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• When should I use a struct instead of a class?

  - by Esteban Araya

  MSDN says that you should use structs when you need lightweight objects. Are there any other scenarios when a struct is preferable over a class? Edit: Some people have forgotten that: 1. structs can have methods! 2. structs have no inheritance capabilites. Another Edit: I understand the technical differences, I just don't have a good feel for WHEN to use a struct.

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• Rowwise iteration of a dictionay object

  - by mono

  I have a dictionary object like: Dictionary<string, HashSet<int>> dict = new Dictionary<string, HashSet<int>>(); dict.Add("foo", new HashSet<int>() { 15,12,16,18}); dict.Add("boo", new HashSet<int>() { 16,47,45,21 }); I have to print in such a way such that result would be as following at each iteration: It1: foo boo //only the key in a row It2: 15 16 It3: 16 47 Can anyone help me to achieve this. Thanks.

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• android, find the nearest location without going through all the locations

  - by Marwan

  I am building a taxi dispatching app first: I need the passenger app to show the nearest taxis, now I know how to do that in code but in my way I have to go through all the taxis locations(in database on server) and calculate the distance from the passenger location and get the lowest ones - I don't want to do this because there will be a lot of taxis and going through all of them and making some math is kind of pain on the server- is there a way to get the nearest ones without going through all of them? second: what the best database to use - first, should it be sql or non-sql - I need a very robust database, because there will be a lot of updates (I mean the passengers locations added then deleted when arriving to destination && the taxis location changes frequently) finally: I will use RubyOnRails to do the server side and json as data transfer format, do you have a recommendation to me on something better? Thanks

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• Inheritence and usage of dynamic_cast

  - by Mewzer

  Hello, Suppose I have 3 classes as follows (as this is an example, it will not compile!): class Base { public: Base(){} virtual ~Base(){} virtual void DoSomething() = 0; virtual void DoSomethingElse() = 0; }; class Derived1 { public: Derived1(){} virtual ~Derived1(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD1DoSomething{ ... } }; class Derived2 { public: Derived2(){} virtual ~Derived2(){} virtual void DoSomething(){ ... } virtual void DoSomethingElse(){ ... } virtual void SpecialD2DoSomething{ ... } }; I want to create an instance of Derived1 or Derived2 depending on some setting that is not available until run-time. As I cannot determine the derived type until run-time, then do you think the following is bad practice?... class X { public: .... void GetConfigurationValue() { .... // Get configuration setting, I need a "Derived1" b = new Derived1(); // Now I want to call the special DoSomething for Derived1 (dynamic_cast<Derived1*>(b))->SpecialD1DoSomething(); } private: Base* b; }; I have generally read that usage of dynamic_cast is bad, but as I said, I don't know which type to create until run-time. Please help!

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• Turn database result into array

  - by Industrial

  Hi everyone, I have just made the update/add/delete part for the "Closure table" way of organizing query hierarchical data that are shown on page 70 in this slideshare: http://www.slideshare.net/billkarwin/sql-antipatterns-strike-back My database looks like this: Table Categories: ID Name 1 Top value 2 Sub value1 Table CategoryTree: child parent 1 1 2 2 2 1 However, I have a bit of an issue getting the full tree back as an multidimensional array from a single query. Here's what I would like to get back: array ( 'topvalue' = array ( 'Subvalue', 'Subvalue2', 'Subvalue3' = array ('Subvalue 1', 'Subvalue 2', 'Subvalue 3' ) ); ); Update: Found this link, but I still have a hard time to convert it into an array: http://karwin.blogspot.com/2010/03/rendering-trees-with-closure-tables.html

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• Sort database entries via a dropdown list

  - by Lin

  Hello! I'm curious if anyone could possibly help me, because I can't find anything exactly related to it anywhere, and it's driving me nuts. I'd like to have a dropdown list on a page, that will give the visitor the option to sort all entries by year. I have entries from i.e. 2001, 2005, 2009, 2010. The years should be displayed in the dropdown, so the visitor can easily just select all entries dated 2001 if they want. The year for each entry is located in the one database table I have. In other words, I simply want a "sort by" dropdown that you can see on pretty much any shopping site nowadays. But with set years. Thanks in advance for any replies!

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• Re-usable Obj-C classes with custom values: The right way

  - by Prairiedogg

  I'm trying to reuse a group of Obj-C clases between iPhone applications. The values that differ from app to app have been isolated and I'm trying to figure out the best way to apply these custom values to the classes on an app-to-app basis. Should I hold them in code? // I might have 10 customizable values for each class, that's a long signature! CarController *controller = [[CarController alloc] initWithFontName:@"Vroom" engine:@"Diesel" color:@"Red" number:11]; Should I store them in a big settings.plist? // Wasteful! I sometimes only use 2-3 of 50 settings! AllMyAppSettings *settings = [[AllMyAppSettings alloc] initFromDisk:@"settings.plist"]; MyCustomController *controller = [[MyCustomController alloc] initWithSettings:settings]; [settings release]; Should I have little, optional n_settings.plists for each class? // Sometimes I customize CarControllerSettings *carSettings = [[CarControllerSettings alloc] initFromDisk:@"car_settings.plist"]; CarController *controller = [[CarController alloc] initWithSettings:carSettings]; [carSettings release]; // Sometimes I don't, and CarController falls back to internally stored, reasonable defaults. CarController *controller = [[CarController alloc] initWithSettings:nil]; Or is there an OO solution that I'm not thinking of at all that would be better?

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• What's the recommended way to declare fields of a class in JavaScript?

  - by Bytecode Ninja

  Is it better to declare fields of a class in this way: function MyClass() { this.aMethod = function() { // code } } Or this way: function MyClass() { } MyClass.prototype.aMethod = function() { // code } Any why? Thanks in advance.

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• Custom link on embedded youtube video

  - by 0plus1

  I'm looking to direct the user on the channell webpage instead of the video url that I'm embedding. I've read the api and I didn't see any way to achieve this. I tried enclosing the embedded video in a and I added this code: $('#youtube').click(function() { document.write('http://www.youtube.com/user/trasportareoggi'); return false; }); And surprise it won't work. How, if it's even possible I can do this?

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• Custom business object comparer

  - by gruber

  Hello, I need to implement mechanism that compares two business objects and return the list of differences (past value, new value, isDifferenceBetter). Because not all fields of class has to be compared and one fields need to be compared with different function then the other (sometimes < is better sometimes is better ... ) I figured out that I need to implelemnt custom attribute and give it to each field that has to be compared in this object. This attribute must have: - name - delegate or sth to point to the function which would be applied for comparision (dont know how to do it so far) So could anyone suggest me if its a good idea? Maybe any other ideas. Using attributes I would be able to use refflection to iterate through each field with attribute and invoke needed delegate. thanks for help bye

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• Rails: Ajax-enabled form without a model object

  - by Caffeine Coma

  I'm new to Rails and having a hard time figuring out how to create a form that submits over Ajax without having a corresponding model object. My use case is a simple form that collects an email address and sends it an email; there's nothing to be persisted, so no model. In cases where I do have a model, I've had success with form_for(@model, remote: true). I can't seem to find the right helper for the case where there is no model. I tried form_tag(named_path, remote: true) and that works, but does not use Ajax. Pointers to an example with an example with a proper controller, .html.erb and routes.rb would be really appreciated.

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• Creating an AJAX Form for a Polymorphic Object in Rails

  - by Isaac Yerushalmi

  I am trying to create an AJAX form for a polymorphic associated model. I created "Comments" which have a polymorphic association with all objects you can comment on (i.e. user profiles, organization profiles, events, etc). I can currently add comments to objects using a form created by: form_for [@commentable, @comment] do |f| I am trying to make this form via Ajax but I keep getting errors. I've tried at least ten different pieces of code, using remote_form_tag, remote_form_for, etc..with all different options, and nothing works. The comment does not get inserted into the database. Can anyone please tell me how I can make the above form ajax-enabled?

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• Find by include nil object error in rails

  - by SpyrosP

  I've been trying hard to solve this problem but i really don't know what is happening. I have this small piece of code : DiscoveredLocation.find_by_user_id(user.id, :include => [:boss_kills]) The models are : DiscoveredLocation(id, user_id, boss_location_id) BossKill(user_id, monster_id) and associations : Monster belongs_to :boss_location Monster has_many :boss_kills BossKill belongs_to :user BossKill belongs_to :monster DiscoveredLocation belongs_to :user DiscoveredLocation belongs_to :boss_location DiscoveredLocation has_many :monsters, :through => :boss_location DiscoveredLocation has_many :boss_kills, :through => :monsters When i executed the find_by i get this error : NoMethodError in BossesController#index You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.each If i change the include option to any other model, like :monster, it works great. I'm pretty much owned by this problem :P. Maybe somebody can help me ? :)

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• How to properly name classes inside a domain namespace?

  - by devoured elysium

  Let's say I'm trying to implement a Chess Game. I'd create my Chess classes in a Chess namespace. Now, should I prefix all my Chess related classes with the Chess word, or as they are already inside that namespace, should I just call them by what they are? Example: ChessGame vs Game ChessPiece vs Piece

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• JavaScript using toString on a Function object to read text content

  - by mseeley

  Calling toString() on the function below returns different strings across browsers. I understand this is because ECMA-262 15.3.4.2 leaves wiggle room for each vendor. Chrome returns the comments in addition to all syntax. Sadly Firefox 3.6 omits the comments. Based on Firefox's behavior I haven't tested IE, Opera, or Safari. function foo() { /* comment */ var bar = true; } Specifically, I am attempting to embed meta data within a specially formatted comment block within a function. Later the return value of the functions toString() method would be parsed and values returned as an object. I've been unable to locate compatibility tables or alternatives to toString(). Does the community have any ideas? Btw, pre-processing JS files isn't an option. :( Thanks a lot. :)

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• Archiving Database Tables using Java

  - by HonorGod

  My application demands archiving database tables between sybase and db2 and vice-a-versa and within(db2 to db2 and sybase to sybase) using java. I am trying to understand the best strategies around in terms performance, implementation, ease of use and scalability. Here is my current process - source and destination tables with the acceptable parameters (from java) are defined within xml. the application reads the source and destination configurations and execute them sequentially. destination is sometime optional when source is just deleting data from a specific table or when the source is just calling a stored procedure. dataset between source and destination is extremely large (in millions) From top of my head, it looks like I can define dependencies between multiple source and destination combination and have them execute in parallel in multiple treads. But will this improve any performance(i hope it will)? Are there any open-source frameworks for data archiving using java? Any other thoughts on the implements side will be really helpful. Thanks

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• What Patterns Should I Consider For a Html Widget Generator?

  - by DaveDev

  I'm looking to see if I can design a HtmlHelper extension method that will generate the Html for different types of widgets I want to produce. Each different type of widget implements functionality to get and prepare any data it needs to render. Can anyone suggest any patterns I could refer to for approaches to take? I know there are probably frameworks available that will do this for me, but I thought I'd give it a try anyway. Any points of advice? Thanks

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• Replace singletons with what?

  - by fig-gnuton

  Singletons are so often said to be a bad design choice, so how should you design an application when you want to avoid them?

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• When to define SDD operations System->Actor?

  - by devoured elysium

  I am having some trouble understanding how to make SDDs, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The user tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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• Want to understand C++ sentry object

  - by Romain Hippeau

  I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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• Loading large amounts of data to an Oracle SQL Database

  - by James

  Hey all, I was wondering if anyone had any experience with what I am about to embark on. I have several csv files which are all around a GB or so in size and I need to load them into a an oracle database. While most of my work after loading will be read-only I will need to load updates from time to time. Basically I just need a good tool for loading several rows of data at a time up to my db. Here is what I have found so far: I could use SQL Loader t do a lot of the work I could use Bulk-Insert commands Some sort of batch insert. Using prepared statement somehow might be a good idea. I guess I was wondering what everyone thinks is the fastest way to get this insert done. Any tips?

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• Pattern for iPhone background loading during init?

  - by Rob S.

  Hi everyone, I'm currently kicking off a background thread to do some REST queries in my app delegate's didFinishLaunchingWithOptions. This thread creates some objects and populates the model as the rest of the app continues to load (because I don't block, and didFinishLaunchingWithOptions returns YES). I also put up a loading UIViewController 'on top' of the main view that I tear down after the background initialization is complete. My problem is that I need to notify the first view (call it the Home view) that the model is ready, and that it should populate itself. The trick is that the background download could have finished before Home.viewDidAppear is called, or any of the other Home.initX methods. I'm having difficulty synchronizing all of this and I've thought about it long enough that it feels like I'm barking up the wrong tree. Are there any patterns here for this sort of thing? I'm sure other apps start by performing lengthy operations with loading screens :) Thanks!

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• Using request.setAttribute in a JSP page

  - by ria

  Is it possible to use request.setAttribute on a JSP page and then on HTML Submit get the same request attribute in the Servlet?

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• Storing Object Types in Variable then Initializing

  - by Jon Mattingly

  Is there a way in Objective-C to store an object/class in a variable to be passed to alloc/init somewhere else? For example: UIViewController = foo foo *bar = [[foo alloc] init] I'm trying to create a system to dynamically create navigation buttons in a separate class based on the current view controller. I can pass 'self' to the method, but the variable that results does not allow me to alloc/init. I could always import the .h file directly, but ideally I would like to make reusing the code as simple as possible. Maybe I'm going about this the wrong way?

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• How to connect to foreign DB2 database using Python (Ubuntu)

  - by dblips

  sudo easy_install ibm_db-1.0.1-py2.5-linux-i686.egg only works after sudo apt-get install python-dev. Some troubles to find that out in the first place ... Downloaded from IBM site v9.5fp5_linuxia32_dsdriver.tar.gz and pointing IBM_DB_DIR and IBM_DB_LIB to the clidriver(/lib) dir -- is this needed/correct one? -- libdb2.so(.1) is in there... Nevertheless: >>> import ibm_db Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: libdb2.so.1: cannot open shared object file: No such file or directory Any help is very much appreciated!

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