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• How do I do multiple has_and_belongs_to_many associations between the same two classes?

  - by Ermin

  I have the following setup: class Publication < ActiveRecord::Base has_and_belongs_to_many :authors, :class_name=>'Person', :join_table => 'authors_publications' has_and_belongs_to_many :editors, :class_name=>'Person', :join_table => 'editors_publications' end class Person < ActiveRecord::Base has_and_belongs_to_many :publications end With this setup I can do stuff like Publication.first.authors. But if I want to list all publications in which a person is involved Person.first.publications, an error about a missing join table people_publications it thrown. How could I fix that? Should I maybe switch to separate models for authors and editors? It would however introduce some redundancy to the database, since a person can be an author of one publication and an editor of another.

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• How to implement a TypeConverter for a type and property I don't own?

  - by CannibalSmith

  This is annoying: <GeometryDrawing> <GeometryDrawing.Pen> <Pen Brush="Black"/> </GeometryDrawing.Pen> </GeometryDrawing> I want this: <GeometryDrawing Pen="Black"/> So I write a TypeConverter: public class PenConverter : TypeConverter { static readonly BrushConverter brushConverter = new BrushConverter(); public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType) { if (sourceType == typeof(string)) return true; return base.CanConvertFrom(context, sourceType); } public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value) { var s = value as string; if (a != null) { var brush = brushConverter.ConvertFromInvariantString(s) as Brush; return new Pen(brush, 1); } return base.ConvertFrom(context, culture, value); } } Now, how do I link it up with the Pen type? I can't just add a TypeConverterAttribute to it as I don't own it (nor do I own GeometryDrawing.Pen property).

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• Algorithm to emulate mouse movement as a human does?

  - by Eye of Hell

  Hello I need to test a software that treats some mouse movements as "gestures". For such a task I need to emulate mouse movement from point A to point B, not in straight line, but as a real mouse moves - with curves, a bit of jaggedyness etc. Is there any available solution (algorithm/code itself, not a library/exe) that I can use? Of course I can write some simple sinusoidal math by myself, but this would be a very crude emulation of a human hand leading a mouse. Perhaps such a task has been solved already numerous times, and I can just borrow an existing code? :)

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• Getting child elements that are related to a parent in same table

  - by Madawar

  I have the following database schema class posts(Base): __tablename__ = 'xposts' id = Column(Integer, primary_key=True) class Comments(Base): __tablename__ = 'comments' id = Column(Integer, primary_key=True) comment_parent_id=Column(Integer,unique=True) #comment_id fetches comment of a comment ie the comment_parent_id comment_id=Column(Integer,default=None) comment_text=Column(String(200)) Values in database are 1 12 NULL Hello First comment 2 NULL 12 First Sub comment I want to fetch all Comments and sub comments of a post using sqlalchemy and have this so far qry=session.query(Comments).filter(Comments.comment_parent_id!=None) print qry.count() Is there a way i can fetch the all the subcomments of a comment in a query i have tried outerjoin on the same table(comments) and it seemed stupid and it failed.

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• Constructor type not found

  - by WaffleTop

  Hello, What I am doing: I am taking the Microsoft Enterprise Library 4.1 and attempting to expand upon it using a few derived classes. I have created a MyLogEntry, MyFormatter, and MyTraceListener which derive from their respective base classes when you remove the "My" from their names. What my problem is: Everything compiles fine. When I go to run a test using Logger.Write(logEntry) it errors right after it initializes MyTraceListener with an error message: "The current build operation (... EnterpriseLibrary.Logging.LogWriter, null]) failed: Constructor on type 'MyLogging.MyFormatter' not found. (Strategy type ConfiguredObjectStrategy, index 2) I figured it was something to do with the constructor so I tried removing it, add it, and adding a call to the base class LogFormatter. Nothing has worked. Does anyone have insight into this problem? Is it maybe a reference issue? Bad App.config configuration? Thank you in advance

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• Unknown attribute xsi:type in XmlSerializer

  - by vanccoon

  I am learning XML Serialization and meet an issue, I have two claess [System.Xml.Serialization.XmlInclude(typeof(SubClass))] public class BaseClass { } public class SubClass : BaseClass { } I am trying to serialize a SubClass object into XML file, I use blow code XmlSerializer xs = new XmlSerializer(typeof(Base)); xs.Serialize(fs, SubClassObject); I noticed Serialization succeed, but the XML file is kind of like ... If I use XmlSerializer xs = new XmlSerializer(typeof(Base)); SubClassObject = xs.Deserialize(fs) as SubClass; I noticed it will complain xsi:type is unknown attribute(I registered an event), although all information embedded in the XML was parsed successfully and members in SubClassObject was restored correctly. Anyone has any idea why there is error in parsing xsi:type and anything I did wrong? Thanks

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• How to create real-life robots?

  - by Click Upvote

  Even before I learnt programming I've been fascinated with how robots could work. Now I know how the underlying programming instructions would be written, but what I don't understand is how those intructions are followed by the robot. For example, if I wrote this code: object=Robot.ScanSurroundings(300,400); if (Objects.isEatable(object)) { Robot.moveLeftArm(300,400); Robot.pickObject(object); } How would this program be followed by the CPU in a way that would make the robot do the physical action of looking to the left, moving his arm, and such? Is it done primarily in binary language/ASM? Lastly, where would i go if I wanted to learn how to create a robot?

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• Strange Java Coding??? Class in class???

  - by poeschlorn

  Hi guys, I got a question about Java coding in general... In some sample codes there are methods and classes declared WITHIN other methods and/or classes.... I've never heard/red about this...what effect does this kind of programming have? Wouldn't it be better to write down classes in a seperate file and methods side by side and not within each other (like every book tells you)? What are the advantages and disadvantages of this kind of programming? Here's an example of what I mean: Handler mHandler = new Handler() { public void handleMessage(android.os.Message msg) { TextView textView = (TextView) findViewById(R.id.description); textView.setText(mRoad.mName + " " + mRoad.mDescription); MapOverlay mapOverlay = new MapOverlay(mRoad, mapView); List<Overlay> listOfOverlays = mapView.getOverlays(); listOfOverlays.clear(); listOfOverlays.add(mapOverlay); mapView.invalidate(); }; };

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• Prevent mapping all public members of a class in Fluent NHibernate

  - by alimbada

  I have a class generated from a WSDL that has a bunch of public properties and a public event. I'm extending this class with my own and adding some properties to it. All of my own properties are declared virtual, but the base class properties are not virtual. I'm using Fluent NHibernate's ClassMap to map only the properties from my extended class. How do I prevent (Fluent)NHibernate from trying to persist all the base class's public members? At the moment, I get the following exception when creating the ISessionFactory: NHibernate.InvalidProxyTypeException: The following types may not be used as proxies: Type: method get_<BaseClassProperty should be 'public/protected virtual' or 'protected internal virtual' Type: method set_<BaseClassProperty should be 'public/protected virtual' or 'protected internal virtual' ... Type: method add_<BaseClassEvent should be 'public/protected virtual' or 'protected internal virtual' Type: method remove_<BaseClassEvent should be 'public/protected virtual' or 'protected internal virtual'

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• Change a Recursive function that has a for loop in it into an iterative function?

  - by Bill

  So I have this function that I'm trying to convert from a recursive algorithm to an iterative algorithm. I'm not even sure if I have the right subproblems but this seems to determined what I need in the correct way, but recursion can't be used you need to use dynamic programming so I need to change it to iterative bottom up or top down dynamic programming. The basic recursive function looks like this: Recursion(i,j) { if(i>j) return 0; else { //This finds the maximum value for all possible subproblems and returns that for this problem for(int x = i; x < j; x++) { if(some subsection i to x plus recursion(x+1,j) is > current max) max = some subsection i to x plus recursion(x+1,j) } } } This is the general idea, but since recursions typically don't have for loops in them I'm not sure exactly how I would convert this to iterative. Does anyone have any ideas?

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• What Use are Threads Outside of Parallel Problems on MultiCore Systesm?

  - by Robert S. Barnes

  Threads make the design, implementation and debugging of a program significantly more difficult. Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system. I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation? Or more succinctly, what kinds of non-performance related problems justify threading? Edit Well I just ran across one instance that's not CPU limited but threads make a big difference: TCP, HTTP and the Multi-Threading Sweet Spot Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

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• Nested attributes form for model which belongs_to few models

  - by ExiRe

  I have few models - User, Teacher and TeacherLeader. class User < ActiveRecord::Base attr_accessible ..., :teacher_attributes has_one :teacher has_one :teacher_leader accepts_nested_attributes_for :teacher_leader end class Teacher < ActiveRecord::Base belongs_to :user has_one :teacher_leader end class TeacherLeader < ActiveRecord::Base belongs_to :user belongs_to :teacher end I would like to fill TeacherLeader via nested attributes. So, i do such things in controller: class TeacherLeadersController < ApplicationController ... def new @user = User.new @teacher_leader = @user.build_teacher_leader @teachers_collection = Teacher.all.collect do |t| [ "#{t.teacher_last_name} #{t.teacher_first_name} #{t.teacher_middle_name}", t.id ] end @choosen_teacher = @teachers_collection.first.last unless @teachers_collection.empty? end end And also have such view (new.html.erb): <%= form_for @user, :url => teacher_leaders_url, :html => {:class => "form-horizontal"} do |f| %> <%= field_set_tag do %> <% f.fields_for :teacher_leader do |tl| %> <div class="control-group"> <%= tl.label :teacher_id, "Teacher names", :class => "control-label" %> <div class="controls"> <%= select_tag( :teacher_id, options_for_select( @teachers_collection, @choosen_teacher )) %> </div> </div> <% end %> <div class="control-group"> <%= f.label :user_login, "Login", :class => "control-label" %> <div class="controls"> <%= f.text_field :user_login, :placeholder => @everpresent_field_placeholder %> </div> </div> <div class="control-group"> <%= f.label :password, "Pass", :class => "control-label" %> <div class="controls"> <%= f.text_field :password, :placeholder => @everpresent_field_placeholder %> </div> </div> <% end %> <%= f.submit "Create", :class => "btn btn-large btn-success" %> <% end %> Problem is that select form here does NOT appear. Why? Do i do something wrong?

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• Multiple Producers Single Consumer Queue

  - by Talguy

  I am new to multithreading and have designed a program that receives data from two microcontroller measuring various temperatures (Ambient and Water) and draws the data to the screen. Right now the program is singly threaded and its performance SUCKS A BIG ONE. I get basic design approaches with multithreading but not well enough to create a thread to do a task but what I don't get is how to get threads to perform seperate task and place the data into a shared data pool. I figured that I need to make a queue that has one consumer and multiple producers (would like to use std::queue). I have seen some code on the gtkmm threading docs that show a single Con/Pro queue and they would lock the queue object produce data and signal the sleeping thread that it is finished then the producer would sleep. For what I need would I need to sleep a thread, would there be data conflicts if i didn't sleep any of the threads, and would sleeping a thread cause a data signifcant data delay (I need realtime data to be drawn 30 frames a sec) How would I go about coding such a queue using the gtkmm/glibmm library.

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• RSS-Feed or XML-Stream?

  - by Maenny

  HI Folks, I am programming a website for online-reservation-management, preferably for holiday homes. I want to implement a service, which allows the user to pass all their occupation dates to other websites. My question is, what would be the most professional way to do this? Generate a XML-stream Create a valid RSS Feed I think that a XML file has the advantages of being straight to the point, without any information that noone needs. Webmasters of other websites surely prefer the structure of a simple XML file. On the other hand, when someone without programming knowledge wants to use the RSS-Feed with a feedreader or simply with the browser, it may be user-friendlier to use a RSS-FEED. What so you think, I'm unsure...? Greetz Maenny

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• How to solve this problem with lists?

  - by osabri

  what i don't understand in my task here what kind of list i can use, and if it should have 2 attributes key and value ? or only value? with pointers to another node ofc the task: "design a function which create a list using input from the keyboard _ the prefered solution. Assume that some magic stops the input; so the length of a list is not known in advance.(alternative solution: a function which creates explicitly a fixed list. However, all other function can not assume any knowledge about the length of lists). Necessary utilities( additional functions to be created): a function which deallocates the memory used for lists and a function which prints the content of the list. let the element of lists contain a letter. Design a function which create a copy of such list. can't also understand the list line !!!!!???

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• Questions about use lib for perl

  - by Tyug

  I use use lib "./DIR" to grab a library from a folder elsewhere. However, it doesn't seem to work on my server, but it works fine on my local desktop. Any particular reasons? And one more question, does use lib get propagated within several modules? Two situations: Say I make a base class that requires a few libraries, but I know that it needs to be extended and the extended class will need to use another library. Can I put the use lib command in the base class? or will I need to put it in every extending class? Finally, can I just have a use package where package contains a bunch of use lib, will it propagate the use lib statements over to my current module? <-- I don't think so, but asking anyways Thanks in advance! Tyug

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• Should old/legacy/unused code be deleted from source control repository?

  - by Checkers

  I've encountered this in multiple projects. As the code base evolves, some libraries, applications, and components get abandoned and/or deprecated. Most people prefer to keep them in. The usual argument is that the code does not really take any space, it can be left alone until needed again. So a repository slowly turns into a cesspool of legacy code, where it's hard to find anything. Some people delete old code, since it creates clutter, raises more questions for new people, and you can restore any old snapshot of the code base anyway. However you can't always find the old code if you don't know where to look, as none of the (common) VCS I know offer search over the entire repository including all historical revisions, and the only way to search the old files is to check out the revision where the deleted file exists. What would be a good approach to repository management?

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• One Controller is Sometimes Bound Twice with Ninject

  - by Dusda

  I have the following NinjectModule, where we bind our repositories and business objects: /// <summary> /// Used by Ninject to bind interface contracts to concrete types. /// </summary> public class ServiceModule : NinjectModule { /// <summary> /// Loads this instance. /// </summary> public override void Load() { //bindings here. //Bind<IMyInterface>().To<MyImplementation>(); Bind<IUserRepository>().To<SqlUserRepository>(); Bind<IHomeRepository>().To<SqlHomeRepository>(); Bind<IPhotoRepository>().To<SqlPhotoRepository>(); //and so on //business objects Bind<IUser>().To<Data.User>(); Bind<IHome>().To<Data.Home>(); Bind<IPhoto>().To<Data.Photo>(); //and so on } } And here are the relevant overrides from our Global.asax, where we inherit from NinjectHttpApplication in order to integrate it with Asp.Net Mvc (The module lies in a separate dll called Thing.Web.Configuration): protected override void OnApplicationStarted() { base.OnApplicationStarted(); //routes and areas AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); //Initializes a singleton that must reference this HttpApplication class, //in order to provide the Ninject Kernel to the rest of Thing.Web. This //is necessary because there are a few instances (currently Membership) //that require manual dependency injection. NinjectKernel.Instance = new NinjectKernel(this); //view model factory. NinjectKernel.Instance.Kernel.Bind<IModelFactory>().To<MasterModelFactory>(); } protected override NinjectControllerFactory CreateControllerFactory() { return base.CreateControllerFactory(); } protected override Ninject.IKernel CreateKernel() { var kernel = new StandardKernel(); kernel.Load("Thing.Web.Configuration.dll"); return kernel; } Now, everything works great, with one exception: For some reason, sometimes Ninject will bind the PhotoController twice. This leads to an ActivationException, because Ninject can't discern which PhotoController I want. This causes all requests for thumbnails and other user images on the site to fail. Here is the PhotoController in it's entirety: public class PhotoController : Controller { public PhotoController() { } public ActionResult Index(string id) { var dir = Server.MapPath("~/" + ConfigurationManager.AppSettings["UserPhotos"]); var path = Path.Combine(dir, id); return base.File(path, "image/jpeg"); } } Every controller works in exactly the same way, but for some reason the PhotoController gets double-bound. Even then, it only happens occasionally (either when re-building the solution, or on staging/production when the app pool kicks in). Once this happens, it continues to happen until I redeploy without changing anything. So...what's up with that?

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• How to discover table properties from SQLAlchemy mapped object

  - by ssaboum

  Hi, My point is i have a class mapped with a table, in my case in a declarative way, and i want to "discover" table properties, columns, names, relations, from this class : engine = create_engine('sqlite:///' + databasePath, echo=True) # setting up root class for declarative declaration Base = declarative_base(bind=engine) class Ship(Base): __tablename__ = 'ships' id = Column(Integer, primary_key=True) name = Column(String(255)) def __init__(self, name): self.name = name def __repr__(self): return "<Ship('%s')>" % (self.name) So now my goal is from the "Ship" class to get the table columns and their properties from another piece of code. I guess i can deal with it using instrumentation but is there any way provided by the SQLAlchemy API ? Thank you.

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• a direct, simple api to run as system?

  - by fejesjoco

  Suppose a program is running with elevated privileges already, and it needs to see the contents of the System Volume Information folder, and by default, only NT Authority\System can do that. A workaround would be to change ACL's on the folder, but I don't want to mess with that. I already found two ways to do it: the task scheduler and psexec. They are too indirect, I don't even need to describe the first one, and the second one works by installing a windows service, running it, telling it to run whatever I wanted to run, then uninstalling the service. Now the question is: is there a direct, simple WinAPI function to run something as system? I don't think that such an API would circumvent the security restrictions, as an administrator I have the right to schedule a task or install a service, so there must be a shortcut.

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• Using Rails and Rspec, how do you test that the database is not touched by a method

  - by Will Tomlins

  So I'm writing a test for a method which for performance reasons should achieve what it needs to achieve without using SQL queries. I'm thinking all I need to know is what to stub: describe SomeModel do describe 'a_getter_method' do it 'should not touch the database' do thing = SomeModel.create something_inside_rails.should_not_receive(:a_method_querying_the_database) thing.a_getter_method end end end EDIT: to provide a more specific example: class Publication << ActiveRecord::Base end class Book << Publication end class Magazine << Publication end class Student << ActiveRecord::Base has_many :publications def publications_of_type(type) #this is the method I am trying to test. #The test should show that when I do the following, the database is queried. self.publications.find_all_by_type(type) end end describe Student do describe "publications_of_type" do it 'should not touch the database' do Student.create() student = Student.first(:include => :publications) #the publications relationship is already loaded, so no need to touch the DB lambda { student.publications_of_type(:magazine) }.should_not touch_the_database end end end So the test should fail in this example, because the rails 'find_all_by' method relies on SQL.

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• ShGetFileInfo called for directory oddity

  - by Axarydax

  Hello, I have a simple file browser and there I display files and folders, obtained by (for directory) SHFILEINFO info = new SHFILEINFO(); SHGetFileInfo(filename, FILE_ATTRIBUTE_DIRECTORY, ref info,Marshal.SizeOf(info), SHGFI_ICON | SHGFI_USEFILEATTRIBUTES | SHGFI_SMALLICON | SHGFI_ADDOVERLAYS); It works 100% fine, but I have noticed an oddity - if I try to obtain an icon for directory, but specify FILE_ATTRIBUTE_NORMAL instead of FILE_ATTRIBUTE_DIRECTORY but it does weird stuff for directories - normal folders have "unknown file type white paper" icons, recycle bin has VLC icon, etc. Directories under SVN have proper overlay, but base file icon (white sheet of paper). I understand that base icon for directory would now be the one of unknown file, but why do some folders have totally strange icon? Config.MSI has installer icon, recycle bin has VLC icon (wtf?!), etc. What does the shell function do with this parameters? Exactly what icon does it obtain? Again, this is not a problem, I'm just curious.

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• LaTeX: Left aligning without extra space between words in tables

  - by goldfrapp04

  Here is the illustrating code: \documentclass[letterpaper, 10pt]{article} \usepackage[margin=1in]{geometry} \usepackage{array} \usepackage[none]{hyphenat} \begin{document} \begin{center} \begin{tabular}{|m{4.5cm}|m{1.2cm}<{\centering}|m{8cm}|c|} \hline \centering \textbf{Course Name} & \centering \textbf{Date} & \centering \textbf{Textbook} & \centering \textbf{Grade} \tabularnewline \hline C Programming Language \& Lab & 09/2009 - 12/2009 & Brian W. Kernighan, and Dennis M. Ritchie, \textit{The C Programming Language}, 2nd ed. ISBN:9780131103627 & 89 \\ \hline Integrative Practice on Courses & 07/2011 & LUPA, \textit{Linux Software Engineer}, ISBN:9787030199645 & 87 \\ \hline \end{tabular} \end{center} \end{document} As shown in the pdf generated, there are too much space between some words because I disabled automatic hyphenation. I'd like to leave only single space between words, without justify align. THANK YOU!

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• ScheduledThreadPoolExecutor executing a wrong time because of CPU time discrepancy

  - by richs

  I'm scheduling a task using a ScheduledThreadPoolExecutor object. I use the following method: public ScheduledFuture<?> schedule(Runnable command, long delay,TimeUnit unit) and set the delay to 30 seconds (delay = 30,000 and unit=TimeUnit.MILLISECONDS). Sometimes my task occurs immediately and other times it takes 70 seconds. I believe the ScheduledThreadPoolExecutor uses CPU specific clocks. When i run tests comparing System.currentTimeMillis(), System.nanoTime() [which is CPU specific] i see the following schedule: 1272637682651ms, 7858346157228410ns execute: 1272637682667ms, 7858386270968425ns difference is 16ms but 4011374001ns (or 40,113ms) so it looks like there is discrepancy between two CPU clocks of 40 seconds How do i resolve this issue in java code? Unfortunately this is a clients machine and i can't modify their system.

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• Commitment to Zend Framework - any arguments against?

  - by Pekka

  I am refurbishing a big CMS that I have been working on for quite a number of years now. The product itself is great, but some components, the Database and translation classes for example, need urgent replacing - partly self-made as far back as 2002, grown into a bit of a chaos over time, and might have trouble surviving a security audit. So, I've been looking closely at a number of frameworks (or, more exactly, component Libraries, as I do not intend to change the basic structure of the CMS) and ended up with liking Zend Framework the best. They offer a solid MVC model but don't force you into it, and they offer a lot of professional components that have obviously received a lot of attention (Did you know there are multiple plurals in Russian, and you can't translate them using a simple ($number == 0) or ($number > 1) switch? I didn't, but Zend_Translate can handle it. Just to illustrate the level of thorougness the library seems to have been built with.) I am now literally at the point of no return, starting to replace key components of the system by the Zend-made ones. I'm not really having second thoughts - and I am surely not looking to incite a flame war - but before going onward, I would like to step back for a moment and look whether there is anything speaking against tying a big system closely to Zend Framework. What I like about Zend: As far as I can see, very high quality code Extremely well documented, at least regarding introductions to how things work (Haven't had to use detailed API documentation yet) Backed by a company that has an interest in seeing the framework prosper Well received in the community, has a considerable user base Employs coding standards I like Comes with a full set of unit tests Feels to me like the right choice to make - or at least, one of the right choices - in terms of modern, professional PHP development. I have been thinking about encapsulating and abstracting ZF's functionality into own classes to be able to switch frameworks more easily, but have come to the conclusion that this would not be a good idea because: it would be an unnecessary level of abstraction it could cost performance the big advantage of using a framework - the existence of a developer base that is familiar with its components - would partly be cancelled out therefore, the commitment to ZF would be a deep one. Thus my question: Is there anything substantial speaking against committing to the Zend Framework? Do you have insider knowledge of plans of Zend Inc.'s to go evil in 2011, and make it a closed source library? Is Zend Inc. run by vampires? Are there conceptual flaws in the code base you start to notice when you've transitioned all your projects to it? Is the appearance of quality code an illusion? Does the code look good, but run terribly slow on anything below my quad-core workstation?

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