messages so it simply delegates to a MessageCreatorFactory which produces an IMessageCreator depending on the type given (an enumeration based on the type of the message TypeA, TypeB, TypeC etc) interface IMessageCreator { IMessage Create(MessageParams params); } So I have 4 implementations of IMessageCreator: TypeAMessageCreator, TypeBMessageCreator, TypeCMessageCreator, TypeDMessageCreator I ok with this except for the fact that because each type requires different parameters I have had to create a MessageParams object which contains 4 properties for the 4 different params, but only some of them are used in each IMessageCreator. Is there an alternative to this? One other thought I had was to have a param array as the parameter in the Create emthod, but this seems even worse as you don't have any idea what the params are. Or to create several overloads of Create in the interface and have some of them throw an exception if they are not suitable for that particular implementation (ie you called a method which needs more params, so you should have called one of the other overloads.) Does this seem ok? Is there a better solution?

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• Sorting out POCO, Repository Pattern, Unit of Work, and ORM

  - by CoffeeAddict

  I'm reading a crapload on all these subjects: POCO Repository Pattern Unit of work Using an ORM mapper ok I see the basic definitions of each in books, etc. but I can't visualize this all together. Meaning an example structure (DL, BL, PL). So what, you have your DL objects that contain your CRUD methods, then your BL objects which are "mapped" using an ORM back to your DL objects? What about DTOs...they're your DL objects right? I'm confused. Can anyone really explain all this together or send me example code? I'm just trying to put this together. I am determining whether to go LINQ to SQL or EF 4 (not sure about NHibrernate yet). Just not getting the concepts as in physical layers and code layers here and what each type of object contains (just properties for DTOs, and CRUDs for your core DL classes that match the table fields???). I just need some guidance here. I'm reading Fowler's books and starting to read Evans but just not all there yet.

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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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• Measuring time spent in application / thread

  - by Adamski

  I am writing a simulation in Java whereby objects act under Newtonian physics. An object may have a force applied to it and the resulting velocity causes it to move across the screen. The nature of the simulation means that objects move in discrete steps depending on the time ellapsed between the current and previous iteration of the animation loop; e.g public void animationLoop() { long prev = System.currentTimeMillis(); long now; while(true) { long now = System.currentTimeMillis(); long deltaMillis = now - prev; prev = now; if (deltaMillis > 0) { // Some time has passed for (Mass m : masses) { m.updatePosition(deltaMillis); } // Do all repaints. } } } A problem arises if the animation thread is delayed in some way causing a large amount of time to ellapse (the classic case being under Windows whereby clicking and holding on minimise / maximise prevents a repaint), which causes objects to move at an alarming rate. My question: Is there a way to determine the time spent in the animation thread rather than the wallclock time, or can anyone suggest a workaround to avoid this problem? My only thought so far is to contstrain deltaMillis by some upper bound.

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• Does C# allow method overloading, PHP style (__call)?

  - by mr.b

  In PHP, there is a special method named __call($calledMethodName, $arguments), which allows class to catch calls to non-existing methods, and do something about it. Since most of classic languages are strongly typed, compiler won't allow calling a method that does not exist, I'm clear with that part. What I want to accomplish (and I figured this is how I would do it in PHP, but C# is something else) is to proxy calls to a class methods and log each of these calls. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); pc.inner.B(); // ... So, how can I proxy calls to an object instance in extensible way? Extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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• Delivering activity feed items in a moderately scalable way

  - by sotangochips

  The application I'm working on has an activity feed where each user can see their friends' activity (much like Facebook). I'm looking for a moderately scalable way to show a given users' activity stream on the fly. I say 'moderately' because I'm looking to do this with just a database (Postgresql) and maybe memcached. For instance, I want this solution to scale to 200k users each with 100 friends. Currently, there is a master activity table that stores the rendered html for the given activity (Jim added a friend, George installed an application, etc.). This master activity table keeps the source user, the html, and a timestamp. Then, there's a separate ('join') table that simply keeps a pointer to the person who should see this activity in their friend feed, and a pointer to the object in the main activity table. So, if I have 100 friends, and I do 3 activities, then the join table will then grow to 300 items. Clearly this table will grow very quickly. It has the nice property, though, that fetching activity to show to a user takes a single (relatively) inexpensive query. The other option is to just keep the main activity table and query it by saying something like: select * from activity where source_user in (1, 2, 44, 2423, ... my friend list) This has the disadvantage that you're querying for users who may never be active, and as your friend list grows, this query can get slower and slower. I see the pros and the cons of both sides, but I'm wondering if some SO folks might help me weigh the options and suggest one way or they other. I'm also open to other solutions, though I'd like to keep it simple and not install something like CouchDB, etc. Many thanks!

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• What makes an effective UI for displaying versioning of structured hierarchical data

  - by Fadrian Sudaman

  Traditional version control system are displaying versioning information by grouping Projects-Folders-Files with Tree view on the left and details view on the right, then you will click on each item to look at revision history for that configuration history. Assuming that I have all the historical versioning information available for a project from Object-oriented model perspective (e.g. classes - methods - parameters and etc), what do you think will be the most effective way to present such information in UI so that you can easily navigate and access the snapshot view of the project and also the historical versioning information? Put yourself in the position that you are using a tool like this everyday in your job like you are currently using SVN, SS, Perforce or any VCS system, what will contribute to the usability, productivity and effectiveness of the tool. I personally find the classical way for display folders and files like above are very restrictive and less effective for displaying deep nested logical models. Assuming that this is a greenfield project and not restricted by specific technology, how do you think I should best approach this? I am looking for idea and input here to add values to my research project. Feel free to make any suggestions that you think is valuable. Thanks again for anyone that shares their thoughts.

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• What should go in each MVVM triad?

  - by Harry

  OK, let's say I am creating a program that will list users contacts in a ListBox on the left side of the screen. When a user clicks on the contact, a bunch of messages or whatever appears in the main part of the window. Now my question is: how should the MVVM triads look? I have two models: Contact, and Message. The Contact model contains a list of Message models. Each ViewModel object will contain a single corresponding Model, right? And what about the Views? I have a "MainView" that is the main window, that will have things like the menu, toolbar etc. Do I put the ListBox in the MainView? My confusion is with what to put where; for example, what should the ContactView contain? Just a single instance of a contact? So the DataTemplate, ControlTemplate, context menus, styles etc for that single contact, and then just have a ListBox of them in the MainView...? Thanks.

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• In M-V-VM where does my code go?

  - by Nate Bross

  So, this is a pretty basic question I hope. I have a web service that I've added through Add Service Reference. It has some methods to get list and get detail of a perticular table in my database. What I'm trying to do is setup a UI as follows: App Load Load service proxy Call the GetList(); method display the results in a ListBox control User Double Clicks item in ListBox, display a modal dialog with a "detail" view I'm extremely new to using MVVM, so any help would be greatly appreciated. Additional information: // Service Interface (simplification): interface IService { IEnumerable<MyObject> GetList(); MyObject GetDetail(int id); } // Data object (simplification) class MyObject { public int ID { get; set; } public string Name { get; set; } } I'm thinking I should have something like this: MainWindow MyObjectViewUserControl Displays list Opens modal window on double click Specific Questions: What would my ViewModel class look like? Where does the code to handle the double click go? Inside the UserControl? Sorry for the long details, but I'm very new to the whole thing and I'm not educated enough to ask the right questions. I checked out the MVVM Sample from wpf.codeplex.com and something isn't quite clicking for me yet, because it seems very confusing.

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• Open closed prinicple, problem

  - by Marcus

  Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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• C++. How to define template parameter of type T for class A when class T needs a type A template parameter?

  - by jaybny

  Executor class has template of type P and it takes a P object in constructor. Algo class has a template E and also has a static variable of type E. Processor class has template T and a collection of Ts. Question how can I define Executor< Processor<Algo> > and Algo<Executor> ? Is this possible? I see no way to defining this, its kind of an "infinite recursive template argument" See code. template <class T> class Processor { map<string,T> ts; void Process(string str, int i) { ts[str].Do(i); } } template <class P> class Executor { Proc &p; Executor(P &p) : Proc(p) {} void Foo(string str, int i) { p.Process(str,i); } Execute(string str) { } } template <class E> class Algo { static E e; void Do(int i) {} void Foo() { e.Execute("xxx"); } } main () { typedef Processor<Algo> PALGO; // invalid typedef Executor<PALGO> EPALGO; typedef Algo<EPALGO> AEPALGO; Executor<PALGO> executor(PALGO()); AEPALGO::E = executor; }

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• Protecting sensitive entity data

  - by Andreas

  Hi, I'm looking for some advice on architecture for a client/server solution with some peculiarities. The client is a fairly thick one, leaving the server mostly to peristence, concurrency and infrastructure concerns. The server contains a number of entities which contain both sensitive and public information. Think for example that the entities are persons, assume that social security number and name are sensitive and age is publicly viewable. When starting the client, the user is presented with a number of entities, not disclosing any sensitive information. At any time the user can choose to log in and authenticate against the server, given the authentication is successful the user is granted access to the sensitive information. The client is hosting a domain model and I was thinking of implementing this as some kind of "lazy loading", making the first request instantiating the entities and later refreshing them with sensitive data. The entity getters would throw exceptions on sensitive information when they've not been disclosed, f.e.: class PersonImpl : PersonEntity { private bool undisclosed; public override string SocialSecurityNumber { get { if (undisclosed) throw new UndisclosedDataException(); return base.SocialSecurityNumber; } } } Another more friendly approach could be to have a value object indicating that the value is undisclosed. get { if (undisclosed) return undisclosedValue; return base.SocialSecurityNumber; } Some concerns: What if the user logs in and then out, the sensitive data has been loaded but must be disclosed once again. One could argue that this type of functionality belongs within the domain and not some infrastructural implementation(i.e. repository implementations). As always when dealing with a larger number of properties there's a risk that this type of functionality clutters the code Any insights or discussion is appreciated!

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• Auto scale and rotate images

  - by Dave Jarvis

  Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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• How do you unit test new code that uses a bunch of classes that cannot be instantiated in a test har

  - by trendl

  I'm writing a messaging layer that should handle communication with a third party API. The API has a bunch of classes that cannot be easily (if at all) instantiated in a test harness. I decided to wrap each class that I need in my unit tests with an adapter/wrapper and expose the members I need through this adapter class. Often I need to expose the wrapped type as well which I do by exposing it as an object. I have also provided an interface for for each or the adapter classes to be able to use them with a mocking framework. This way I can substitute the classes in test for whatever I need. The downside is that I have a bunch of adapter classes that so far server no other reason but testing. For me this is a good reason by itself but others may find this not enough. Possibly, when I write an implementation for another third party vendor's API, I may be able to reuse much of my code and only provide the adapters specific to the vendor's API. However, this is a bit of a long shot and I'm not actually sure it will work. What do you think? Is this approach viable or am I writing unnecessary code that serves no real purpose? Let me say that I do want to write unit tests for my messaging layer and I do now know how to do it otherwise.

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• How can I handle all my errors/messages in one place on an Asp.Net page?

  - by Atomiton

  Hi all, I'm looking for some guidance here. On my site I put things in Web user controls. For example, I will have a NewsItem Control, an Article Control, a ContactForm control. These will appear in various places on my site. What I'm looking for is a way for these controls to pass messages up to the Page that they exist on. I don't want to tightly couple them, so I think I will have to do this with Events/Delegates. I'm a little unclear as to how I would implement this, though. A couple of examples: 1 A contact form is submitted. After it's submitted, instead of replacing itself with a "Your mail has been sent" which limits the placement of that message, I'd like to just notify the page that the control is on with a Status message and perhaps a suggested behaviour. So, a message would include the text to render as well as an enum like DisplayAs.Popup or DisplayAs.Success 2 An Article Control queries the database for an Article object. Database returns an Exception. Custom Exception is passed to the page along with the DisplayAs.Error enum. The page handles this error and displays it wherever the errors go. I'm trying to accomplish something similar to the ValidationSummary Control, except that I want the page to be able to display the messages as the enum feels fit. Again, I don't want to tightly bind or rely a control existing on the Page. I want the controls to raise these events, but the page can ignore them if it wants. Am I going about this the right way? I'd love a code sample just to get me started. I know this is a more involved question, so I'll wait longer before voting/choosing the answers.

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• Domain model for an online WYSYWG webpage generator / runtime

  - by CharlieBrown

  Hi all, I'm using C#, MVC, NHibernate and StructureMap as my IoC container, and need some ideas regarding my domain model. The application I'm working has two parts: an Authoring part and a Runtime part. The idea is to allow the user to create a webpage in Authoring (mostly a form actually) by choosing from a set of predefined controls. That webpage will be later used as a form in a call center environment (Runtime part), or may be used in an intranet portal, etc. Basically something similar to what a CMS would do. The difference is, of course, that the webpage/form the author generates will be used and fulfilled in runtime, and that authros should be able to freely create the webpage they want without limitations. I have a draft working model that allows a RunController to iterate over the ScriptPage (my class for the "generated webpage") Controls collection and uses partial views to render each of them. Works kind of fine. Basically I have a common ScriptControl class, and then I can create for example a TextInputControl or a DropDownControl by inheriting from that base class. I can also figure out the Authoring part of the app, although that will surely be fun in itself for sure. :) The biggest problem I have now is persistance. In order to be flexible, I want to be able to add more controls, and template controls (think of an Address composite control) in sepparate DLLs, so I think having a relational model that handles very possible control is not the way to go. My current thinking is using a kind of ObjectStore: binary-serializing the ScriptPage object that contains the List collection and deserializing at Runtime, but I'm not sure how good will it work with NHibernate and how good the performance will be. Serializing a small "page" with 10 controls results in 7964 bytes, for example. Any ideas out there? Thanks in advance, excuse the length. ;)

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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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• HTML columns or rows for form layout?

  - by Valera

  I'm building a bunch of forms that have labels and corresponding fields (input element or more complex elements). Labels go on the left, fields go on the right. Labels in a given form should all be a specific width so that the fields all line up vertically. There are two ways (maybe more?) of achieving this: Rows: Float each label and each field left. Put each label and field in a field-row div/container. Set label width to some specific number. With this approach labels on different forms will have different widths, because they'll depend on the width of the text in the longest label. Columns: Put all labels in one div/container that's floated left, put all fields in another floated left container with padding-left set. This way the labels and even the label container don't need to have their widths set, because the column layout and the padding-left will uniformly take care of vertically lining up all the fields. So approach #2 seems to be easier to implement (because the widths don't need to be set all the time), but I think it's also less object oriented, because a label and a field that goes with that label are not grouped together, as they are in approach #1. Also, if building forms dynamically, approach #2 doesn't work as well with functions like addRow(label, field), since it would have to know about the label and the field containers, instead of just creating/adding one field-row element. Which approach do you think is better? Is there another, better approach than these two?

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• Global State and Singletons Dependency injection

  - by Manu

  this is a problem i face lot of times when i am designing a new app i'll use a sample problem to explain this think i am writing simple game.so i want to hold a list of players. i have few options.. 1.use a static field in some class private static ArrayList<Player> players = new ArrayList<Integer>(); public Player getPlayer(int i){ return players.get(i); } but this a global state 2.or i can use a singleton class PlayerList{ private PlayerList instance; private PlayerList(){...} public PlayerList getInstance() { if(instance==null){ ... } return instance; } } but this is bad because it's a singleton 3.Dependency injection class Game { private PlayerList playerList; public Game(PlayerList list) { this.list = list; } public PlayerList getPlayerList() { return playerList; } } this seems good but it's not, if any object outside Game need to look at PlayerList (which is the usual case) i have to use one of the above methods to make the Game class available globally. so I just add another layer to the problem. didn't actually solve anything. what is the optimum solution ? (currently i use Singleton approach)

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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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• Static selection and Ruby on Rails objects

  - by Dave

  Hi all- I have a simple problem, but am having trouble wrapping my head around it. I have an video object that should have one or more "genres". This list of genres should be prepopulated and then the user should just select one or more using autocomplete or some such. Here is the question: Is it worth creating a table with genres for the static selection? Or should it just be included in the presentation layer? If there is a static table, how do we name it correctly. I envision something like this class Video < ActiveRecord::Base has_many :genres ... end class Genre < ... belongs_to :video ... end But then we get a table called genre, that basically maps all the selected genres to their parent videos. There would need to be some static table to reference the static genres. Is this the best way to do it? Sorry if this was rambl-y a little stream of conciousness. Thanks!

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