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  • Proper Usage of SqlConnection in .NET

    - by Jojo
    Hi guys, I just want an opinion on the proper usage or a proper design with regards to using SqlConnection object. Which of the 2 below is the best use: A data provider class whose methods (each of them) contain SqlConnection object (and disposed when done). Like: IList<Employee> GetAllEmployees() { using (SqlConnection connection = new SqlConnection(this.connectionString)) { // Code goes here... } } Employee GetEmployee(int id) { using (SqlConnection connection = new SqlConnection(this.connectionString)) { // Code goes here... } } or SqlConnection connection; // initialized in constructor IList<Employee> GetAllEmployees() { this.TryOpenConnection(); // tries to open member SqlConnection instance // Code goes here... this.CloseConnection(); // return } Employee GetEmployee(int id) { this.TryOpenConnection(); // tries to open member SqlConnection instance // Code goes here... this.CloseConnection(); // return } Or is there a better approach than this? I have a focused web crawler type of application and this application will crawl 50 or more websites simultaneously (multithreaded) with each website contained in a crawler object and each crawler object has an instance of a data provider class (above). Please advise. Thanks.

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  • How can we best represent the SDLC process as a board game?

    - by Innogetics
    I recently got interested in financial board games and saw how they can be very useful in educating children about certain concepts. It got me thinking whether it was also possible to represent certain aspects of executing a software project via a boardgame and make it fun. Here are a few things that I have come up so far: human resources and tools / techniques are represented as cards. requirements are also represented as cards, which are dealt equally to each player, and the objective is to move all requirement cards through an "SDLC" board (one per player) that represent a series of squares grouped according to phases (design all the way to deployment) the passage of time is represented in a main square board like monopoly, and completing a trip around the board (passing "Go") allows the player to move each of the requirement cards a number of steps through the SDLC board depending on the capability of the resource cards (senior programmer allows one requirement to move two squares in the dev phase, junior programmer only one, etc.) players will start with play money representing the project budget, and at every pass at "Go" is payday. the player is out of the game if he runs out of funds. the main board also has "chance" / "risk" cards, which represent things that can mess up a project. damage is applied at the roll of a die, and chance modifiers depend on whether the user has "bought" tools / techniques. I haven't implemented this idea yet as I'm still looking at more play elements that can make the game more engaging, as well as soliciting for more ideas. I am planning to release this under Creative Commons license but haven't decided on the exact license yet. Any more game play suggestions are welcome. UPDATE: This was posted in BoardGameGeek and there's now an active discussion thread there. http://www.boardgamegeek.com/article/4436694

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  • Is it wise to use temporary tables?

    - by Industrial
    Hi guys, We have a mySQL database table for products. We are utilizing a cache layer to reduce database load, but we think that it's a good idea to minimize the actual data needed to be stored in the cache layer to speed up the application further. All the products in the database, that is visible to visitors have a price attached to them: The prices are stored in a different table, called prices . There are multiple price categories depending on which discount level each visitor (customer) applies to. From time to time, there are campaigns which means that a special price for each product is available. The special prices are stored in a table called specials. Is it a bad to make a temp table that binds the tables together? It would only have the neccessary information and would ofcourse be cached. -------------|-------------|------------ | productId | hasPrice | hasSpecial -------------|-------------|------------ 1 | 1 | 0 2 | 1 | 1 By doing such, it would be super easy to know if the specific product really has a price, without having to iterate through the complete prices or specials table each time a product should be listed or presented. Are temp tables a common thing for web applications or is it just bad design?

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  • Using collections/containers/catalogs in Domain Models

    - by devoured elysium
    Let's say I want to model a cinema. The cinema will have a couple of rooms(for example, 7), where the movies are being played. I wonder how should I design the domain model for this scenario. Should the Cinema class concept concept have a direct association with the 7 rooms? Should the Cinema class concept have an association with a catalog of the 7 rooms? Why? I am having some trouble understanding why in some places I see the first case and in some others I see something like the second case. If instead of rooms, I wanted to depict the relationship between Cinema and: Tickets to sell (today). Tickets already sold (today) Customers in the Cinema database The set of hours at which there are movies playing in a given room in the cinema. The set of places you can sit at in a room in the cinema. Should I use catalogs, should I connect them directly to the Cinema concept with a multiplicity of * in the target? Thanks

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  • Hierarchical/Nested Database Structure for Comments

    - by Stephen Melrose
    Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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  • C# using the "this" keyword in this situation?

    - by Alex
    Hi, I've completed a OOP course assignment where I design and code a Complex Number class. For extra credit, I can do the following: Add two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When adding two complex numbers, the real part of the calling object is added to the real part of the complex number object passed as a parameter, and the imaginary part of the calling object is added to the imaginary part of the complex number object passed as a parameter. Subtract two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When subtracting two complex numbers, the real part of the complex number object passed as a parameter is subtracted from the real part of the calling object, and the imaginary part of the complex number object passed as a parameter is subtracted from the imaginary part of the calling object. I have coded this up, and I used the this keyword to denote the current instance of the class, the code for my add method is below, and my subtract method looks similar: public ComplexNumber Add(ComplexNumber c) { double realPartAdder = c.GetRealPart(); double complexPartAdder = c.GetComplexPart(); double realPartCaller = this.GetRealPart(); double complexPartCaller = this.GetComplexPart(); double finalRealPart = realPartCaller + realPartAdder; double finalComplexPart = complexPartCaller + complexPartAdder; ComplexNumber summedComplex = new ComplexNumber(finalRealPart, finalComplexPart); return summedComplex; } My question is: Did I do this correctly and with good style? (using the this keyword)?

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  • Generic FSM for game in C++ ?

    - by Mr.Gando
    Hello, I was wondering if there's a way I could code some kind of "generic" FSM for a game with C++?. My game has a component oriented design, so I use a FSM Component. my Finite State Machine (FSM) Component, looks more or less this way. class gecFSM : public gecBehaviour { public: //Constructors gecFSM() { state = kEntityState_walk; } gecFSM(kEntityState s) { state = s; } //Interface void setRule(kEntityState initialState, int inputAction, kEntityState resultingState); void performAction(int action); private: kEntityState fsmTable[MAX_STATES][MAX_ACTIONS]; }; I would love to hear your opinions/ideas or suggestions about how to make this FSM component, generic. With generic I mean: 1) Creating the fsmTable from an xml file is really easy, I mean it's just a bunch of integers that can be loaded to create an MAX_STATESxMAX_ACTION matrix. void gecFSM::setRule(kEntityState initialState, int inputAction, kEntityState resultingState) { fsmTable[initialState][inputAction] = resultingState; } 2) But what about the "perform Action" method ? void gecFSM::performAction(int action) { switch( smTable[ ownerEntity->getState() ][ action ] ) { case WALK: /*Walk action*/ break; case STAND: /*Stand action*/ break; case JUMP: /*Jump action*/ break; case RUN: /*Run action*/ break; } } What if I wanted to make the "actions" and the switch generic? This in order to avoid creating a different FSM component class for each GameEntity? (gecFSMZombie, gecFSMDryad, gecFSMBoss etc ?). That would allow me to go "Data Driven" and construct my generic FSM's from files for example. What do you people suggest?

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  • Do you use Styrofoam balls to model your systems?

    - by Nick D
    [Objective-C] Do you still use Styrofoam balls to model your systems, where each ball represents a class? Tom Love: We do, actually. We've also done a 3D animation version of it, which we found to be nowhere near as useful as the Styrofoam balls. There's something about a physical, conspicuous structure hanging from the ceiling right in the middle of a development project that's regularly updated to provide not only the structure of the system that you're building, but also the current status of each one of the classes. We've done it on 19 projects the last time I've counted. One of them was 1,856 classes, which is big - actually, probably bigger than it should be. It was a big commercial project, so it needed to be somewhat big. Masterminds of Programming It is the first time I've read or heard about using styrofoam balls to model classes. Is that a commonly used technique? And, how does that sort of modeling help us to design better the system? If you have any photos to share which can show us how the classes are represented it'd be great!

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  • HTML Submit button vs AJAX based Post (ASP.NET MVC)

    - by Graham
    I'm after some design advice. I'm working on an application with a fellow developer. I'm from the Webforms world and he's done a lot with jQuery and AJAX stuff. We're collaborating on a new ASP.MVC 1.0 app. He's done some pretty amazing stuff that I'm just getting my head around, and used some 3rd party tools etc. for datagrids etc. but... He rarely uses Submit buttons whereas I use them most of the time. He uses a button but then attaches Javascript to it that calls an MVC action which returns a JSON object. He then parses the object to update the datagrid. I'm not sure how he deals with server-side validation - I think he adds a message property to the JSON object. A sample scenario would be to "Save" a new record that then gets added to the gridview. The user doesn't see a postback as such, so he uses jQuery to disable the UI whilst the controller action is running. TBH, it looks pretty cool. However, the way I'd do it would be to use a Submit button to postback, let the ModelBinder populate a typed model class, parse that in my controller Action method, update the model (and apply any validation against the model), update it with the new record, then send it back to be rendered by the View. Unlike him, I don't return a JSON object, I let the View (and datagrid) bind to the new model data. Both solutions "work" but we're obviously taking the application down different paths so one of us has to re-work our code... and we don't mind whose has to be done. What I'd prefer though is that we adopt the "industry-standard" way of doing this. I'm unsure as to whether my WebForms background is influencing the fact that his way just "doesn't feel right", in that a "submit" is meant to submit data to the server. Any advice at all please - many thanks.

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  • Conditional column values in NSTableView?

    - by velocityb0y
    I have an NSTableView that binds via an NSArrayController to an NSMutableArray. What's in the array are derived classes; the first few columns of the table are bound to properties that exist on the base class. That all works fine. Where I'm running into problem is a column that should only be populated if the row maps to one specific subclass. The property that column is meant to display only exists in that subclass, since it makes no sense in terms of the base class. The user will know, from the first two columns, why the third column's cell is populated/editable or not. The binding on the third column's value is on arrangedObjects, with a model path of something like "foo.name" where foo is the property on the subclass. However, this doesn't work, as the other subclasses in the hierarchy are not key-value compliant for foo. It seems like my only choice is to have foo be a property on the base class so everybody responds to it, but this clutters up the interfaces of the model objects. Has anyone come up with a clean design for this situation? It can't be uncommon (I'm a relative newcomer to Cocoa and I'm just learning the ins and outs of bindings.)

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  • dynamical binding or switch/case?

    - by kingkai
    A scene like this: I've different of objects do the similar operation as respective func() implements. There're 2 kinds of solution for func_manager() to call func() according to different objects Solution 1: Use virtual function character specified in c++. func_manager works differently accroding to different object point pass in. class Object{ virtual void func() = 0; } class Object_A : public Object{ void func() {}; } class Object_B : public Object{ void func() {}; } void func_manager(Object* a) { a->func(); } Solution 2: Use plain switch/case. func_manager works differently accroding to different type pass in typedef _type_t { TYPE_A, TYPE_B }type_t; void func_by_a() { // do as func() in Object_A } void func_by_b() { // do as func() in Object_A } void func_manager(type_t type) { switch(type){ case TYPE_A: func_by_a(); break; case TYPE_B: func_by_b(); default: break; } } My Question are 2: 1. at the view point of DESIGN PATTERN, which one is better? 2. at the view point of RUNTIME EFFCIENCE, which one is better? Especailly as the kinds of Object increases, may be up to 10-15 total, which one's overhead oversteps the other? I don't know how switch/case implements innerly, just a bunch of if/else? Thanks very much!

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  • Domain model for an optional many-many relationship

    - by Greg
    Let's say I'm modeling phone numbers. I have one entity for PhoneNumber, and one for Person. There's a link table that expresses the link (if any) between the PhoneNumber and Person. The link table also has a field for DisplayOrder. When accessing my domain model, I have several Use Cases for viewing a Person. I can look at them without any PhoneNumber information. I can look at them for a specific PhoneNumber. I can look at them and all of their current (or past) PhoneNumbers. I'm trying to model Person, not only for the standard CRUD operations, but for the (un)assignment of PhoneNumbers to a Person. I'm having trouble expressing the relationship between the two, especially with respects to the DisplayOrder property. I can think of several solutions but I'm not sure of which (if any) would be best. A PhoneNumberPerson class that has a Person and PhoneNumber property (most closely resembles database design) A PhoneCarryingPerson class that inherits from Person and has a PhoneNumber property. A PhoneNumber and/or PhoneNumbers property on Person (and vis-a-versa, a Person property on PhoneNumber) What would be a good way to model this that makes sense from a domain model perspective? How do I avoid misplaced properties (DisplayOrder on Person) or conditionally populated properties?

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  • Insert data in an object to a database.

    - by paul
    I am facing the following design/implementation dilemma. I have a class Customer which is below with getters and setters. I would like to insert the value of the Customer into a "Customer" table of a database. But Customer has an address which is of type "Address". How do I go about inserting this field into the database?(I am using sqlite3). I thought of writing a separate table "Address(customerId,doorNo,city,state,country,pinCode)". But I am having second thoughts about generating the primary key(customerId) which should be same for both the "customer" and "Address" table. Sqlite3 faq states that I can do "Integer Primary Key" to use the field to generate an auto number. But if I do that in customer table, I would have to retrieve the same Id to be used in Address table. This kinda looks wrong to me :-?. There should be an elegant method to solve this. Any ideas would be much appreciated. Thanks in advance. import java.io.*; import java.sql.*; class Customer { private String id; private String name; private Address address; private Connection connection; private ResultSet resultSet; private PreparedStatement preparedStatement; public void insertToDatabase(){ } } class Address{ private String doorNumber; private String streetName; private String cityName; private String districtName; private String stateName; private String countryName; private long pinCode; }

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  • Why is JavaMail Transport.send() a static method?

    - by skiphoppy
    I'm revising code I did not write that uses JavaMail, and having a little trouble understanding why the JavaMail API is designed the way it is. I have the feeling that if I understood, I could be doing a better job. We call: transport = session.getTransport("smtp"); transport.connect(hostName, port, user, password); So why is Eclipse warning me that this: transport.send(message, message.getAllRecipients()); is a call to a static method? Why am I getting a Transport object and providing settings that are specific to it if I can't use that object to send the message? How does the Transport class even know what server and other settings to use to send the message? It's working fine, which is hard to believe. What if I had instantiated Transport objects for two different servers; how would it know which one to use? In the course of writing this question, I've discovered that I should really be calling: transport.sendMessage(message, message.getAllRecipients()); So what is the purpose of the static Transport.send() method? Is this just poor design, or is there a reason it is this way?

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  • Bulletin board - Database optimisation

    - by andrew
    This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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  • Applying the Decorator Pattern to Forms

    - by devoured elysium
    I am trying to apply the Decorator Design Pattern to the following situation: I have 3 different kind of forms: Green, Yellow, Red. Now, each of those forms can have different set of attributes. They can have a minimize box disabled, a maximized box disabled and they can be always on top. I tried to model this the following way: Form <---------------------------------------FormDecorator /\ /\ |---------|-----------| |----------------------|-----------------| GreenForm YellowForm RedForm MinimizeButtonDisabled MaximizedButtonDisabled AlwaysOnTop Here is my GreenForm code: public class GreenForm : Form { public GreenForm() { this.BackColor = Color.GreenYellow; } public override sealed Color BackColor { get { return base.BackColor; } set { base.BackColor = value; } } } FormDecorator: public abstract class FormDecorator : Form { private Form _decoratorForm; protected FormDecorator(Form decoratorForm) { this._decoratorForm = decoratorForm; } } and finally NoMaximizeDecorator: public class NoMaximizeDecorator : FormDecorator { public NoMaximizeDecorator(Form decoratorForm) : base(decoratorForm) { this.MaximizeBox = false; } } So here is the running code: static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(CreateForm()); } static Form CreateForm() { Form form = new GreenForm(); form = new NoMaximizeDecorator(form); form = new NoMinimizeDecorator(form); return form; } The problem is that I get a form that isn't green and that still allows me to maximize it. It is only taking in consideration the NoMinimizeDecorator form. I do comprehend why this happens but I'm having trouble understanding how to make this work with this Pattern. I know probably there are better ways of achieving what I want. I made this example as an attempt to apply the Decorator Pattern to something. Maybe this wasn't the best pattern I could have used(if one, at all) to this kind of scenario. Is there any other pattern more suitable than the Decorator to accomplish this? Am I doing something wrong when trying to implement the Decorator Pattern? Thanks

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  • Endianness and C API's: Specifically OpenSSL.

    - by Hassan Syed
    I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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  • css layout for footer at bottom with dynamic ajax content changing height of page

    - by m42
    [Update] I actually compromised on this problem for now by foregoing the fixed footer design. It seems that there is no problem with dynamic content moving the footer and resizing containers appropriately unless the footer is fixed to the browser bottom initially. I hope others will eventually provide a great solution that encompasses the best of both worlds. I spent all day trying to get the footer to move down the page to accommodate dynamically added (via ajax) content. I really need some pointers or links because I haven't found anything that helps. Basically: My site has some pages that begin with only a text box and a button so that the total height of the content area is only a few inches beneath the header area. I don't have any problem getting the sticky footer working so that the footer appears at the bottom of the browser window even when there is very little content on screen. That same css layout works fine for other pages that have content that extends beneath the browser window. The catch: The content has to be rendered and passed to the browser with the initial load. The Problem: Any content that is added to the page via AJAX after the initial load paints down the page correctly -- but the footer remains in its initial location. Please tell me there is a fix for this. I can't post the css until checking with my boss first - if possible - and if needed, I will later - but it's just a very basic version of the many sticky footer css solutions floating around the web. Thanks.

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  • Refactoring code/consolidating functions (e.g. nested for-loop order)

    - by bmay2
    Just a little background: I'm making a program where a user inputs a skeleton text, two numbers (lower and upper limit), and a list of words. The outputs are a series of modifications on the skeleton text. Sample inputs: text = "Player # likes @." (replace # with inputted integers and @ with words in list) lower = 1 upper = 3 list = "apples, bananas, oranges" The user can choose to iterate over numbers first: Player 1 likes apples. Player 2 likes apples. Player 3 likes apples. Or words first: Player 1 likes apples. Player 1 likes bananas. Player 1 likes oranges. I chose to split these two methods of outputs by creating a different type of dictionary based on either number keys (integers inputted by the user) or word keys (from words in the inputted list) and then later iterating over the values in the dictionary. Here are the two types of dictionary creation: def numkey(dict): # {1: ['Player 1 likes apples', 'Player 1 likes...' ] } text, lower, upper, list = input_sort(dict) d = {} for num in range(lower,upper+1): l = [] for i in list: l.append(text.replace('#', str(num)).replace('@', i)) d[num] = l return d def wordkey(dict): # {'apples': ['Player 1 likes apples', 'Player 2 likes apples'..] } text, lower, upper, list = input_sort(dict) d = {} for i in list: l = [] for num in range(lower,upper+1): l.append(text.replace('#', str(num)).replace('@', i)) d[i] = l return d It's fine that I have two separate functions for creating different types of dictionaries but I see a lot of repetition between the two. Is there any way I could make one dictionary function and pass in different values to it that would change the order of the nested for loops to create the specific {key : value} pairs I'm looking for? I'm not sure how this would be done. Is there anything related to functional programming or other paradigms that might help with this? The question is a little abstract and more stylistic/design-oriented than anything.

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  • Where to store site settings: DB? XML? CONFIG? CLASS FILES?

    - by Emin
    I am re-building a news portal of which already have a large number of visits every day. One of the major concerns when re-building this site was to maximize performance and speed. Having said this, we have done many things from caching, to all sort of other measures to ensure speed. Now towards the end of the project, I am having a dilemma of where to store my site settings that would least affect performance. The site settings will include things such as: Domain, DefaultImgPath, Google Analytics code, default emails of editors as well as more dynamic design/display feature settings such as the background color of specific DIVs and default color for links etc.. As far as I know, I have 4 choices in storing all these info. Database: Storing general settings in the DB and caching them may be a solution however, I want to limit the access to the database for only necessary and essential functions of the project which generally are insert/update/delete news items, author articles etc.. XML: I can store these settings in an XML file but I have not done this sort of thing before so I don't know what kind of problems -if any- I might face in the future. CONFIG: I can also store these settings in web.config CLASS FILE: I can hard code all these settings in a SiteSettings class, but since the site admin himself will be able to edit these settings, It may not be the best solution. Currently, I am more close to choosing web.config but letting people fiddle with it too often is something I do not want. E.g. if somehow, I miss out a validation for something and it breaks the web.config, the whole site will go down. My concern basically is that, I cannot forsee any possible consequences of using any of the methods above (or is there any other?), I was hoping to get this question over to more experienced people out here who hopefully help make my decision.

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  • How to properly implement the Strategy pattern in a web MVC framework?

    - by jboxer
    In my Django app, I have a model (lets call it Foo) with a field called "type". I'd like to use Foo.type to indicate what type the specific instance of Foo is (possible choices are "Number", "Date", "Single Line of Text", "Multiple Lines of Text", and a few others). There are two things I'd like the "type" field to end up affecting; the way a value is converted from its normal type to text (for example, in "Date", it may be str(the_date.isoformat())), and the way a value is converted from text to the specified type (in "Date", it may be datetime.date.fromtimestamp(the_text)). To me, this seems like the Strategy pattern (I may be completely wrong, and feel free to correct me if I am). My question is, what's the proper way to code this in a web MVC framework? In a client-side app, I'd create a Type class with abstract methods "serialize()" and "unserialize()", override those methods in subclasses of Type (such as NumberType and DateType), and dynamically set the "type" field of a newly-instantiated Foo to the appropriate Type subclass at runtime. In a web framework, it's not quite as straightforward for me. Right now, the way that makes the most sense is to define Foo.type as a Small Integer field and define a limited set of choices (0 = "Number", 1 = "Date", 2 = "Single Line of Text", etc.) in the code. Then, when a Foo object is instantiated, use a Factory method to look at the value of the instance's "type" field and plug in the correct Type subclass (as described in the paragraph above). Foo would also have serialize() and unserialize() methods, which would delegate directly to the plugged-in Type subclass. How does this design sound? I've never run into this issue before, so I'd really like to know if other people have, and how they've solved it.

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  • How to limit setAccessible to only "legitimate" uses?

    - by polygenelubricants
    The more I learned about the power of setAccessible, the more astonished I am at what it can do. This is adapted from my answer to the question (Using reflection to change static final File.separatorChar for unit testing). import java.lang.reflect.*; public class EverythingIsTrue { static void setFinalStatic(Field field, Object newValue) throws Exception { field.setAccessible(true); Field modifiersField = Field.class.getDeclaredField("modifiers"); modifiersField.setAccessible(true); modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL); field.set(null, newValue); } public static void main(String args[]) throws Exception { setFinalStatic(Boolean.class.getField("FALSE"), true); System.out.format("Everything is %s", false); // "Everything is true" } } You can do truly outrageous stuff: public class UltimateAnswerToEverything { static Integer[] ultimateAnswer() { Integer[] ret = new Integer[256]; java.util.Arrays.fill(ret, 42); return ret; } public static void main(String args[]) throws Exception { EverythingIsTrue.setFinalStatic( Class.forName("java.lang.Integer$IntegerCache") .getDeclaredField("cache"), ultimateAnswer() ); System.out.format("6 * 9 = %d", 6 * 9); // "6 * 9 = 42" } } Presumably the API designers realize how abusable setAccessible can be, but must have conceded that it has legitimate uses to provide it. So my questions are: What are the truly legitimate uses for setAccessible? Could Java has been designed as to NOT have this need in the first place? What would the negative consequences (if any) of such design be? Can you restrict setAccessible to legitimate uses only? Is it only through SecurityManager? How does it work? Whitelist/blacklist, granularity, etc? Is it common to have to configure it in your applications?

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  • MySql "comments" parameter as descriptor?

    - by Nick
    So, I'm trying to learn a lot at once, and this place is really helpful! I'm making a little running log website for myself and maybe a few other people, and I have it so that the user can add workouts for each day. With each workout, I have a variety of information the user can fill out for the workout, such as running distance, time, quality of run, course, etc... I store this in a MySql database as a table with fields titled "distance", "time", "runquality", etc... Now, these field titles don't match up with what I want displayed on the running log, so I was thinking of using the "Comments" attribute for a field to store its human-readable title--thus the field "runquality" would have "Quality of run" as its comment, and then I would pull the comment with a SQL query and display it instead of the field name. Is this a good theoretical/practical way of going about it? And what sort of SQL would I use to pull the comment for the field anyway? Secondly, suppose I want to add the ability for the user to create their own workout descriptors. So say a user wants to add a "temperature" descriptor for their workout. Should I create a script that adds fields to my workout table, or should I create a separate table listing only workout descriptors and somehow link the descriptor table with the "contents" table? I haven't learned any theory about database design or anything so any help is appreciated!

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  • How to encapsulate a WinAPI application into a C++ class

    - by Semen Semenych
    There is a simple WinAPI application. All it does currently is this: register a window class register a tray icon with a menu create a value in the registry in order to autostart and finally, it checks if it's unique using a mutex As I'm used to writing code mainly in C++, and no MFC is allowed, I'm forced to encapsulate this into C++ classes somehow. So far I've come up with such a design: there is a class that represents the application it keeps all the wndclass, hinstance, etc variables, where the hinstance is passed as a constructor parameter as well as the icmdshow and others (see WinMain prototype) it has functions for registering the window class, tray icon, reigstry information it encapsulates the message loop in a function In WinMain, the following is done: Application app(hInstance, szCmdLIne, iCmdShow); return app.exec(); and the constructor does the following: registerClass(); registerTray(); registerAutostart(); So far so good. Now the question is : how do I create the window procedure (must be static, as it's a c-style pointer to a function) AND keep track of what the application object is, that is, keep a pointer to an Application around. The main question is : is this how it's usually done? Am I complicating things too much? Is it fine to pass hInstance as a parameter to the Application constructor? And where's the WndProc? Maybe WndProc should be outside of class and the Application pointer be global? Then WndProc invokes Application methods in response to various events.

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  • Structuring the UI code of a single-page EXTjs Web app using Rails?

    - by Daniel Beardsley
    I’m in the process of creating a large single-page web-app using ext-js for the UI components with Rails on the backend. I’ve come to good solutions for transferring data using Whorm gem and Rails support of RESTful Resources. What I haven’t come to a conclusion on is how to structure the UI and business logic aspects of the application. I’ve had a look at a few options, including Netzke but haven’t seen anything that I really think fits my needs. How should a web-application that uses ext-js components, layouts, and controls in the browser and Rails on the server best implement UI component re-use, good organization, and maintainability while maintaining a flexible layout design. Specifically I’m looking for best-practice suggestions for structuring the code that creates and configures UI components (many UI config options will be based on user data) Should EXT classes be extended in static JS for often re-used customizations and then instantiated with various configuration options by generated JS within html partials? Should partials create javascript blocks that instantiate EXT components? Should partials call helpers that return ruby hashes for EXT component config which is then dumped to Json? Something else entirely? There are many options and I'd love to hear from people who've been down this road and found some methodology that worked for them.

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