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  • Database Replication OOD Pattern

    - by MrOnigiri
    Greetings fellow overflowers, After reading on MSDN about correct strategies on how to perform database replication, and understanding their suggestion on Master-Subordinate Incremental Replication. It left me wondering, what OOD design pattern should I use on this... The main elements of this strategy are the Acquirer, the Manipulator and the Writer. The first fetches data from the database and passes on to the second which might perform simple transformations to the data, before handling it to the final element, the writer, that writes the desired data on the destination Database. I thought about using the Chain of Responsibility pattern, but the Acquirer, Manipulator and Writer don't share a common role among theme, so It makes no sense. Should these elements be written as separate classes, or methods inside my service? Of course I'll be creating a DB Helper class as well, but that doesn't constitutes a problem. Wondering what your opinions on this are! Thanks for your replies

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  • WPF MVVM Pattern - References

    - by KroaX
    Hi everyone I wanted to know if some of you guys can post some articles, blog posts etc. that explain the MVVM Pattern in detail. There are not much explainations out there I think ( except Tutorials). I'm going to write my exam about WPF and also want to build in the MVVM Pattern. So I need some good references that are also digging a little deeper. I think I already have read a lot of texts about MVVM, but maybe you guys got some I didn't read yet. Would really appreciate if you would share your links to good and worth reading articles and explanations

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  • quantity of measurable units design pattern

    - by Berryl
    Hello I am thinking through a nice pattern to be useful across domains of measurable units (ie, Length, Time) and came up with the following use case and initial classes, and of course, questions! 1) Does a Composite pattern help or complicate? 2) Should the Convert method(s) in the ComposityNode be a separate converter class? All comments appreciated. Cheers, Berryl Example Use Case: var inch = new ConvertableUnit("inch", 1) var foot = new ConvertableUnit("foot", 12) var imperialUnits = new CompositeConvertableUnit("imperial units", .024) imperialUnits.AddChild(inch) imperialUnits.AddChild(foot) var meter = new ConvertableUnit("meter", 1) var millimeter = new ConvertableUnit("millimeter ", .001) var imperialUnits = new CompositeConvertableUnit("metric units", 1) imperialUnits.AddChild(meter) imperialUnits.AddChild(millimeter) var oneInch = new Quantity(1, inch); var oneFoot = new Quantity(1, foot); oneFoot.ToBase() // "12 inches" var oneMeter = new Quantity(1, meter); oneInch.ToBase() // .024 meters Possible Solution ConvertableUnit : Node double Rate string Name Quantity ConvertableUnit Unit double Amount CompositeConvertableUnit : Node ISet<ConvertableUnit> _children ConvertableUnit BaseUnit {get{ return _children.Where(c=>c.Rate == 1).First() } } Quantity ConvertTo(Quantity from, Quantity to) Quantity ToBase(Quantity from);

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  • What is the "Dispatcher" design pattern?

    - by Ben Farmer
    What is the "dispatcher" pattern and how would I implement it in code? I have a property bag of generic objects and would like to have the retrieval delegated to a generic method. Currently, I have properties looking for a specific key in the bag. For example: private Dictionary<String, Object> Foo { get; set; } private const String WidgetKey = "WIDGETKEY"; public Widget? WidgetItem { get { return Foo.ContainsKey(WidgetKey) ? Foo[WidgetKey] as Widget: null; } set { if (Foo.ContainsKey(WidgetKey)) Foo[WidgetKey] = value; else Foo.Add(WidgetKey, value); } } It was suggested that this could be more generic with the "dispatcher" pattern, but I've been unable to find a good description or example. I'm looking for a more generic way to handle the property bag store/retrieve.

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  • how to implement unitofwork pattern when using subsonic 2.1(Repository pattern) ?

    - by ROHITH
    I am using subsonic repository pattern(2.1) for asp.net mvc application.In my application,there are many repositories like categoryRepository,Blogrepository etc.Inside each of this repository i am calling subsonic's DB.Select().From()...ExecuteReader() and then loading domain objects from those reader. In the controller action i make multiple calls from these repositories for e.g. List<IBlog> blogs=_blogRepository.GetHottestBlogs(); List<ICategory> categories=_categoryRepository.GetAll(); do i have to implement any unitofwork pattern for this ?.My doubt is that how subsonic performs each operation DB.Update/Insert/Select .Is a TransactionScope is enough for batch update or do i have to use SharedDbConnectionScope to get better performance?

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  • Suggestions: Anti-Pattern counter-examples

    - by Tom W
    It doesn't seem that this exact question has been asked before, so I'll fire away: Most of us are familiar with the concept of an anti-pattern. However, avoiding implementation of anti-patterns can in principle swing too far the other way and cause problems itself. As an example, "Design by Committee" has a counter-example that I'd call "Design by Maverick" - wherein the design of an important feature is handed off to an individual to do what they think best, with the intention of reviewing their work later and deciding whether it should be finalised or go through another iteration. This takes much longer in practice as the rest of the team are occupied by other things, and can end up with a feature that's useful to nobody, particularly if the Maverick is not themselves an experienced end-user. Does anyone have any more examples of anti-pattern counter-examples?

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  • DAO design pattern and using it across multiple tables

    - by Casey
    I'm looking for feedback on the Data Access Object design pattern and using it when you have to access data across multiple tables. It seems like that pattern, which has a DAO for each table along with a Data Transfer Object (DTO) that represents a single row, isn't too useful for when dealing with data from multiple tables. I was thinking about creating a composite DAO and corresponding DTO that would return the result of, let's say performing a join on two tables. This way I can use SQL to grab all the data instead of first grabbing data from one using one DAO and than the second table using the second DAO, and than composing them together in Java. Is there a better solution? And no, I'm not able to move to Hibernate or another ORM tool at the moment. Just straight JDBC for this project.

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  • how can i use switch statement on type-safe enum pattern

    - by Fer
    I found a goodlooking example about implementation enums in a different way. That is called type-safe enum pattern i think. I started using it but i realized that i can not use it in a switch statement. My implementation looks like the following: public sealed class MyState { private readonly string m_Name; private readonly int m_Value; public static readonly MyState PASSED= new MyState(1, "OK"); public static readonly MyState FAILED= new MyState(2, "ERROR"); private MyState(int value, string name) { m_Name = name; m_Value = value; } public override string ToString() { return m_Name; } public int GetIntValue() { return m_Value; } } What can i add to my class in order to be able to use this pattern in switch statements in C#? Thanks.

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  • Please help clarify my regex pattern

    - by Dmitriy Sosunov
    I have the following string: <script>m('02:29:1467301/>Sender1*>some text message?<<02:29:13625N1/>Sender2*>Recipient2: another message??<>A<<02:29:1393100=>User1*|0User2*|%></B><<','');</script> N.B. messages are separated by << I need extract from message the following parts: 1. Time 2. Sender 3. Recipient 4. Text Recipient may being defined or not, this field is optional. I do this by the following pattern: (?<message>(?<time>\d{1,2}:\d{1,2}:[0-9a-z]+)/>(?<messageData>(?<sender>.+?)\*>(.+?)))<< But, I cannot extract recipient separately from the message text. (?<message>(?<time>\d{1,2}:\d{1,2}:[0-9a-z]+)/>(?<messageData>(?<sender>.+?)\*>(((?<recipient>.+?):){0,1}(?<messageText>.+?))))<< Please help correct my pattern.

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  • Android pattern for activity "flows"

    - by Otto
    I'm developing an android app that has a bunch of screens (activities) that are supposed to have "continue" and "back" buttons at the top. Can you tell me the right pattern for implementing this? I've seen some iPhone apps that have this but Android apps usually don't (I think partly because the back button is part of the phone). I found a post online about an Activity class that has "sub activities" which kind of seems like what I want to do, but I'm wondering if there's a simpler solution or pattern for creating flows like this (in which several activities are linked with continue/back buttons).

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  • ready to use design pattern APIs for PHP?

    - by ajsie
    i know that in Java you can use their built-in APIs for design pattern. eg. if you want to use the observer pattern, you just have to extend your Subject class with the Observable class. is this possible for PHP? are there any libraries for the design patterns ready to use. in this way you don't have to reinvent the wheel and you also let many developers follow a standard. does Zend library have these API:s?

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  • Beginner Design pattern question (Web Services involved)

    - by zombie
    Hi all ! I am a noob to web services world. I need to develop a login validator module and expose it as a service. I want it to be service independent, i.e I should have the option of exposing it as a SOAP service or REST service in the future. What pattern should I follow ? Sorry if I am unclear in my requirements, I can clarify as per need. Thanks !! Edit : I am using Eclipse as an IDE and Jersey libraries. I am not into any framework, simply using the MVC pattern. I find a lot of difference between SOAP ann REST methods, so I want my methods to be implementation independent - i.e I should be easily able to use my method through a SOAP or REST service call as per need. What should I do for maximum flexibility ?

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  • Using scope, defined in parent model, inside it's child (STI pattern)

    - by Anton
    I implement a class hierarchy using STI pattern class A scope :aaa, where([someField]:[someValue]) end class B < A end The problem is that when I try to call something like: B.limit(5).aaa => SELECT "[table]".* FROM "[table]" WHERE "[table]"."type" IN ('A') AND ([someField] = [someValue]) LIMIT 5 So I am getting 5 objects of type A, which satisfies scope :aaa But I need to do the same with rows where type = "B" Is there any way to use scopes from parent, without redifinning it in childs in STI pattern? Thanks in advance EDITED I just discussed it with my frind and he showed me one important thing. A in not the root class of STI. IN fact whole hierarchy looks like class O < ActiveRecord::Base end class A < O scope ..... ..... end class B < A end maybe the reason is in hierarchy itself?...

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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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  • What's a good place to unregister an observer from the notification center?

    - by mystify
    When I add an observer to the default notification center, where would I unregister that? Example: I have a UIView subclass which lives inside a view controller. That subclass is an observer for the FooBarNotification. If this notification is posted, that view will get it. But now, the view controller decides to throw away the view. Is the best place the -dealloc method of the view itself? Are there any rules like memory management rules? For example: Must I unregister an observer where I registered it? i.e. the view registers itself in it's init method, so it should unregister itself in it's -dealloc method? (not talking about push notifications, but NSNotificationCenter)

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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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