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• Immutability of big objects

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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• Problem with assigning elements of a class array to individual variables in MATLAB

  - by Marc

  This is a bit of a duplicate of this question, this question, and this question, however those solutions don't work, so I'm asking mine. I've got an array of locally defined classes and I'd like to assign it to multiple, individual variables. This pattern doesn't work: %a is 2x1 of MyClass temp = mat2cell(a); [x,y] = temp{:}; %throws: ??? Insufficient number of outputs from right hand side of equal sign to satisfy assignment. Because temp is a single cell, with my 2x1 array in one cell, rather than a 2x1 cell array with one element of each of my original array in one cell. Any ideas?

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• ASP.NET 4.0 webforms routing

  - by Ethan

  I have an existing site that I'd like to convert to use routing, and after reading Scott Guthrie's post here, I built a working sample that works for most circumstances. However, since not all of the pages on the existing site match a particular pattern, I'll need to check against a database to determine which route (destination .aspx page) to use. For example, most pages are like this: http://www.mysite.com/people/person.html This is fine - I can easily route these to the view_person.aspx page because of the 'people' directory. But some pages are like this: http://www.mysite.com/category_page.html http://www.mysite.com/product_page.html This necessitates checking the database to see whether to route to the view_category.aspx page or the view_product.aspx page. And this is where I'm stuck. Do I create an IRouteHandler that checks the database and returns the route? Or is there a better way? The only code I've found that kind of fits is the answer to this question. Thanks in advance.

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• How can I dynamically inject code to event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• MVVM View reference to ViewModel

  - by BrettRobi

  I'm using MVVM in a WPF app. I'm very new to both. Let me state that I am not a purest in the MVVM pattern, I am trying to use as many best practices as I can but am trying to make what I think are reasonable compromises to make it work in our environment. For example, I am not trying to achieve 0% code in my View codebehind. I have a couple of questions about best practices. 1) I understand I don't want my VM to know about the attached View, but is it reasonable for the View to have a reference to its VM? 2) If a control in a View opens another View (such as a dialog) should I handle this in the View? It seems wrong to handle it in the VM since then the VM has some knowledge of a specific View.

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• Cocos2d: is it good practice to use a shared GameScene when having various levels?

  - by mm24

  In my code (based on the ShootEmUp example in this book, which I highly reccomend, source code in chapter 8 available here) I often use the trick of accessing the GameScene via: +(GameScene*) sharedGameScene; which returns a reference to the static instance of GameScene. Is a static instance of GameScene as in the book still a valid pattern in case I want a MainMenu calling GameScene initialized with different level data each time (e.g. different enemies)? (I have created a sceneWithId:(int) method where I load different level data each time. Or should I pheraps create a GameScene class and then sublcass it? E.g. FirstGameScene : GameScene

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• Making a rectangular selection in a RichTextBox with Alt-Left-Mouse sweep?

  - by Harold Bamford

  There are quite a few applications that allow you to select a box or rectangle of text by sweeping with mouse while the Alt key is pressed. Visual Studio 2010 does this in the code editor, for instance. Emacs does it. Winword does it. We've all seen it. It seems like there must be a standard pattern to follow to encode this behavior but I cannot seem to find it. I suspect I am not Googling with the correct keywords as all I am getting are false hits on rectangle, Alt-Left, sweep, selection, etc. I'm sure I can code it up but it would mean disabling the normal selection code used in, say, RichTextBox. And that sounds ugly, error prone and probably more work than it is worth. Anybody have a suggestion (be nice! :-) ) of how to do this or an example of how it is done?

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• Best programming novel to take on holiday

  - by Ed Guiness

  I am about enjoy a two week break in Spain where I expect to have lots of time for relaxing and reading. I normally read a lot of non-fiction so I'm looking for novel suggestions. If there is another Cryptonomicon out there I'd love to hear about it! UPDATE: In the end I took four books including Quicksilver. Quicksilver was fantastic and I look forward to continuing the series. I was disappointed with Gen X (Coupland) and Pattern Recognition (Gibson). Upon arrival I also found The Monsters Of Gramercy Park (Leigh) which was enjoyable though sad. Thanks for all the recommendations, I'm sure to return to this list when I have more free time.

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• Can you use data binding with the Content property of a WPF Frame?

  - by dthrasher

  I can use data binding to set the initial Content of a WPF Frame, but subsequent changes to the the bound property (implemented using INotifyPropertyChange) do not seem to change the content. Also, does anyone know if binding directly to the Content property in this way will cause the bound item to appear in the Frame or NavigationWindow's journal? Some context: I realize that I should probably be using the NavigationService to interact with the Frame, but I'm attempting to follow the MVVM pattern. It seems like it would be much simpler to databind to the Content property...

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• Is there any benefit to declaring a private property with a getter and setter?

  - by AmoebaMan17

  I am reviewing another developer's code and he has written a lot of code for class level variables that is similar to the following: /// <summary> /// how often to check for messages /// </summary> private int CheckForMessagesMilliSeconds { get; set; } /// <summary> /// application path /// </summary> private string AppPath { get; set; } Doesn't coding this way add unnecessary overhead since the variable is private? Am I not considering a situation where this pattern of coding is required for private variables?

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• database vs flat file, which is a faster structure for regex matching with many simultaneous request

  - by Jamex

  Hi, which structure returns faster result and/or less taxing on the host server, flat file or database (mysql)? Assume many users (100 users) are simultaneously query the file/db. Searches involve pattern matching using regex against a static file/db. File has 50,000 unique lines (same data type). There could be many matches. There is no writing to the file/db, just read. Is it possible to have a duplicate the file/db and write a logic switch to use the backup file/db if the main file is in use? Which language is best for the type of structure? Perl for flat and PHP for db? TIA

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• Intersection of sets Mongodb

  - by afvasd

  Hi everyone I am new to mongo, this is my db design: product := { name: str group: ref, comments: [ ref, ref, ref, ref ] } comments := { ... a bunch of comments stuff } tag := { _id: int, #Need this for online requests tag: str, products: [ {product: ref, score: float}, ... ], comments: [ {comment: ref, score: float}, ...], } So my usage pattern is: GIVEN a product, find comments that have certain tag and sort them accordingly. My current approach involves: Look for that tag object that has tag=myTag pull all the comments out, sorted look for that product where product.name=myProduct pull all the comments out (which are dbrefs by the way) loop through the result of 2, and checking if they are in 4, (this I can do a limit 10) etc. It's pretty inefficient. Any better methods?

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• Expand in linq not loading inner data collections from service.

  - by Kit

  I am seeing odd behavior with service queries! I am using MVVM pattern for a silverlight 3 app on 3.5 framework and Dataservices 1.5. The following code eager loads correctly the parent object and the child heirarchy perfectly IF and ONLY IF I am preloading the data. But I would like to fetch a different set of the parent object (and its child heirarchy) on different button clicks. What I am seeing is that on button click, only the parent object is retrieved, and the child heirarchy contains nothing. Any suggestions? Any ideas how to tackle this? Thanks all. The method: DataServiceQuery serviceQuery = (DataServiceQuery)(from m1 in dbEntities.gis_Region.Expand("gis_RegionValue/gis_Measure") where m1.RegionGuid == new Guid(regionGuid) select m1); serviceQuery.BeginExecute(GetRegionDetailAsyncResult, serviceQuery); The wired Async Result: DataServiceQuery query = (DataServiceQuery)result.AsyncState; gis_Region region = query.EndExecute(result).First();

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• creative way for implementing Data object with it's corespanding buisness logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity reasons lets call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I loose my hierarchy freedom, does any of you have any creative solution for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• GUI system architecture?

  - by topright

  I'm designing GUI (graphical user interface) system for a game engine (C++). Idea is to create a heirarchy of GUI controllers like Focusable, Hoverable, Dragable etc. Every GUI component can attach multiple controllers, they modify component's behaviour. I think it gives flexible system and protects from code duplication. Different instances of the same GUI class can have different complex behaviours (may be, even change it dynamically), so this approach looks practical. The other choice is to add focused, hovered, dragged etc. flags in the base GUI component class. It looks like overhead and not that flexible. Another solution is to use Decorator pattern and wrap objects with FocusDecorator, HoverDecorator etc. Maintaining such system looks a bit harder. Question: What are pitfalls in my solution? May be you have seen a better approaches in GUI systems? What are the best ways of implementing such flexible complex system?

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• emacs: inverse search

  - by Data

  Is there a way to do a inverse search? I have very big log file where a particular pattern fills up for few dozen pages 20100414 alpha beta 20100414 alpha beta <few dozen pages> 20100414 alpha beta 20100414 gamma delta 20100414 gamma delta <few dozen pages> 20100414 gamma delta Problem is, I don't know what text would be after "alpha beta". It could be "gamma delta" or something else. So I would like to skip all the lines that contain "alpha beta".

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• what happens to running/blocked runnables when executorservice is shutdown()

  - by prmatta

  I posted a question about a thread pattern today, and almost everyone suggested that I look into the ExecutorService. While I was looking into the ExecutorService, I think I am missing something. What happens if the service has a running or blocked threads, and someone calls ExecutorService.shutdown(). What happens to threads that are running or blocked? Does the ExecutorService wait for those threads to complete before it terminates? The reason I ask this is because a long time ago when I used to dabble in Java, they deprecated Thread.stop(), and I remember the right way of stopping a thread was to use sempahores and extend Thread when necessary: public void run () { while (!this.exit) { try { block(); //do something } catch (InterruptedException ie) { } } } public void stop () { this.exit = true; if (this.thread != null) { this.thread.interrupt(); this.thread = null; } } How does ExecutorService handle running threads?

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• Using Regex to remove Carriage Returns in a CSV file in Notepad++

  - by Barry

  I have a CSV file I need to clean up. This is a one-time thing so I'd like to do it in Notepad++ if possible. The CSV file has two fields, one of which is wrapped in quotes. I'd like to remove any Carriage Returns from within the quoted field. I was trying to use this pattern but can't get it quite right... (.*)\"(.*)\n(.*)\"(.*) Also correct me if I am wrong, but I presume the "replace with" value would be something along the lines of: \1\2\3\4 Thanks in advance. I'm also open to alternate solutions such as a quick and dirty PERL script.

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• Rails: common approach for handling exceptions in restful actions on objects that have been destroye

  - by Greg

  It is very common in Rails for an objects_controller controller to have RESTful edit and destroy actions like so: def edit @object = Object.find(params[:id]) end def destroy @object = Object.find(params[:id]) @object.destroy redirect_to :back end With an associated view that provides edit and destroy links like so: <%= link_to "Edit the Object", edit_object_path(object) %> <%= link_to "Delete", object, :confirm => 'Are you sure?', :method => :delete %> And it is easy to blow this up. If I open two browser windows, A and B, destroy an object with the "Delete" link in browser A and then press the "Edit" link in browser B, the find() in the edit action throws an exception. Obviously there are several ways to deal with this in the edit action: catch the exception and recover gracefully use @object = find(:first, "conditions... etc. and test the @object before going further But seeing as this is such a common pattern, I would love to know how other folks deal with this situation.

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• How to keep historic details of modification in a database (Audit trail)?

  - by mada

  I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects things are more difficult. So we have, speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that?

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• Inconsistent MySQL COLLATE errors across databases

  - by Teflon Ted

  I have two physically-separate MySQL databases on which I have to run a single query. The query has a section of SQL that looks like this: and foo_table.bar_column like concat('%', rules.pattern, '%') COLLATE utf8_general_ci It runs fine on database A but on database B I get this error: ERROR 1253 (42000): COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'latin1' If I remove the collation it runs fine on database B but on database A I get this error: ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation 'like' Is there a version of the query that will run on both databases? Or, is there a configuration I can change on either database to make the query happy in both places? Update: Database A is version 5.1.38, Database B is version 5.1.34

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• When and why will an OS initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?

  - by LeopardSkinPillBoxHat

  I know that the OS will sometimes initialise memory with certain patterns such as 0xCD and 0xDD. What I want to know is when and why this happens. When Is this specific to the compiler used? Do malloc/new and free/delete work in the same way with regard to this? Is it platform specific? Will it occur on other operating systems, such as Linux or VxWorks? Why My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions. Can you give any practical examples as to how this initialisation is useful? I remember reading something (maybe in Code Complete 2) that it is good to initialise memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger. How portable is this?

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• Image reflection in Silverlight 4

  - by Phani Kumar PV

  I am developing a product scrolling feature where products info( product image, Name, price)will be shown side by side horizontally. i need to show the image of the product and also its reflection. under the reflected image i need to show the Prod Name and its price. The problem here is i dont want to show the complete reflected image. the oputput should be something like this Image Height-100% Reflected Image Height-20% Product name Product Price The above pattern will repeat horizontally. I am able to get the desired output with some problem. The reflected image is shown up with hieght 100% and the sapce between the actual image and product name is very high. My reflected image should be a rotated image of the actual image and only half part of the actual image should be shown. Any pointers even is highly appreciated

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