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  • Passing data between objects in Chain of Responsibility pattern

    - by AbrahamJP
    While implementing the Chain of Responsibility pattern, i came across a dilemma om how to pass data between objects in the chain. The datatypes passed between object in the chain can differ for each object. As a temporary fix I had created a Static class containing a stack where each object in the chain can push the results to the stack while the next object in the chain could pop the results from the stack. Here is a sample code on what I had implemented. public interface IHandler { void Process(); } public static class StackManager { public static Stack DataStack = new Stack(); } //This class doesn't require any input to operate public class OpsA : IHandler { public IHandler Successor {get; set; } public void Process() { //Do some processing, store the result into Stack var ProcessedData = DoSomeOperation(); StackManager.DataStack.Push(ProcessedData); if(Successor != null) Successor(); } } //This class require input data to operate upon public class OpsB : IHandler { public IHandler Successor {get; set; } public void Process() { //Retrieve the results from the previous Operation var InputData = StackManager.DataStack.Pop(); //Do some processing, store the result into Stack var NewProcessedData = DoMoreProcessing(InputData); StackManager.DataStack.Push(NewProcessedData); if(Successor != null) Successor(); } } public class ChainOfResponsibilityPattern { public void Process() { IHandler ProcessA = new OpsA(); IHandler ProcessB = new OpsB(); ProcessA.Successor = ProcessB; ProcessA.Process(); } } Please help me to find a better approach to pass data between handlers objects in the chain.

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  • [Delphi] How would you refactor this code?

    - by Al C
    This hypothetical example illustrates several problems I can't seem to get past, even though I keep trying!! ... Suppose the original code is a long event handler, coded in the UI, triggered when a user clicks a cell in a grid. Expressed as pseudocode it's: if Condition1=true then begin //loop through every cell in row, //if aCell/headerCellValue>1 then //color aCell red end else if Condition2=true then begin //do some other calculation adding cell and headerCell values, and //if some other product>2 then //color the whole row green end else show an error message I look at this and say "Ah, refactor to the strategy pattern! The code will be easier to understand, easier to debug, and easier to later extend!" I get that. And I can easily break the code into multiple procedures. The problem is ultimately scope related. Assume the pseudocode makes extensive use of grid properties, values displayed in cells, maybe even built-in grid methods. How do you move all that to another unit, without referencing the grid component in the UI--which would break all the "rules" about loose coupling that make OOP valuable? ... I'm really looking forward to responses. Thanks, as always -- Al C.

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  • Modular enterprise architecture using MVC and Orchard CMS

    - by MrJD
    I'm making a large scale MVC application using Orchard. And I'm going to be separating my logic into modules. I'm also trying to heavily decouple the application for maximum extensibility and testability. I have a rudimentary understanding of IoC, Repository Pattern, Unit of Work pattern and Service Layer pattern. I've made myself a diagram. I'm wondering if it is correct and if there is anything I have missed regarding an extensible application. Note that each module is a separate project.

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  • Implementing the procducer-consumer with .NET 4.0 new

    - 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 and enqueuing task items and one other 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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  • How to implement Gradient Opacity (Mask) using html css javascript

    - by brz dot net
    I have to show 25% right screen in such way that the text looks appeared from right. For this I need to set opacity from 0 to 100 at 25% right side screen means rightmost opacity would be 0 and at 75% the opacity would be 100. For this, I took a Div and set opacity but It looks bad because of border. I need to gray out text. It looks a block. Let me know how I can implement cross browser compatible gradient opacity mask for right screen text. What is the best way to do this?

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  • How to check if two records have a self-referencing relation?

    - by Machine
    Consider the following schema with users and their collegues (friends): Users User: columns: user_id: name: user_id as userId type: integer(8) unsigned: 1 primary: true autoincrement: true first_name: name: first_name as firstName type: string(45) notnull: true last_name: name: last_name as lastName type: string(45) notnull: true email: type: string(45) notnull: true unique: true relations: Collegues: class: User local: invitor foreign: invitee refClass: CollegueStatus equal: true onDelete: CASCADE onUpdate: CASCADE Join table: CollegueStatus: columns: invitor: type: integer(8) unsigned: 1 primary: true invitee: type: integer(8) unsigned: 1 primary: true status: type: enum(8) values: [pending, accepted, denied] default: pending notnull: true Now, let's say I two records, one for the user making a HTTP request (the logged in user), and one record for a user he wants to send a message to. I want to check if these users are collegues. Questions: Does Doctrine have any pre-build functionality to check if two records with with self-relations are related? If not, how would you write a method to check this? Where would you put said method? (In the User-class, UserTable-class etc) I could probably do something like this: public function (User $user1, User $user2) { // Ensure we load collegues if $user1 was fetched with DQL that // doesn't load this relation $collegues = $user1->get('Collegues'); $areCollegues = false; foreach($collegues as $collegue) { if($collegue['userId'] === $user2['userId']) { $areCollegues = true; break; } } return $areCollegues; } But this looks a neither efficient nor pretty. I just feel that it should be solved already for self-referencing relations to be nice to use.

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  • Sorting data by relevance, from multiple tables

    - by Oden
    Hey, How is it possible to sort data from multiple tables by relevance? My table structure is following: I have 3 tables in my database, one table contains the name of solar systems, the second for e.g. of planets. There is one more table, witch is a connection between solar systems and planets. If I want to get data of a planet, witch is in the Milky Way, i post this data to the server, and it gives me a multi-dimensional array witch contains: The Milky Way, with every planet in it Every planet, witch name contains the string Milky Way (maybe thats a bat example because i don't think that theres but one planet with this name, but the main concept is on file) But, i want to set the most relevant restaurants to the top of the array. (for the relevance i would check the description of the restaurants or something like that) So, how would you do that kind of data sorting?

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  • I want define tables from a part of my ER Diagram.

    - by M R Jafari
    I have a ER-Diagram (Show in http://www.4freeimagehost.com/show.php?i=f82997ca4d5d.png). In the diagram you see 2 entities and a 1:N relataion together. Project has 2 columns as ProjectID, ProjectName. Employee has 3 colums as EmployeeID, EmployeeName and ProjectID. A project has ONLY 1 project-manager and project-manager is a employee. What columns add them?

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  • Does Javascript have classes?

    - by Glycerine
    A friend and I had an argument last week. He stated there were no such things as classes in Javascript. I said there was as you can say var object = new Object() he says "as there is no word class used. Its not a class. -- Whats your take on it guys? thanks.

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  • Building a professional company website

    - by Sphynx
    Hi fellows, I want to create a professional website for my company. I'm not a designer. I know some html/css, but I don't have much experience making up advanced pages and layouts. I'd expect public area, with various articles, and a "customer zone", accessible via username and password, where clients will be able to track their orders and download files. It needs to look very modern. I don't want to use website templates, because they're too simple. I know some Wordpress, but that's mostly for blogs, and anyways you need to find a right theme besides the CMS itself... Is there any alternative solution, some kind of framework for building such portals? Preferably a system that doesn't require designer skills. Thanks!

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  • c# multi threaded file processing

    - by user177883
    There is a folder that contains 1000 of small text files. I aim to parse and process all of them while more files are being populated in to the folder. My intention is to multithread this operation as the single threaded prototype took 6 minutes to process 1000 files. I like to have reader and writer thread(s) as following : while the reader thread(s) are reading the files, I d like to have writer thread(s) to process them. Once the reader is started reading a file, I d like to mark it as being processed, such as by renaming it, once it s read, rename it to completed. How to approach such multithreaded application ? Is it better to use a distributed hash table or a queue? Which data structure to use that would avoid locks? Would you have a better approach to this scheme that you like to share?

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  • How to color textblock on mouse over?

    - by DeanMc
    I'm looking to see if there is a way to change the color of a textblock in silverlight on mouse over. I have tried a trigger which I read now doesn't work. I would like to avoid having to do it in the codebehind if at all possible.

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  • Immutable classes in C++

    - by ereOn
    Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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  • MySQL forgot about automatically creating an index for a foreign key?

    - by bobo
    After running the following SQL statements, you will see that, MySQL has automatically created the non-unique index question_tag_tag_id_tag_id on the tag_id column for me after the first ALTER TABLE statement has run. But after the second ALTER TABLE statement has run, I think MySQL should also automatically create another non-unique index question_tag_question_id_question_id on the question_id column for me. But as you can see from the SHOW INDEXES statement output, it's not there. Why does MySQL forget about the second ALTER TABLE statement? By the way, since I have already created a unique index question_id_tag_id_idx used by both question_id and tag_id columns. Is creating a separate index for each of them redundant? mysql> DROP DATABASE mydatabase; Query OK, 1 row affected (0.00 sec) mysql> CREATE DATABASE mydatabase; Query OK, 1 row affected (0.00 sec) mysql> USE mydatabase; Database changed mysql> CREATE TABLE question (id BIGINT AUTO_INCREMENT, html TEXT, PRIMARY KEY(id)) ENGINE = INNODB; Query OK, 0 rows affected (0.05 sec) mysql> CREATE TABLE tag (id BIGINT AUTO_INCREMENT, name VARCHAR(10) NOT NULL, UNIQUE INDEX name_idx (name), PRIMARY KEY(id)) ENGINE = INNODB; Query OK, 0 rows affected (0.05 sec) mysql> CREATE TABLE question_tag (question_id BIGINT, tag_id BIGINT, UNIQUE INDEX question_id_tag_id_idx (question_id, tag_id), PRIMARY KEY(question_id, tag_id)) ENGINE = INNODB; Query OK, 0 rows affected (0.00 sec) mysql> ALTER TABLE question_tag ADD CONSTRAINT question_tag_tag_id_tag_id FOREIGN KEY (tag_id) REFERENCES tag(id); Query OK, 0 rows affected (0.10 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE question_tag ADD CONSTRAINT question_tag_question_id_question_id FOREIGN KEY (question_id) REFERENCES question(id); Query OK, 0 rows affected (0.13 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> SHOW INDEXES FROM question_tag; +--------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | +--------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ | question_tag | 0 | PRIMARY | 1 | question_id | A | 0 | NULL | NULL | | BTREE | | | question_tag | 0 | PRIMARY | 2 | tag_id | A | 0 | NULL | NULL | | BTREE | | | question_tag | 0 | question_id_tag_id_idx | 1 | question_id | A | 0 | NULL | NULL | | BTREE | | | question_tag | 0 | question_id_tag_id_idx | 2 | tag_id | A | 0 | NULL | NULL | | BTREE | | | question_tag | 1 | question_tag_tag_id_tag_id | 1 | tag_id | A | 0 | NULL | NULL | | BTREE | | +--------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 5 rows in set (0.01 sec) mysql>

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  • Are there any MVP Frameworks projects out there?

    - by Greg Malcolm
    MVC is used a number of popular frameworks. To name just a few, Ruby on Rails, ASP.NET MVC, Monorail, Spring MVC. Are there any equivalent frameworks using any variant of MVP? Most of the examples I've found online seem to be custom implementations of the pattern rather than reusable frameworks. Suggestions need not be specific to any particular programming language, my interest is mostly academic.

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  • Shipping jar with default .properties file configurations

    - by Maxim Veksler
    Hello, I would like to include a default default.properties file in my .jar library. The idea is to allow the user to override my default is he so desires. I'm having trouble getting the classloader to play nicely with this setup, I've tried to look a at popular jars such as log4j, common-* and others and it seems that no one is implementing this idea. Am I going the wrong way? The second best thing is hard coding the values, and using the default if no .properties key has been found, but this sound oh so wrong. Suggestions?

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  • Questions about .NET CollectionEditor type

    - by smwikipedia
    Who can tell me the internal working mechanism of a CollectionEditor in plain English? I have implemented every virtual function and step into each of them. Still got no clue of its intended algorithm. I searched the web and found tons of compaints about the CollectionEditor type, and even bugs. I am kind of thinking of the CollectionEditor as a total mess.

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  • multiple classes with same methods - best pattern

    - by Tony
    I have a few classes in my current project where validation of Email/Website addresses is necessary. The methods to do that are all the same. I wondered what's the best way to implement this, so I don't need to have these methods copy pasted everywhere? The classes themselves are not necessarily related, they only have those validation methods in common.

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  • How do you create your own drag-n-drop GUI designer ?

    - by panzerschreck
    Hello I was looking at creating a UI for developing web forms, similar to the Netbeans Visual JSF form designer.It will be targeted to use GWT/GXT components.I am looking at a look very similar to VS/Netbeans. Any thoughts on where/how to start ? Initially, I would prefer to have it as a standalone application, later develop it as eclipse plugin. I have already evaluated the extjs designer and the eclipse plugin from instantiations, but i would prefer to have it developed on my own, as it looks challenging, Also, I have few custom components that have been developed. Thanks

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  • Java compilers or JVM languages that support goto?

    - by unknown
    Is there a java compiler flag that allows me to use goto as a valid construct? If not, are there any third-party java compilers that supports goto? If not, are there any other languages that support goto while at the same time can easily call methods written in Java? The reason is I'm making a language that is implemented in Java. Gotos are an important part of my language; I want to be able to compile it to native or JVM bytecode, although it has to be able to easily use Java libraries (ie. C supports goto, but to use it I'd have to rewrite the libraries in C). I want to generate C or Java, etc source files, and not bytecode or machine code. I'm using a third-party compiler to do that.

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  • Cocoa framework development: sharing between projects

    - by e.James
    I am currently developing a handful of similar Cocoa desktop apps. In an effort to share code between them, I have identified a set of core classes and functions that can be common across all of these applications. I would like to bundle this common code into a framework which all of my current applications (and any future ones) can link against. Now, here's the hard part: I'm going to be developing this framework as I go, so I need each of my desktop apps to have a reference to it, but I want to be able to edit the framework source code from within each of the app projects and have the framework automatically rebuilt as required. For example, let's say I have the Xcode project for DesktopAppNumberOne open, and I decide that one of my framework classes needs to be changed. I would like to: Open and edit the source file for that framework class without having to open the framework project in Xcode. Hit "build" on DesktopAppNumberOne, and see the framework rebuilt first (because one of its sources has changed), then see parts of DesktopAppNumberOne rebuilt (because one of the frameworks it links against has changed). I can see how to do this with only one app and one framework, but I'm having trouble figuring out how to do it with multiple apps that share a single framework. Has anyone had success with this approach? Am I perhaps going about this the wrong way? Any help would be appreciated.

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  • Find and replace table/field names in Access?

    - by richardtallent
    I've been handed a rather large, old, and crusty Access 2000/2003 database to clean up. I'll need to rename a number of tables and fields, but need to do so in a way that doesn't break existing queries. (Fortunately, there are no macros, forms, or reports to worry about.) I've heard there are some commercial tools to make this job easier, but only found one (http://www.rickworld.com/products.html). Can anyone recommend this software, or any alternatives?

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  • How to implement Auto_Increment per User, on the same table?

    - by Jonas
    I would like to have multiple users that share the same tables in the database, but have one auto_increment value per user. I will use an embedded database, JavaDB and as what I know it doesn't support this functionality. How can I implement it? Should I implement a trigger on inserts that lookup the users last inserted row, and then add one, or are there any better alternative? Or is it better to implement this in the application code? Or is this just a bad idea? I think this is easier to maintain than creating new tables for every user. Example: table +----+-------------+---------+------+ | ID | ID_PER_USER | USER_ID | DATA | +----+-------------+---------+------+ | 1 | 1 | 2 | 3454 | | 2 | 2 | 2 | 6567 | | 3 | 1 | 3 | 6788 | | 4 | 3 | 2 | 1133 | | 5 | 4 | 2 | 4534 | | 6 | 2 | 3 | 4366 | | 7 | 3 | 3 | 7887 | +----+-------------+---------+------+ SELECT * FROM table WHERE USER_ID = 3 +----+-------------+---------+------+ | ID | ID_PER_USER | USER_ID | DATA | +----+-------------+---------+------+ | 3 | 1 | 3 | 6788 | | 6 | 2 | 3 | 4366 | | 7 | 3 | 3 | 7887 | +----+-------------+---------+------+ SELECT * FROM table WHERE USER_ID = 2 +----+-------------+---------+------+ | ID | ID_PER_USER | USER_ID | DATA | +----+-------------+---------+------+ | 1 | 1 | 2 | 3454 | | 2 | 2 | 2 | 6567 | | 4 | 3 | 2 | 1133 | | 5 | 4 | 2 | 4534 | +----+-------------+---------+------+

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