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  • Formal name of Magento’s Class Override Design Pattern?

    - by Alan Storm
    Magento is a newish (past 5 years) PHP based Ecommerce system with an architecture that's similar to the Java Spring framework (or so I've been told) One of the features of the Framework is certain classes are not directly instantiated. Rather than do something like $model = new Mage_Foo_Model_Name(); you pass an identifier into a static method on a global application object $model = Mage::getModel('foo/name'); and this instantiates the class for you. One of the wins with this approach is getModel checks a global configuration system for the foo/name identifier, and instantiates the class name it finds in the configuration system. This allows you to change the behavior of a Model system wide with a single configuration change. Is there a formal, Gang of Four or otherwise, name that describes this system/design pattern? The instantiation itself looks like a classic Factory pattern, but I'm specifically interested in the whole "override a class in the system via configuration" aspect. Is there a name/concept that covers this, or is it contained within the worldview of a Factory?

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  • correct technical term for this pattern

    - by Oliver A.
    sometimes I use a pattern which is very similar to the singleton pattern: There is one default instance which and a static get method to aces it. But you may create other instances and pass it as optional parameter and if you want to and you can even replace the default instance with a instance from a child class. So it is NO SINGLETON at all but it is used like one singleton in most cases. Anyone got an idea who to call something like this ? Maybe half*** singleton? domiton?

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  • GridView: Control Designer

    - by pipelinecache
    Hi, I have a question regarding the GridView and the Control Designer of it. I've made a composite control inherited of the GridView. I would like to make some new created BoundField controls available in the designer of the GridView control? So that I can select the custom BoundField control from the Available fields list. Anyone got a clue about this one?

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  • User oriented regex library for java

    - by Maxim Veksler
    Hello, I'm looking for a library that could perform "easy" pattern matching, a kind of pattern that can be exposed via GUI to users. It should define a simple matching syntax like * matches any char and alike. In other words, I want to do glob (globbing) like sun's implemented logic http://openjdk.java.net/projects/nio/javadoc/java/nio/file/PathMatcher.html but without relation to the file system. Ideas?

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  • Optimizing a lot of Scanner.findWithinHorizon(pattern, 0) calls

    - by darvids0n
    I'm building a process which extracts data from 6 csv-style files and two poorly laid out .txt reports and builds output CSVs, and I'm fully aware that there's going to be some overhead searching through all that whitespace thousands of times, but I never anticipated converting about about 50,000 records would take 12 hours. Excerpt of my manual matching code (I know it's horrible that I use lists of tokens like that, but it was the best thing I could think of): public static String lookup(List<String> tokensBefore, List<String> tokensAfter) { String result = null; while(_match(tokensBefore)) { // block until all input is read if(id.hasNext()) { result = id.next(); // capture the next token that matches if(_matchImmediate(tokensAfter)) // try to match tokensAfter to this result return result; } else return null; // end of file; no match } return null; // no matches } private static boolean _match(List<String> tokens) { return _match(tokens, true); } private static boolean _match(List<String> tokens, boolean block) { if(tokens != null && !tokens.isEmpty()) { if(id.findWithinHorizon(tokens.get(0), 0) == null) return false; for(int i = 1; i <= tokens.size(); i++) { if (i == tokens.size()) { // matches all tokens return true; } else if(id.hasNext() && !id.next().matches(tokens.get(i))) { break; // break to blocking behaviour } } } else { return true; // empty list always matches } if(block) return _match(tokens); // loop until we find something or nothing else return false; // return after just one attempted match } private static boolean _matchImmediate(List<String> tokens) { if(tokens != null) { for(int i = 0; i <= tokens.size(); i++) { if (i == tokens.size()) { // matches all tokens return true; } else if(!id.hasNext() || !id.next().matches(tokens.get(i))) { return false; // doesn't match, or end of file } } return false; // we have some serious problems if this ever gets called } else { return true; // empty list always matches } } Basically wondering how I would work in an efficient string search (Boyer-Moore or similar). My Scanner id is scanning a java.util.String, figured buffering it to memory would reduce I/O since the search here is being performed thousands of times on a relatively small file. The performance increase compared to scanning a BufferedReader(FileReader(File)) was probably less than 1%, the process still looks to be taking a LONG time. I've also traced execution and the slowness of my overall conversion process is definitely between the first and last like of the lookup method. In fact, so much so that I ran a shortcut process to count the number of occurrences of various identifiers in the .csv-style files (I use 2 lookup methods, this is just one of them) and the process completed indexing approx 4 different identifiers for 50,000 records in less than a minute. Compared to 12 hours, that's instant. Some notes (updated): I don't necessarily need the pattern-matching behaviour, I only get the first field of a line of text so I need to match line breaks or use Scanner.nextLine(). All ID numbers I need start at position 0 of a line and run through til the first block of whitespace, after which is the name of the corresponding object. I would ideally want to return a String, not an int locating the line number or start position of the result, but if it's faster then it will still work just fine. If an int is being returned, however, then I would now have to seek to that line again just to get the ID; storing the ID of every line that is searched sounds like a way around that. Anything to help me out, even if it saves 1ms per search, will help, so all input is appreciated. Thankyou! Usage scenario 1: I have a list of objects in file A, who in the old-style system have an id number which is not in file A. It is, however, POSSIBLY in another csv-style file (file B) or possibly still in a .txt report (file C) which each also contain a bunch of other information which is not useful here, and so file B needs to be searched through for the object's full name (1 token since it would reside within the second column of any given line), and then the first column should be the ID number. If that doesn't work, we then have to split the search token by whitespace into separate tokens before doing a search of file C for those tokens as well. Generalised code: String field; for (/* each record in file A */) { /* construct the rest of this object from file A info */ // now to find the ID, if we can List<String> objectName = new ArrayList<String>(1); objectName.add(Pattern.quote(thisObject.fullName)); field = lookup(objectSearchToken, objectName); // search file B if(field == null) // not found in file B { lookupReset(false); // initialise scanner to check file C objectName.clear(); // not using the full name String[] tokens = thisObject.fullName.split(id.delimiter().pattern()); for(String s : tokens) objectName.add(Pattern.quote(s)); field = lookup(objectSearchToken, objectName); // search file C lookupReset(true); // back to file B } else { /* found it, file B specific processing here */ } if(field != null) // found it in B or C thisObject.ID = field; } The objectName tokens are all uppercase words with possible hyphens or apostrophes in them, separated by spaces. Much like a person's name. As per a comment, I will pre-compile the regex for my objectSearchToken, which is just [\r\n]+. What's ending up happening in file C is, every single line is being checked, even the 95% of lines which don't contain an ID number and object name at the start. Would it be quicker to use ^[\r\n]+.*(objectname) instead of two separate regexes? It may reduce the number of _match executions. The more general case of that would be, concatenate all tokensBefore with all tokensAfter, and put a .* in the middle. It would need to be matching backwards through the file though, otherwise it would match the correct line but with a huge .* block in the middle with lots of lines. The above situation could be resolved if I could get java.util.Scanner to return the token previous to the current one after a call to findWithinHorizon. I have another usage scenario. Will put it up asap.

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  • List/Grid Toggle for Photo Gallery with Shadowbox

    - by InfamouslyBubbly
    so I'm new to this site, and new to jquery, and javascript as a whole really, but I have very good comprehension of HTML and CSS. For a class in school, I'm making a photo gallery webpage using the Shadowbox plugin. I have that part all down, but one of the requirements is to add some sort of user option that the user can change that will get saved in a cookie. (I haven't gotten to the cookie part yet) For my option, I decided to add a toggle that will switch the view of the page from a grid view (default) with images, to a list view of just the captions of the images. I figured out how to do that, but decided it could probably done in a much simpler fashion with the use of loops. Here is the HTML I have: <body> <div id="preferences"> <h1>My Photo Gallery</h1> <ul id="options"> <li><a href="#" id="list"><img src="media/listview.png" alt="List view"/></a></li> <li><a href="#" id="grid"><img src="media/gridview.png" alt="List view"/></a></li> </ul> </div> <div id="gallery"> <a rel="shadowbox[Gallery]" class="l1 img" href="media/img1.jpg" title="Black and White Leopard Pattern"><img src="media/thumb1.jpg" alt="Black and White Leopard Pattern"/></a> <a rel="shadowbox[Gallery]" class="l2 img" href="media/img2.jpg" title="Snow Leopard Pattern"><img src="media/thumb2.jpg" alt="Snow Leopard Pattern"/></a> <a rel="shadowbox[Gallery]" class="l3 img" href="media/img3.jpg" title="Colorful Triangle Pattern"><img src="media/thumb3.jpg" alt="Colurful Triangle Pattern"/></a> <a rel="shadowbox[Gallery]" class="l4 img" href="media/img4.jpg" title="Tie Dye Zebra Stripe Pattern"><img src="media/thumb4.jpg" alt="Tie Dye Zebra Stripe Pattern"/></a> <a rel="shadowbox[Gallery]" class="l5 img" href="media/img5.jpg" title="Blue Knitted Pattern"><img src="media/thumb5.jpg" alt="Blue Knitted Pattern"/></a> <a rel="shadowbox[Gallery]" class="l6 img" href="media/img6.jpg" title="Black and White Damask Pattern"><img src="media/thumb6.jpg" alt="Black and White Damask Pattern"/></a> <a rel="shadowbox[Gallery]" class="l7 img" href="media/img7.jpg" title="Wooden Panel Pattern"><img src="media/thumb7.jpg" alt="Wooden Panel Pattern"/></a> <a rel="shadowbox[Gallery]" class="l8 img" href="media/img8.jpg" title="Brick Pattern"><img src="media/thumb8.jpg" alt="Brick Pattern"/></a> <a rel="shadowbox[Gallery]" class="l9 img" href="media/img9.jpg" title="Watercolor Pattern"><img src="media/thumb9.jpg" alt="Watercolor Pattern"/></a> <a rel="shadowbox[Gallery]" class="l10 img" href="media/img10.jpg" title="Orange Stripe Pattern"><img src="media/thumb10.jpg" alt="Orange Stripe Pattern"/></a> <a rel="shadowbox[Gallery]" class="l11 img" href="media/img11.jpg" title="Blue Scales Pattern"><img src="media/thumb11.jpg" alt="Blue Scales Pattern"/></a> <a rel="shadowbox[Gallery]" class="l12 img" href="media/img12.jpg" title="Woven Pattern"><img src="media/thumb12.jpg" alt="Woven Pattern"/></a> </div> </body> So here is the sample that works (for the list portion anyways), but seems excessive in terms of code since I'd have to repeat for each image: $(document).ready(function(){ $( "#list" ).click(function() { $( "a.l1" ).removeClass( "img" ); $( "a.l1" ).addClass( "lst" ); $( "a.l1" ).text( $( "a.l1" ).attr( "title" ); //repeat for l1 through l12 (that`s the letter L not a 1) }); $( "#grid" ).click(function() { $( "a.l1" ).removeClass( "lst" ); $( "a.l1" ).addClass( "grid" ); //actually have no idea at all how to get this back to the original img tag other than maybe .innerHTML??? //repeat for l1 through l12 (again, that`s the letter L not a 1) }); }): And here is kinda how I'd like it (Y'know, except in a way that works) $(document).ready(function(){ var i = 1; var selcur = $( "'a.l" + i + "'" ); var title = selcur.attr( "title" ); var image = '<img src="media/thumb' + i + '.jpg" alt="' + title + '"/>'; $( "#list" ).click(function() { while (1<=12) { selcur.addClass("lst"); selcur.removeClass("img"); selcur.text( title ); i++; } i = 1; }); $( "#grid" ).click(function() { while (1<=12) { selcur.removeClass("lst"); selcur.addClass("img"); selcur.text( image ); i++; } i = 1; }); }); Please tell me how I am going about this wrong, keep in mind again I'm new to this, I appreciate any and all responses! Is there a better way to do this? I really want to keep it simple.

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  • Is there a way to have customised text instead of subject in Thunderbird's inbox list?

    - by peterp
    I am getting a lot of informational emails like "You've got a new message from ..." or "Notification of Donation Received", which often do not contain any information in the subject so that I have to open the email to see who sent the message or who donated which amount. I'd love to be able to make TB parse incoming emails and then display something interesting instead of the original subject, e.g. by defining a regular expression pattern. I know how to write regular expressions, but I do not know whether there is a way or an addon to modify the displayed text in the messages view. EDIT for clarification: I would like donation notifications from Paypal not to be displayed as original Notification of Donation Received but rather Paypal: John Doe has donated 50$

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  • How to best propagate changes upwards a hierarchical structure for binding?

    - by H.B.
    If i have a folder-like structure that uses the composite design pattern and i bind the root folder to a TreeView. It would be quite useful if i can display certain properties that are being accumulated from the folder's contents. The question is, how do i best inform the folder that changes occurred in a child-element so that the accumulative properties get updated? The context in which i need this is a small RSS-FeedReader i am trying to make. This are the most important objects and aspects of my model: Composite interface: public interface IFeedComposite : INotifyPropertyChanged { string Title { get; set; } int UnreadFeedItemsCount { get; } ObservableCollection<FeedItem> FeedItems { get; } } FeedComposite (aka Folder) public class FeedComposite : BindableObject, IFeedComposite { private string title = ""; public string Title { get { return title; } set { title = value; NotifyPropertyChanged("Title"); } } private ObservableCollection<IFeedComposite> children = new ObservableCollection<IFeedComposite>(); public ObservableCollection<IFeedComposite> Children { get { return children; } set { children.Clear(); foreach (IFeedComposite item in value) { children.Add(item); } NotifyPropertyChanged("Children"); } } public FeedComposite() { } public FeedComposite(string title) { Title = title; } public ObservableCollection<FeedItem> FeedItems { get { ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); foreach (IFeedComposite child in Children) { foreach (FeedItem item in child.FeedItems) { feedItems.Add(item); } } return feedItems; } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } Feed: public class Feed : BindableObject, IFeedComposite { private string url = ""; public string Url { get { return url; } set { url = value; NotifyPropertyChanged("Url"); } } ... private ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); public ObservableCollection<FeedItem> FeedItems { get { return feedItems; } set { feedItems.Clear(); foreach (FeedItem item in value) { AddFeedItem(item); } NotifyPropertyChanged("Items"); } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } public Feed() { } public Feed(string url) { Url = url; } Ok, so here's the thing, if i bind a TextBlock.Text to the UnreadFeedItemsCount there won't be simple notifications when an item is marked unread, so one of my approaches has been to handle the PropertyChanged event of every FeedItem and if the IsUnread-Property is changed i have my Feed make a notification that the property UnreadFeedItemsCount has been changed. With this approach i also need to handle all PropertyChanged events of all Feeds and FeedComposites in Children of FeedComposite, from the sound of it, it should be obvious that this is not such a very good idea, you need to be very careful that items never get added or removed to any collection without having attached the PropertyChanged event handler first and things like that. Also: What do i do with the CollectionChanged-Events which necessarily also cause a change in the sum of the unread items count? Sounds like more event handling fun. It is such a mess, it would be great if anyone has an elegant solution to this since i don't want the feed-reader to end up as awful as my first attempt years ago when i didn't even know about DataBinding...

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  • logparser not matching on a LIKE pattern

    - by user79339
    Hi I seem to have the strangest problem. I am using logparser to search an event log for some text that I know is there (i copied and pasted the string from the event into the sql search string). But the sql LIKE statement is returning a empty results. But other LIKE statments seem to be working file. I have even tried using two '%' symbols in case the shell was trying to replace the search pattern with an environment variable '%%NavigationOccuredEventHandler%%', escaping the % with a \ and with a ' but all these just give me "No valid LIKE mask" error My logparser command - C:\Program Files\Log Parser 2.2LogParser.exe "select * from D:\Temp\07i132ppa1_app.evt where Message like '%NavigationOccuredEventHandler%' " -i:EVT -o:Datagrid The Entry in event log (found using "Select * from D:\Temp\07i132ppa1_app.evt" and doing a copy paste of relevant row) - 'D:\Temp\07i132ppa1_app.evt 5976788 2010-03-09 11:53:23 2010-03-09 11:53:23 2 1 Error event 0 None ICP Timestamp: 9/03/2010 1:53:23 AM Message: Error # 068464030040-07I132PPA1 System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.NullReferenceException: Object reference not set to an instance of an object. at ClientRegistration.Controller.ContactDetailsController.NavigationOccuredEventHandler(Object sender, NavigateEventArgs e) at Microsoft.ApplicationBlocks.UIProcess.UIPManager.NavigateEventHandler.Invoke(Object sender, NavigateEventArgs e) at Microsoft.ApplicationBlocks.UIProcess.UIPManager.InvokeEventHandlers(State state) in . . . Truncated for brevity ' output Statistics: Elements processed: 240993 Elements output: 0 Execution time: 59.47 seconds But if i searched for the pattern '%object reference not set%' it works fine, returns results. I copied and pasted the string into a dummy sql table and ran the sql query there and it works fine. Just doesn't seem to work in logparser. Very baffling. Any help would be much appreciated

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  • Using Unit of Work design pattern / NHibernate Sessions in an MVVM WPF

    - by Echiban
    I think I am stuck in the paralysis of analysis. Please help! I currently have a project that Uses NHibernate on SQLite Implements Repository and Unit of Work pattern: http://blogs.hibernatingrhinos.com/nhibernate/archive/2008/04/10/nhibernate-and-the-unit-of-work-pattern.aspx MVVM strategy in a WPF app Unit of Work implementation in my case supports one NHibernate session at a time. I thought at the time that this makes sense; it hides inner workings of NHibernate session from ViewModel. Now, according to Oren Eini (Ayende): http://msdn.microsoft.com/en-us/magazine/ee819139.aspx He convinces the audience that NHibernate sessions should be created / disposed when the view associated with the presenter / viewmodel is disposed. He presents issues why you don't want one session per windows app, nor do you want a session to be created / disposed per transaction. This unfortunately poses a problem because my UI can easily have 10+ view/viewmodels present in an app. He is presenting using a MVP strategy, but does his advice translate to MVVM? Does this mean that I should scrap the unit of work and have viewmodel create NHibernate sessions directly? Should a WPF app only have one working session at a time? If that is true, when should I create / dispose a NHibernate session? And I still haven't considered how NHibernate Stateless sessions fit into all this! My brain is going to explode. Please help!

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  • ASP MVC Ajax Controller pattern?

    - by Kevin Won
    My MVC app tends to have a lot of ajax calls (via JQuery.get()). It's sort of bugging me that my controller is littered with many tiny methods that get called via ajax. It seems to me to be sort of breaking the MVC pattern a bit--the controller is now being more of a data access component then a URI router. I refactored so that I have my 'true' controller for a page just performing standard routing responses (returing ActionResponse objects). So a call to /home/ will obviously kick up the HomeController class that will respond in the canonical controller fashion by returning a plain-jane View. I then moved my ajax stuff into a new controller class whose name I'm prefacing with 'Ajax'. So, for example, my page might have three different sections of functionality (say shopping cart or user account). I have an ajax controller for each of these (AjaxCartController, AjaxAccountController). There is really nothing different about moving the ajax call stuff into its own class--it's just to keep things cleaner. on client side obviously the JQuery would then use this new controller thusly: //jquery pseudocode call to specific controller that just handles ajax calls $.get('AjaxAccount/Details'.... (1) is there a better pattern in MVC for responding to ajax calls? (2) It seems to me that the MVC model is a bit leaky when it comes to ajax--it's not really 'controlling' stuff. It just happens to be the best and least painful way of handling ajax calls (or am I ignorant)? In other words, the 'Controller' abstraction doesn't seem to play nice with Ajax (at least from a patterns perspective). Is there something I'm missing?

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  • Regex pattern failing

    - by Scott Chamberlain
    I am trying a substring to find from the beginning of the string to the point that has the escape sequence "\r\n\r\n" my regex is Regex completeCall = new Regex(@"^.+?\r\n\r\n", RegexOptions.Compiled); it works great as long as you only have strings like 123\r\n\r\n however once you have the pattern 123\r\n 456\r\n\r\n the pattern no longer matches. Any advice on what I am doing wrong? Regex completeCall = new Regex(@"^.+?\r\n\r\n", RegexOptions.Compiled); Regex junkLine = new Regex(@"^\D", RegexOptions.Compiled); private void ClientThread() { StringBuilder stringBuffer = new StringBuilder(); (...) while(true) { (...) Match match = completeCall.Match(stringBuffer.ToString()); while (Match.Success) //once stringBuffer has somthing like "123\r\n 456\r\n\r\n" Match.Success always returns false. { if (junkLine.IsMatch(match.Value)) { (...) } else { (...) } stringBuffer.Remove(0, match.Length); // remove the processed string match = completeCall.Match(stringBuffer.ToString()); // check to see if more than 1 call happened while the thread was sleeping. } Thread.Sleep(1000); }

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  • Best pattern for storing (product) attributes in SQL Server

    - by EdH
    We are starting a new project where we need to store product and many product attributes in a database. The technology stack is MS SQL 2008 and Entity Framework 4.0 / LINQ for data access. The products (and Products Table) are pretty straightforward (a SKU, manufacturer, price, etc..). However there are also many attributes to store with each product (think industrial widgets). These may range from color to certification(s) to pipe size. Every product may have different attributes, and some may have multiples of the same attribute (Ex: Certifications). The current proposal is that we will basically have a name/value pair table with a FK back to the product ID in each row. An example of the attributes Table may look like this: ProdID AttributeName AttributeValue 123 Color Blue 123 FittingSize 1.25 123 Certification AS1111 123 Certification EE2212 123 Certification FM.3 456 Pipe 11 678 Color Red 999 Certification AE1111 ... Note: Attribute name would likely come from a lookup table or enum. So the main question here is: Is this the best pattern for doing something like this? How will the performance be? Queries will be based on a JOIN of the product and attributes table, and generally need many WHEREs to filter on specific attributes - the most common search will be to find a product based on a set of known/desired attributes. If anyone has any suggestions or a better pattern for this type of data, please let me know. Thanks! -Ed

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  • Flexible Decorator Pattern?

    - by Omar Kooheji
    I was looking for a pattern to model something I'm thinking of doing in a personal project and I was wondering if a modified version of the decorator patter would work. Basicly I'm thinking of creating a game where the characters attributes are modified by what items they have equiped. The way that the decorator stacks it's modifications is perfect for this, however I've never seen a decorator that allows you to drop intermediate decorators, which is what would happen when items are unequiped. Does anyone have experience using the decorator pattern in this way? Or am I barking up the wrong tree? Clarification To explain "Intermediate decorators" if for example my base class is coffe which is decorated with milk which is decorated with sugar (using the example in Head first design patterns) milk would be an intermediate decorator as it decorates the base coffee, and is decorated by the sugar. Yet More Clarification :) The idea is that items change stats, I'd agree that I am shoehorning the decorator into this. I'll look into the state bag. essentially I want a single point of call for the statistics and for them to go up/down when items are equiped/unequiped. I could just apply the modifiers to the characters stats on equiping and roll them back when unequiping. Or whenever a stat is asked for iterate through all the items and calculate the stat. I'm just looking for feedback here, I'm aware that I might be using a chainsaw where scissors would be more appropriate...

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  • Best Pattern for AllowUnsafeUpdates

    - by webwires
    So far, in my research I have seen that it is unwise to set AllowUnsafeUpdates on GET request operation to avoid cross site scripting. But, if it is required to allow this, what is the proper way to handle the situation to mitigate any exposure? Here is my best first guess on a reliable pattern if you absolutely need to allow web or site updates on a GET request. Best Practice? protected override void OnLoad(System.EventArgs e) { if(Request.HttpMethod == "POST") { SPUtility.ValidateFormDigest(); // will automatically set AllowSafeUpdates to true } // If not a POST then AllowUnsafeUpdates should be used only // at the point of update and reset immediately after finished // NOTE: Is this true? How is cross-site scripting used on GET // and what mitigates the vulnerability? } // Point of item update SPSecurity.RunWithElevatedPrivledges(delegate() { using(SPSite site = new SPSite(SPContext.Current.Site.Url)) { using (SPWeb web = site.RootWeb) { bool allowUpdates = web.AllowUnsafeUpdates; //store original value web.AllowUnsafeUpdates = true; //... Do something and call Update() ... web.AllowUnsafeUpdates = allowUpdates; //restore original value } } }); Feedback on the best pattern is appreciated.

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  • Design pattern to use instead of multiple inheritance

    - by mizipzor
    Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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  • 3 tier application pattern suggestion

    - by Maxim Gershkovich
    I have attempted to make my first 3 tier application. In the process I have run into one problem I am yet to find an optimal solution for. Basically all my objects use an IFillable interface which forces the implementation of a sub as follows Public Sub Fill(ByVal Datareader As Data.IDataReader) Implements IFillable.Fill This sub then expects the Ids from the datareader will be identical to the properties of the object as such. Me.m_StockID = Datareader.GetGuid(Datareader.GetOrdinal("StockID")) In the end I end up with a datalayer that looks something like this. Public Shared Function GetStockByID(ByVal ConnectionString As String, ByVal StockID As Guid) As Stock Dim res As New Stock Using sqlConn As New SqlConnection(ConnectionString) sqlConn.Open() res.Fill(StockDataLayer.GetStockByIDQuery(sqlConn, StockID)) End Using Return res End Function Mostly this pattern seems to make sense. However my problem is, lets say I want to implement a property for Stock called StockBarcodeList. Under the above mentioned pattern any way I implement this property I will need to pass a connectionstring to it which obviously breaks my attempt at layer separation. Does anyone have any suggestions on how I might be able to solve this problem or am I going about this the completely wrong way? Does anyone have any suggestions on how I might improve my implementation? Please note however I am deliberately trying to avoid using the dataset in any form.

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  • Strategy Pattern with Type Reflection affecting Performances ?

    - by Aurélien Ribon
    Hello ! I am building graphs. A graph consists of nodes linked each other with links (indeed my dear). In order to assign a given behavior to each node, I implemented the strategy pattern. class Node { public BaseNodeBehavior Behavior {get; set;} } As a result, in many parts of the application, I am extensively using type reflection to know which behavior a node is. if (node.Behavior is NodeDataOutputBehavior) workOnOutputNode(node) .... My graph can get thousands of nodes. Is type reflection greatly affecting performances ? Should I use something else than the strategy pattern ? I'm using strategy because I need behavior inheritance. For example, basically, a behavior can be Data or Operator, a Data behavior can IO, Const or Intermediate and finally an IO behavior can be Input or Output. So if I use an enumeration, I wont be able to test for a node behavior to be of data kind, I will need to test it to be [Input, Output, Const or Intermediate]. And if later I want to add another behavior of Data kind, I'm screwed, every data-testing method will need to be changed.

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  • Singleton Pattern combine with a Decorator

    - by Mike
    Attached is a classic Decorator pattern. My question is how would you modify the below code so that you can wrap zero or one of each topping on to the Pizza Right now I can have a Pepporini - Sausage -- Pepporini -- Pizza class driving the total cost up to $10, charging twice for Pepporini. I don't think I want to use the Chain of Responsibility pattern as order does not matter and not all toppings are used? Thank you namespace PizzaDecorator { public interface IPizza { double CalculateCost(); } public class Pizza: IPizza { public Pizza() { } public double CalculateCost() { return 8.00; } } public abstract class Topping : IPizza { protected IPizza _pizzaItem; public Topping(IPizza pizzaItem) { this._pizzaItem = pizzaItem; } public abstract double CalculateCost(); } public class Pepporini : Topping { public Pepporini(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 0.50; } } public class Sausage : Topping { public Sausage(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 1.00; } } public class Onions : Topping { public Onions(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + .25; } } }

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  • (nested) user controls within a mvp pattern causing sporadic problems

    - by LLEA
    hi everyone, I have a serious problem with nested user controls (UCs) in WinForms while trying to implement the mvp pattern (passive view). The project consists of one model (designed as a singleton) and a set of different presenters with corresponding view interfaces. To avoid one huge view interface and therefore an overloaded main UI, I decided to make use of a set of different UCs. Each UC has one view interface and one presenter that can access the model. But there are nested UCs: meaning that one specialised UC implements sort of a basic UC. The main UI just represents a container for all those UCs. So far, so good (if not, please ask)?! There are two problems that I am facing now (but I guess both are of the same origin): From time to time it is not possible anymore to load the UCs and test them within the Visual Studio 2008 User Control Test Container. The error message just says that a project with an output type of class library cannot be started directly etc. I can "handle" that by unloading all UC projects and reloading them afterwards. (I guess the references to all mvp components and other UCs are then updated). Assuming that the implementation of my mvp pattern is okay and all those UCs are testable within the VS Test Container at a certain time - there is the biggest problem still left: I am not able to add any UC (even the basic and unnested ones) to a simple Form (UI). The error message: error message.jpg Could it be that my basic UC causes all these Problems?! It consists of two simple ComboBoxes and implements a basic presenter and basic view interface. Whenever I add this UC to a different UC the VS designer adds two references to the public getter methods of the UC as resources. I then manually remove those resources from the resx-file and commend the corresponding lines in the designer file. thx in advance

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  • What is the right pattern for a async data fetching method in .net async/await

    - by s093294
    Given a class with a method GetData. A few other clients call GetData, and instead of it fetching data each time, i would like to create a pattern where the first call starts the task to get the data, and the rest of the calls wait for the task to complete. private Task<string> _data; private async Task<string> _getdata() { return "my random data from the net"; //get_data_from_net() } public string GetData() { if(_data==null) _data=_getdata(); _data.wait(); //are there not a problem here. cant wait a task that is already completed ? if(_data.status != rantocompletion) _data.wait() is not any better, it might complete between the check and the _data.wait? return _data.Result; } How would i do the pattern correctly? (Solution) private static object _servertime_lock = new object(); private static Task<string> _servertime; private static async Task<string> servertime() { try { var thetvdb = new HttpClient(); thetvdb.Timeout = TimeSpan.FromSeconds(5); // var st = await thetvdb.GetStreamAsync("http://www.thetvdb.com/api/Updates.php?type=none"); var response = await thetvdb.GetAsync("http://www.thetvdb.com/api/Updates.php?type=none"); response.EnsureSuccessStatusCode(); Stream stream = await response.Content.ReadAsStreamAsync(); XDocument xdoc = XDocument.Load(stream); return xdoc.Descendants("Time").First().Value; } catch { return null; } } public static async Task<string> GetServerTime() { lock (_servertime_lock) { if (_servertime == null) _servertime = servertime(); } var time = await _servertime; if (time == null) _servertime = null; return time; }

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  • Is this a good decorator pattern for javascript?

    - by Kucebe
    I need some simple objects that could become more complex later, with many different properties, so i thought to decorator pattern. I made this looking at Crockford's power constructor and object augmentation: //add property to object Object.prototype.addProperty = function(name, func){ for(propertyName in this){ if(propertyName == name){ throw new Error(propertyName + " is already defined"); } } this[name] = func; }; //constructor of base object var BaseConstructor = function(param){ var _privateVar = param; return{ getPrivateVar: function(){ return _privateVar; } }; }; //a simple decorator, adds one private attribute and one privileged method var simpleDecorator = function(obj, param){ var _privateVar = param; var privilegedMethod1 = function(){ return "privateVar of decorator is: " + _privateVar; }; obj.addProperty("privilegedMethod1", privilegedMethod1); return obj; } //a more complex decorator, adds public and private properties var complexDecorator = function(obj, param1, param2){ //private properties var _privateVar = param1; var _privateMethod = function(x){ for(var i=0; i<x; i++){ _privateVar += x; } return _privateVar; }; //public properties var publicVar = "I'm public"; obj.addProperty("publicVar", publicVar); var privilegedMethod2 = function(){ return _privateMethod(param2); }; obj.addProperty("privilegedMethod2", privilegedMethod2); var publicMethod = function(){ var temp = this.privilegedMethod2(); return "do something: " + temp + " - publicVar is: " + this.publicVar; }; obj.addProperty("publicMethod", publicMethod); return obj; } //new basic object var myObj = BaseConstructor("obj1"); //the basic object will be decorated var myObj = simpleDecorator(obj, "aParam"); //the basic object will be decorated with other properties var myObj = complexDecorator(obj, 2, 3); Is this a good way to have Decorator Pattern in javascript? Are there other better ways to do this?

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  • PHP OOP: Avoid Singleton/Static Methods in Domain Model Pattern

    - by sunwukung
    I understand the importance of Dependency Injection and its role in Unit testing, which is why the following issue is giving me pause: One area where I struggle not to use the Singleton is the Identity Map/Unit of Work pattern (Which keeps tabs on Domain Object state). //Not actual code, but it should demonstrate the point class Monitor{//singleton construction omitted for brevity static $members = array();//keeps record of all objects static $dirty = array();//keeps record of all modified objects static $clean = array();//keeps record of all clean objects } class Mapper{//queries database, maps values to object fields public function find($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; } $values = $this->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); Monitor::new[$id]=$Object return $Object; } $User = $UserMapper->find(1);//domain object is registered in Id Map $User->changePropertyX();//object is marked "dirty" in UoW // at this point, I can save by passing the Domain Object back to the Mapper $UserMapper->save($User);//object is marked clean in UoW //but a nicer API would be something like this $User->save(); //but if I want to do this - it has to make a call to the mapper/db somehow $User->getBlogPosts(); //or else have to generate specific collection/object graphing methods in the mapper $UserPosts = $UserMapper->getBlogPosts(); $User->setPosts($UserPosts); Any advice on how you might handle this situation? I would be loathe to pass/generate instances of the mapper/database access into the Domain Object itself to satisfy DI - At the same time, avoiding that results in lots of calls within the Domain Object to external static methods. Although I guess if I want "save" to be part of its behaviour then a facility to do so is required in its construction. Perhaps it's a problem with responsibility, the Domain Object shouldn't be burdened with saving. It's just quite a neat feature from the Active Record pattern - it would be nice to implement it in some way.

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  • Abstract factory pattern on top of IoC?

    - by Sergei
    I have decided to use IoC principles on a bigger project. However, i would like to get something straight that's been bothering me for a long time. The conclusion that i have come up with is that an IoC container is an architectural pattern, not a design pattern. In other words, no class should be aware of its presence and the container itself should be used at the application layer to stitch up all components. Essentially, it becomes an option, on top of a well designed object-oriented model. Having said that, how is it possible to access resolved types without sprinkling IoC containers all over the place (regardless of whether they are abstracted or not)? The only option i see here is to utilize abstract factories which use an IoC container to resolve concrete types. This should be easy enough to swap out for a set of standard factories. Is this a good approach? Has anyone on here used it and how well did it work for you? Is there anything else available? Thanks!

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