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  • Javascript object encapsulation that tracks changes

    - by Raynos
    Is it possible to create an object container where changes can be tracked Said object is a complex nested object of data. (compliant with JSON). The wrapper allows you to get the object, and save changes, without specifically stating what the changes are Does there exist a design pattern for this kind of encapsulation Deep cloning is not an option since I'm trying to write a wrapper like this to avoid doing just that. The solution of serialization should only be considered if there are no other solutions. An example of use would be var foo = state.get(); // change state state.update(); // or state.save(); client.tell(state.recentChange()); A jsfiddle snippet might help : http://jsfiddle.net/Raynos/kzKEp/ It seems like implementing an internal hash to keep track of changes is the best option. [Edit] To clarify this is actaully done on node.js on the server. The only thing that changes is that the solution can be specific to the V8 implementation.

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Design pattern suggestion

    - by Avinash
    Following is the problem statement. There are n numbers of match strings, If event A occurs and then in certain period of time event B occurs then I do not raise alarm. but if B do not occurs then i have to raise alarm. There can be multiple chain of events which defines whether to raise alarm or not.

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  • Design pattern: Polymorphism for list of objects

    - by ziang
    Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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  • Looking for nice Javascript/jQuery code for displaying large tables

    - by misha-moroshko
    I have an HTML table which may contain thousands of rows (number of columns is not a problem here). I would like to be able to browse this table easily and be able to do the following: Decide how many rows will be presented Jump to the next/previous X number of rows Scroll the table using the scroll bars to any desired line Be able to customize/extend easily this Javascript/jQuery code Has anyone seen something similar ? Thank you very much !

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  • MVC + Repository Pattern - Still depends on Data Model?

    - by Jack
    I've started a project for school in which I am using ASP.NET MVC 2 + LINQ2SQL, and a business layer so my UI doesnt interact with the DB directly. My question is this: In my MVC project, when bringing up views and passing around data, I still have to include my Data project for access to the classes in my Linq2Sql project. Is this correct? Example: Controller: ClassesRepository cr = new ClassesRepository(); // this is from my Business project Class classToEdit = cr.GetByClassId(id); // "Class" is from my data project I still have to reference the Class class in my linq2sql data project - shouldn't my UI be completely independent of my data layer? Or maybe I'm going about this all wrong.

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  • Reducing lag when downloading large amount of data from webpage

    - by Mahir
    I am getting data via RSS feeds and displaying each article in a table view cell. Each cell has an image view, set to a default image. If the page has an image, the image is to be replaced with the image from the article. As of now, each cell downloads the source code from the web page, causing the app to lag when I push the view controller and when I try scrolling. Here is what I have in the cellForRowAtIndexPath: method. NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; cell.picture.image = image; Someone suggested using NSOperationQueue. Would this way be a good solution? EDIT: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *MyIdentifier = @"FeedCell"; LMU_LAL_FeedCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier]; if (cell == nil) { NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"LMU_LAL_FeedCell" owner:self options:nil]; cell = (LMU_LAL_FeedCell*) [nib objectAtIndex:0]; } int storyIndex = [indexPath indexAtPosition: [indexPath length] - 1]; NSString *untrimmedTitle = [[stories objectAtIndex: storyIndex] objectForKey: @"title"]; cell.title.text = [untrimmedTitle stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; CGSize maximumLabelSize = CGSizeMake(205,9999); CGSize expectedLabelSize = [cell.title.text sizeWithFont:cell.title.font constrainedToSize:maximumLabelSize]; //adjust the label to the the new height. CGRect newFrame = cell.title.frame; newFrame.size.height = expectedLabelSize.height; cell.title.frame = newFrame; //position frame of date label CGRect dateNewFrame = cell.date.frame; dateNewFrame.origin.y = cell.title.frame.origin.y + cell.title.frame.size.height + 1; cell.date.frame = dateNewFrame; cell.date.text = [self formatDateAtIndex:storyIndex]; dispatch_queue_t someQueue = dispatch_queue_create("cell background queue", NULL); dispatch_async(someQueue, ^(void){ NSError *error = nil; NSString * storyLink = [[stories objectAtIndex: storyIndex] objectForKey: @"link"]; storyLink = [storyLink stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *sourceCode = [NSString stringWithContentsOfURL:[NSURL URLWithString:storyLink] encoding:NSUTF8StringEncoding error:&error]; NSString *startPt = @"instant-gallery"; NSString *startPt2 = @"<img src=\""; if ([sourceCode rangeOfString:startPt].length != 0) { //webpage has images // find the first "<img src=...>" tag starting from "instant-gallery" NSString *trimmedSource = [sourceCode substringFromIndex:NSMaxRange([sourceCode rangeOfString:startPt])]; trimmedSource = [trimmedSource substringFromIndex:NSMaxRange([trimmedSource rangeOfString:startPt2])]; trimmedSource = [trimmedSource substringToIndex:[trimmedSource rangeOfString:@"\""].location]; NSURL *url = [NSURL URLWithString:trimmedSource]; NSData *data = [NSData dataWithContentsOfURL:url]; UIImage *image = [UIImage imageWithData:data]; dispatch_async(dispatch_get_main_queue(), ^(void){ cell.picture.image = image; }); }) //error: expected expression } return cell; //error: expected identifier } //error extraneous closing brace

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  • Locking DB w/ Large Reads (Ruby-on-Rails/Heroku)

    - by Splashlin
    Currently I have a Web API running on Heroku that is constantly writing information we're collecting from other data sources (currently theres about half a GB of data and it's growing very quickly). We're looking to add a reporting system on top of the current database that we can use to extract useful information out of the DB. The problem is that when we're running reports we're locking the DB and any other sites communicating with the DB are timing out. Does anyone have any solutions on how to solve this type of issue? Amazon RDS seems to have some interesting stuff with database replication but I don't know if that will solve my problems. Any advice would be greatly appreciated. Thanks

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  • Design pattern for data entry forms with LINQ2SQL

    - by petebob796
    I am about to start a new winforms data entry application, it already has the database designed which I am comfortable with. I was going to use LINQ2SQL to access the tables to keep things type safe but am now wondering about design patterns, something I am just getting into. Since LINQ is giving me objects to use should I still create classes in between to hold the validation code and helper methods or should these just go in with the UI? It just seems I will end up with classes sat in between with little code which will cause the UI classes to have code just getting and setting values in the intermediate class and returning from validation to flag errors... Any good reading on this? Should I consider the entity framework (or similar) instead?

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  • Getting the Item Count of a large sharepoint list in fastest way

    - by sooraj
    I am trying to get the count of the items in a sharepoint document library programatically. The scale I am working with is 30-70000 items. We have usercontrol in a smartpart to display the count . Ours is a TEAM site. This is the code to get the total count SPList VoulnterrList = web.Lists[ListTitle]; SPQuery query = new SPQuery(); query.ViewAttributes = "Scope=\"Recursive\""; string queries = "<Where><Eq><FieldRef Name='ApprovalStatus' /><Value Type='Choice'>Pending</Value></Eq></Where>"; query.Query = queries; SPListItemCollection lstitemcollAssoID = VoulnterrList.GetItems(query); lblCount.Text = "Total Proofs: " + VoulnterrList.Items.Count.ToString() + " Pending Proofs: " + lstitemcollAssoID.Count.ToString(); The problem is this has serious performance issue it takes 75 to 80 sec to load the page. if we comment this page load will decrees to 4 sec. Any better approch for this problem Ours is sharepoint 2007

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  • Java combine parents of two large inheritance chains

    - by Soylent Green
    I have two parent classes in a huge project, let's say ClassA and ClassB. Each class has many subclasses, which in turn have many subclasses, which in turn have many subclasses, etc. My task is to "marry" these two "families" so that both inherit from a SINGLE parent. I need to essentially make ClassA and ClassB one class (parent) to both of their combined subclasses (children). ClassA and ClassB both currently implement Serializable. I am currently trying to make both inheritance chains inherit from ClassA, and then copy all functions and data members from ClassB into ClassA. This is tedious, and I think a terrible solution. What would be the CORRECT way to solve this problem?

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  • Design pattern for loading multiple message types

    - by lukem00
    As I was looking through SO I came across a question about handling multiple message types. My concern is - how do I load such a message in a neat way? I decided to have a separate class with a method which loads one message each time it's invoked. This method should create a new instance of a concrete message type (say AlphaMessage, BetaMessage, GammaMessage, etc.) and return it as a Message. class MessageLoader { public Message Load() { // ... } } The code inside the method is something which looks really awful to me and I would very much like to refactor it/get rid of it: Message msg = Message.Load(...); // load yourself from whatever source if (msg.Type == MessageType.Alpha) return new AlphaMessage(msg); if (msg.Type == MessageType.Beta) return new BetaMessage(msg); // ... In fact, if the whole design looks just too messy and you guys have a better solution, I'm ready to restructure the whole thing. If my description is too chaotic, please let me know what it's missing and I shall edit the question. Thank you all.

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  • how to handle large dataset like sproutcore

    - by Nik
    Hello all, I really don't have any substantial code to show here, actually, that's kinda why I am writing: I looked at the SproutCore demo, especially the Collection demo, on http://demo.sproutcore.com/sample_controls/, and am amazed by its loading 200,000 records to the page so easily. I tried using Rails to provide 200,000 records and in a completely blank HTML page with <% @projects.each do |p| % <%= p.title % <% end % that freezes the browser for seconds on my m1530 laptop with 4gb ram and t7700 256gb ssd. Yet the sproutcore demo does not freeze and takes less than 3 seconds to load. What do you think the one technique they are using to enable this is? Thanks!

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  • Pass object from webserver to client

    - by user362914
    I developed a C# web application that calls a web-service which returns a base64 encoded array (PDF file). I then convert that array into a UCOMIStream object (I know it is obsolete, but the DLL that I am using requires it as a parameter). I use the following code to do the conversion which works perfectly. I can pass this object to the DLL so that I can print the PDF. This works great on the Webserver, but the requirement is to print it locally. Byte[] bBuffer = statementOut.statementcycle.statementdata.content; int size = bBuffer.Length; IntPtr mem = Marshal.AllocHGlobal(size); Marshal.Copy(bBuffer, 0, mem, size); // Create an OLE Stream object. System.Runtime.InteropServices.UCOMIStream str; //obsolete but the createstreamonhglobal outputs it CreateStreamOnHGlobal(mem, true, out str); The DLL resides on the client so I am able to use ActiveX to create the object using javascript and/or VBscript;however, I have not been able to figure out how to get the stream object to the client to pass to the DLL. How can this be achieved?

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  • Looking for an appropriate design pattern

    - by user1066015
    I have a game that tracks user stats after every match, such as how far they travelled, how many times they attacked, how far they fell, etc, and my current implementations looks somewhat as follows (simplified version): Class Player{ int id; public Player(){ int id = Math.random()*100000; PlayerData.players.put(id,new PlayerData()); } public void jump(){ //Logic to make the user jump //... //call the playerManager PlayerManager.jump(this); } public void attack(Player target){ //logic to attack the player //... //call the player manager PlayerManager.attack(this,target); } } Class PlayerData{ public static HashMap<int, PlayerData> players = new HashMap<int,PlayerData>(); int id; int timesJumped; int timesAttacked; } public void incrementJumped(){ timesJumped++; } public void incrementAttacked(){ timesAttacked++; } } Class PlayerManager{ public static void jump(Player player){ players.get(player.getId()).incrementJumped(); } public void incrementAttacked(Player player, Player target){ players.get(player.getId()).incrementAttacked(); } } So I have a PlayerData class which holds all of the statistics, and brings it out of the player class because it isn't part of the player logic. Then I have PlayerManager, which would be on the server, and that controls the interactions between players (a lot of the logic that does that is excluded so I could keep this simple). I put the calls to the PlayerData class in the Manager class because sometimes you have to do certain checks between players, for instance if the attack actually hits, then you increment "attackHits". The main problem (in my opinion, correct me if I'm wrong) is that this is not very extensible. I will have to touch the PlayerData class if I want to keep track of a new stat, by adding methods and fields, and then I have to potentially add more methods to my PlayerManager, so it isn't very modulized. If there is an improvement to this that you would recommend, I would be very appreciative. Thanks.

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  • hadoop - large database query

    - by Mastergeek
    Situation: I have a Postgres DB that contains a table with several million rows and I'm trying to query all of those rows for a MapReduce job. From the research I've done on DBInputFormat, Hadoop might try and use the same query again for a new mapper and since these queries take a considerable amount of time I'd like to prevent this in one of two ways that I've thought up: 1) Limit the job to only run 1 mapper that queries the whole table and call it good. or 2) Somehow incorporate an offset in the query so that if Hadoop does try to use a new mapper it won't grab the same stuff. I feel like option (1) seems more promising, but I don't know if such a configuration is possible. Option(2) sounds nice in theory but I have no idea how I would keep track of the mappers being made and if it is at all possible to detect that and reconfigure. Help is appreciated and I'm namely looking for a way to pull all of the DB table data and not have several of the same query running because that would be a waste of time.

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  • Breaking up large DataGridView for printing

    - by Hal
    Hey, I've got a single-row, 40 column-long DataGridView that i need to print. Since i can neither print it directly (because A4 sheets won't cut it ;)) nor adjust its width to the width of the page itself (because the headers look terrible), i wanted to break the DataGridView to 4 separate pieces and display 10 columns per row (imagine: column 1 to 10 in the first line, column 11 to 21 four or five lines below, etc...). Is there an easy way to do this? I was leaning towards a more manual approach (using fors), but i'd love to know if there's a more elegant way. Cheers

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  • Sed-replacing a pattern

    - by grails_enthu
    I have below code: <td nowrap="nowrap" width="74"> <p align="center">server1</p> </td> <td nowrap="nowrap" width="74"> <p align="center">server2</p> </td> and so on.I want to get output as: <td nowrap="nowrap" width="74">server1</td> <td nowrap="nowrap" width="74">server2</td> What should be my approach?Say for example the file is server.html I have done something like this: sed "s/<p align="center">*</p>/*/" -i server.html But its not working.

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  • Ideal way/architecture to deliver large data over Web Services

    - by zengr
    We are trying to design 6 web services, which will serve another client component. The client component requires data from the web service we are implementing. Now, the problem is, there is not 1 WS we are implementing, there is one WS which the client component hits, this initiates a series (5 more) of WSs which gather data from their respective data stores and finally provide the data back to the original WS, which then delivers the data back to the client component. So, if the requested data becomes huge, then, this will be a serious problem for our internal communication channel. So, what do you guys suggest? What can be done to avoid overloading of the communication channel between the internal WS and at the same time, also delivering the data to the client component.

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  • Large Table in iFrame crashes IE8

    - by Brian
    I have a page with an iFrame whose source is an ashx page. The handler takes in 3 arguments through the query string and generates a text/html response containing a table. When the table gets 1700 rows it crashes the IE8 browser. The browser freezes and returns a null reference error. If I take the html that is being rendered and place it inside a DIV on the page it renders fine in IE8. Any suggestions?

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  • String Object. Clarification needed

    - by mac
    Guys, help me clarify. Say i have the following line in my program: jobSetupErrors.append("abc"); In the case above where jobSetupErrors is a StringBuilder(), what i see happen is: New String Object is created and assigned value "abc" value of that String object is assigned to the existing StringBuilder object If that is correct, and I add 1 more line ... jobSetupErrors.append("abc"); logger.info("abc"); In the above example are we creating String object separately 2 times? If so, would it be more proper to do something like this? String a = "abc"; jobSetupErrors.append(a); logger.info(a); Is this a better approach? Please advise

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