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  • Implementing the procducer-consumer pattern with .NET 4.0

    - by bitbonk
    With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing/enqueuing task items and another thread executes/dequeues these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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  • Explain "Leader/Follower" Pattern

    - by Alex B
    I can't seem to find a good explanation of "Leader/Follower" pattern. All explanations either simply refer to it in the context of some problem, or are completely meaningless. Can anyone explain to the the mechanics of how this pattern works, and why and how it improves performance over more traditional asynchronous IO models? Examples and links to diagrams are appreciated too.

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  • Doubleton Pattern Implementation

    - by Pierreten
    I'm leveraging the Doubleton Pattern from this link http://www.codeproject.com/KB/architecture/designpattern_doubleton.aspx in my own code. I think it makes things a lot easier since the Singleton only provides one instance, but I get two with this pattern. I was wondering if it would make sense to have it implement an interface so I can inject it into my domain layer.

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  • My User control belonging to which Design Pattern??

    - by prashant
    Hello, I am creating a reusable component in C#.net. For that i have started a Control Library project and added a Control. Class MyControl : Control{} My user control just displays some images which will be used in many Windows Applications. Can you please tell me which design pattern i am using here. I am unable to decide which pattern they belongs. Thanks

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  • How to dispose the objects created by factory pattern

    - by Ram
    Hi, I am using Factory pattern to create .NET objects of a class. I also need to make sure that all such objects should be disposed before application terminates. Where and How can I dispose the objects created by factory pattern? Shall I dispose in the class in which I am getting the objects created by factory?

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  • Is there a pattern or best practice for passing a reference type to multiple classes vs a static class?

    - by Dave
    My .NET application creates HTML files, and as such, the structure looks like variable myData BuildHomePage() variable graph = new BuildGraphPage(myData) variable table = BuildTablePage(myData) BuildGraphPage and BuildTablePage both require access data, the myData object. In the above example, I've passed the myData object to 2 constructors. This is what I'm doing now, in my current project. The myData object, and it's properties are all readonly. The problem is, the number of pages which will require this object has grown. In the real project, there are currently 4, but the new spec is to have about 20. Passing this object to the constructor of each new object and assigning it to a field is a little time consuming, but not a hardship! This poses the question whether it's better practice to continue as I have, or to refactor and create a new static class for myData which can be referenced from any where in my project. I guess my abilities to use Google are poor, because I did try and find an appropriate pattern as I am sure this type of design must be common place but my results returned nothing. Is there a pattern which is suited, or do best practices lean towards one implementation over another.

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  • Are first-class functions a substitute for the Strategy pattern?

    - by Prog
    The Strategy design pattern is often regarded as a substitute for first-class functions in languages that lack them. So for example say you wanted to pass functionality into an object. In Java you'd have to pass in the object another object which encapsulates the desired behavior. In a language such as Ruby, you'd just pass the functionality itself in the form of an annonymous function. However I was thinking about it and decided that maybe Strategy offers more than a plain annonymous function does. This is because an object can hold state that exists independently of the period when it's method runs. However an annonymous function by itself can only hold state that ceases to exist the moment the function finishes execution. So my question is: when using a language that features first-class functions, would you ever use the Strategy pattern (i.e. encapsulate the functionality you want to pass around in an explicit object), or would you always use an annonymous function? When would you decide to use Strategy when you can use a first-class function?

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  • Is there a name for the Builder Pattern where the Builder is implemented via interfaces so certain parameters are required?

    - by Zipper
    So we implemented the builder pattern for most of our domain to help in understandability of what actually being passed to a constructor, and for the normal advantages that a builder gives. The one twist was that we exposed the builder through interfaces so we could chain required functions and unrequired functions to make sure that the correct parameters were passed. I was curious if there was an existing pattern like this. Example below: public class Foo { private int someThing; private int someThing2; private DateTime someThing3; private Foo(Builder builder) { this.someThing = builder.someThing; this.someThing2 = builder.someThing2; this.someThing3 = builder.someThing3; } public static RequiredSomething getBuilder() { return new Builder(); } public interface RequiredSomething { public RequiredDateTime withSomething (int value); } public interface RequiredDateTime { public OptionalParamters withDateTime (DateTime value); } public interface OptionalParamters { public OptionalParamters withSeomthing2 (int value); public Foo Build ();} public static class Builder implements RequiredSomething, RequiredDateTime, OptionalParamters { private int someThing; private int someThing2; private DateTime someThing3; public RequiredDateTime withSomething (int value) {someThing = value; return this;} public OptionalParamters withDateTime (int value) {someThing = value; return this;} public OptionalParamters withSeomthing2 (int value) {someThing = value; return this;} public Foo build(){return new Foo(this);} } } Example of how it's called: Foo foo = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).build(); Foo foo2 = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).withSomething2(3).build();

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  • Java Matcher groups: Understanding The difference between "(?:X|Y)" and "(?:X)|(?:Y)"

    - by user358795
    Can anyone explain: Why the two patterns used below give different results? (answered below) Why the 2nd example gives a group count of 1 but says the start and end of group 1 is -1? public void testGroups() throws Exception { String TEST_STRING = "After Yes is group 1 End"; { Pattern p; Matcher m; String pattern="(?:Yes|No)(.*)End"; p=Pattern.compile(pattern); m=p.matcher(TEST_STRING); boolean f=m.find(); int count=m.groupCount(); int start=m.start(1); int end=m.end(1); System.out.println("Pattern=" + pattern + "\t Found=" + f + " Group count=" + count + " Start of group 1=" + start + " End of group 1=" + end ); } { Pattern p; Matcher m; String pattern="(?:Yes)|(?:No)(.*)End"; p=Pattern.compile(pattern); m=p.matcher(TEST_STRING); boolean f=m.find(); int count=m.groupCount(); int start=m.start(1); int end=m.end(1); System.out.println("Pattern=" + pattern + "\t Found=" + f + " Group count=" + count + " Start of group 1=" + start + " End of group 1=" + end ); } } Which gives the following output: Pattern=(?:Yes|No)(.*)End Found=true Group count=1 Start of group 1=9 End of group 1=21 Pattern=(?:Yes)|(?:No)(.*)End Found=true Group count=1 Start of group 1=-1 End of group 1=-1

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  • Winforms Which Design Pattern / Agile Methodology to choose

    - by ZedBee
    I have developed desktop (winforms) applications without following any proper design pattern or agile methodologies. Now I have been given the task to re-write an existing ERP application in C# (Winforms). I have been reading about Domain Driven Design, scrum, extreme programming, layered architecture etc. Its quite confusing and really hard (because of time limitations) to go and try each and every method and then deciding which way to go. Its very hard for me to understand the bigger picture and see which pattern and agile methodology to follow. To be more specific about what I want to know is that: Is it possible to follow Domain Driven Design and still be agile. Should I choose Extreme programming or scrum in this specific scenario Where does MVP and MVVM fits, which one would be a better option for me

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  • Adding line with text between pattern and next occurence of the same pattern in bash

    - by kasper
    I am writing a bash script that modifies a file that looks like this: --- usr1 --- data data data data data data data data data data data data --- usr2 --- data data data data data data data data --- usr3 --- data data data data --- endline --- One question is: How to add next user line --- usrn --- after last user data lines? Second one is: How to delete specific user data lines (data lines and --- userx ---) i.e. I would like to delete usr2 with all his data set. It must work on bash 2.05 :) and I think it will use awk or sed, but I'm not sure.

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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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  • Design pattern for mouse interaction

    - by mike
    I need some opinions on what is the "ideal" design pattern for a general mouse interaction. Here the simplified problem. I have a small 3d program (QT and openGL) and I use the mouse for interaction. Every interaction is normally not only a single function call, it is mostly performed by up to 3 function calls (initiate, perform, finalize). For example, camera rotation: here the initial function call will deliver the current first mouse position, whereas the performing function calls will update the camera etc. However, for only a couple of interactions, hardcoding these (inside MousePressEvent, MouseReleaseEvent MouseMoveEvent or MouseWheelEvent etc) is not a big deal, but if I think about a more advanced program (e.g 20 or more interactions) then a proper design is needed. Therefore, how would you design such a interactions inside QT. I hope I made my problem clear enough, otherwise don't bother complain :-) Thanks

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  • Specification Pattern and Boolean Operator Precedence

    - by Anders Nielsen
    In our project, we have implemented the Specification Pattern with boolean operators (see DDD p 274), like so: public abstract class Rule { public Rule and(Rule rule) { return new AndRule(this, rule); } public Rule or(Rule rule) { return new OrRule(this, rule); } public Rule not() { return new NotRule(this); } public abstract boolean isSatisfied(T obj); } class AndRule extends Rule { private Rule one; private Rule two; AndRule(Rule one, Rule two) { this.one = one; this.two = two; } public boolean isSatisfied(T obj) { return one.isSatisfied(obj) && two.isSatisfied(obj); } } class OrRule extends Rule { private Rule one; private Rule two; OrRule(Rule one, Rule two) { this.one = one; this.two = two; } public boolean isSatisfied(T obj) { return one.isSatisfied(obj) || two.isSatisfied(obj); } } class NotRule extends Rule { private Rule rule; NotRule(Rule obj) { this.rule = obj; } public boolean isSatisfied(T obj) { return !rule.isSatisfied(obj); } } Which permits a nice expressiveness of the rules using method-chaining, but it doesn't support the standard operator precedence rules of which can lead to subtle errors. The following rules are not equivalent: Rule<Car> isNiceCar = isRed.and(isConvertible).or(isFerrari); Rule<Car> isNiceCar2 = isFerrari.or(isRed).and(isConvertible); The rule isNiceCar2 is not satisfied if the car is not a convertible, which can be confusing since if they were booleans isRed && isConvertible || isFerrari would be equivalent to isFerrari || isRed && isConvertible I realize that they would be equivalent if we rewrote isNiceCar2 to be isFerrari.or(isRed.and(isConvertible)), but both are syntactically correct. The best solution we can come up with, is to outlaw the method-chaining, and use constructors instead: OR(isFerrari, AND(isConvertible, isRed)) Does anyone have a better suggestion?

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  • nhibernate fluent repository pattern insert problem

    - by voam
    I am trying to use Fluent NHibernate and the repository pattern. I would like my business layer to not be knowledgeable of the data persistence layer. Ideally I would pass in an initialized domain object to the insert method of the repository and all would be well. Where I run into problems is if the object being passed in has a child object. For example say I want to insert an a new order for a customer, and the customer is a property of the order object. I would like to do something like this: Customer c = new Customer; c.CustomerId = 1; Order o = new Order; o.Customer = c; repository.InsertOrder(o); The problem is that using NHiberate the CustomerId field is only privately settable so I can not set it directly like this. so what I have ended up doing is have my repository have an interface of Order InsertOrder(int customerId) where all the foreign keys get passed in as parameters. Somehow this just doesn't seem right. The other approach was to use the NHibernate session variable to load a customer object in my business model and then have the order passed in to the repository but this defeats my persistence ignorance ideal. Should I throw this persistence ignorance out the window or am I missing something here? Thanks

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  • Accessing jQuery objects in the module pattern

    - by Stewart
    Hello, Really getting in to javascript and looking around at some patterns. One I have come accross is the module pattern. Its seems like a nice way to think of chucks of functionality so I went ahead and tried to implement it with jQuery. I ran in to a snag though. Consider the following code <!DOCTYPE html> <html> <head> <meta http-equiv="Content-type" content="text/html; charset=utf-8"> <title>index</title> <script type="text/javascript" charset="utf-8" src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script> <script type="text/javascript" charset="utf-8"> $(document).ready(function(){ var TestClass2 = (function(){ var someDiv; return { thisTest: function () { someDiv = document.createElement("div"); $(someDiv).append("#index"); $(someDiv).html("hello"); $(someDiv).addClass("test_class"); } } })(); TestClass2.thisTest(); }); </script> </head> <body id="index" onload=""> <div id="name"> this is content </div> </body> </html> The above code alerts the html content of the div and then adds a class. These both use jQuery methods. The problem is that the .html() method works fine however i can not add the class. No errors result and the class does not get added. What is happening here? Why is the class not getting added to the div?

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  • Observer Design Pattern - multiple event types

    - by David
    I'm currently implementing the Observer design pattern and using it to handle adding items to the session, create error logs and write messages out to the user giving feedback on their actions (e.g. You've just logged out!). I began with a single method on the subject called addEvent() but as I added more Observers I found that the parameters required to detail all the information I needed for each listener began to grow. I now have 3 methods called addMessage(), addStorage() and addLog(). These add data into an events array that has a key related to the event type (e.g. log, message, storage) but I'm starting to feel that now the subject needs to know too much about the listeners that are attached. My alternative thought is to go back to addEvent() and pass an event type (e.g. USER_LOGOUT) along with the data associated and each Observer maintains it's own list of event handles it is looking for (possibly in a switch statement), but this feels cumbersome. Also, I'd need to check that sufficient data had also been passed along with the event type. What is the correct way of doing this? Please let me know if I can explain any parts of this further. I hope you can help and see the problem I'm battling with.

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  • f# pattern matching with types

    - by philbrowndotcom
    I'm trying to recursively print out all an objects properties and sub-type properties etc. My object model is as follows... type suggestedFooWidget = { value: float ; hasIncreasedSinceLastPeriod: bool ; } type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedFooWidgets = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; totalAbsoluteWidget: suggestedFooWidget ; totalSectorWidget: suggestedFooWidget ; totalExchangeWidget: suggestedFooWidget ; todaysAbsoluteWidget: suggestedFooWidget ; msdAbsoluteWidget: suggestedFooWidget ; msdSectorWidget: suggestedFooWidget ; msdExchangeWidget: suggestedFooWidget ; } And my recursion is based on the following pattern matching... let rec printObj (o : obj) (sb : StringBuilder) (depth : int) let props = o.GetType().GetProperties() let enumer = props.GetEnumerator() while enumer.MoveNext() do let currObj = (enumer.Current : obj) ignore <| match currObj with | :? string as s -> sb.Append(s.ToString()) | :? bool as c -> sb.Append(c.ToString()) | :? int as i -> sb.Append(i.ToString()) | :? float as i -> sb.Append(i.ToString()) | _ -> printObj currObj sb (depth + 1) sb In the debugger I see that currObj is of type string, int, float, etc but it always jumps to the defualt case at the bottom. Any idea why this is happening?

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