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  • How Do I Prevent Rails From Treating Updated Nested Attributes Differently From New Nested Attribute

    - by James
    I am using rails3 beta3 and couchdb via couchrest. I am not using active record. I want to add multiple "Sections" to a "Guide" and add and remove sections dynamically via a little javascript. I have looked at all the screencasts by Ryan Bates and they have helped immensely. The only difference is that I want to save all the sections as an array of sections instead of individual sections. Basically like this: "sections" => [{"title" => "Foo1", "content" => "Bar1"}, {"title" => "Foo2", "content" => "Bar2"}] So, basically I need the params hash to look like that when the form is submitted. When I create my form I am doing the following: <%= form_for @guide, :url => { :action => "create" } do |f| %> <%= render :partial => 'section', :collection => @guide.sections %> <%= f.submit "Save" %> <% end %> And my section partial looks like this: <%= fields_for "sections[]", section do |guide_section_form| %> <%= guide_section_form.text_field :section_title %> <%= guide_section_form.text_area :content, :rows => 3 %> <% end %> Ok, so when I create the guide with sections, it is working perfectly as I would like. The params hash is giving me a sections array just like I would want. The problem comes when I want edit guide/sections and save them again because rails is inserting the id of the guide in the id and name of each form field, which is screwing up the params hash on form submission. Just to be clear, here is the raw form output for a new resource: <input type="text" size="30" name="sections[][section_title]" id="sections__section_title"> <textarea rows="3" name="sections[][content]" id="sections__content" cols="40"></textarea> And here is what it looks like when editing an existing resource: <input type="text" value="Foo1" size="30" name="sections[cd2f2759895b5ae6cb7946def0b321f1][section_title]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_section_title"> <textarea rows="3" name="sections[cd2f2759895b5ae6cb7946def0b321f1][content]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_content" cols="40">Bar1</textarea> How do I force rails to always use the new resource behavior and not automatically add the id to the name and value. Do I have to create a custom form builder? Is there some other trick I can do to prevent rails from putting the id of the guide in there? I have tried a bunch of stuff and nothing is working. Thanks in advance!

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  • What's the real benefit of meta-modeling?

    - by Jakob
    After reading several texts about meta-modeling I still do not really get the practical benefit. Sometimes I think it is only an interesting mind game but no useful tool. Sure it is wise to clarify your modeling vocabulary: some may say class where others say entity or concept, but this is just simple documentation your modeling terminology. Meta-modeling, as I understand it, is more complex, as it tries to formalize and abstract modeling. Some good examples are Keet's formal comparison of conceptual data modeling languages (UML, ERM and ORM) from academia and the Meta Object Facility (MOF) from industry. To me MOF looks as impractical as CORBA, which was also created by OMG. In theory you could use meta-modeling to transform and integrate models in different modeling languages, but is anyone actually doing this?

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  • Pass a variable to a Symfony Form

    - by Juan Besa
    Hi, I am building a web application using Symfony 1.4 and Doctrine for a school and I want to make a very simple form to add a course to a student. The main problem I have is that in the drop down list I only want to show the courses in which the student is currently not enrolled. I already have a function in the model (in Student.class.php) which returns all the courses in which the student is not enrolled but the problem is I don't know how to pass the student to the configure() of the form. I have tried several options like passing it with the constructor of the form to a global variable or a special set method but none of them have worked. Is there any form to pass the student to the configure() method? Thanks!

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  • VB.Net how to wait for a different form to close before continuing on.

    - by Sean P
    I have a little log in screen that pops up if a user selects a certain item on my main form. How do I get my code to stop executing til my log in form closes? This is what I am doing so far. Basically i want o execute the code after MyLogin closes. BMSSplash.MyLogin.Show() If isLoggedIn Then BMSSplash.MyBuddy.Show() Cursor.Current = Cursors.WaitCursor End If

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  • Abstract Data Type and Data Structure

    - by mark075
    It's quite difficult for me to understand these terms. I searched on google and read a little on Wikipedia but I'm still not sure. I've determined so far that: Abstract Data Type is a definition of new type, describes its properties and operations. Data Structure is an implementation of ADT. Many ADT can be implemented as the same Data Structure. If I think right, array as ADT means a collection of elements and as Data Structure, how it's stored in a memory. Stack is ADT with push, pop operations, but can we say about stack data structure if I mean I used stack implemented as an array in my algorithm? And why heap isn't ADT? It can be implemented as tree or an array.

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  • Rails 3 Authenticity Token

    - by matsko
    Does anyone know how the authenticity token is managed in rails 3? With all the unobtrusive javascript rails 3 articles showing how the html5 data attributes are used I don't see the authenticity token anywhere.

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  • Is there a more intelligent way to do this besides a long chain of if statements or switch?

    - by Harrison Nguyen
    I'm implementing an IRC bot that receives a message and I'm checking that message to determine which functions to call. Is there a more clever way of doing this? It seems like it'd quickly get out of hand after I got up to like 20 commands. Perhaps there's a better way to abstract this? public void onMessage(String channel, String sender, String login, String hostname, String message){ if (message.equalsIgnoreCase(".np")){ // TODO: Use Last.fm API to find the now playing } else if (message.toLowerCase().startsWith(".register")) { cmd.registerLastNick(channel, sender, message); } else if (message.toLowerCase().startsWith("give us a countdown")) { cmd.countdown(channel, message); } else if (message.toLowerCase().startsWith("remember am routine")) { cmd.updateAmRoutine(channel, message, sender); } }

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  • Why doesn't Haskell have type-level lambda abstractions?

    - by Petr Pudlák
    Are there some theoretical reasons for that (like that the type checking or type inference would become undecidable), or practical reasons (too difficult to implement properly)? Currently, we can wrap things into newtype like newtype Pair a = Pair (a, a) and then have Pair :: * -> * but we cannot do something like ?(a:*). (a,a). (There are some languages that have them, for example, Scala does.)

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  • Problem with date_select when using :discard option. (Rails)

    - by MikeH
    I'm using a date_select with the option :discard_year => true If a user selects a date in the date select, and then he comes back and returns the select to the prompt values of Month and Day, Rails automatically sets the select values to January 1. I know this is the intended functionality if a month is selected and a day is left blank, but that's not the case here. In my example, the user sets both the month and day back to the prompt. By Rails forcing January 1, I'm getting bad results. I've tried every parameter available in the api. :default = nil, :include_blank = true. None of those change the behavior I'm describing. I've isolated the root of the problem, which is this: Because I'm discarding the :year parameter, when the user tries to return the month and day to the prompt values, Rails doesn't see an empty prompt select. It perhaps sees a year selected with empty month and day, which it then sets to January 1. This is the case because the :discard_year parameter does in fact set a date in the database, it just removes it from the view. How can I code around this problem?

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  • Problem accessing variable in a nested form partial

    - by brad
    I have a nested form in a rails view that is called like this <% f.fields_for :invoice_item_numbers do |item_no_form| %> <%= render 'invoice_item_number', :f => item_no_form %> <% end %> and the partial (_invoice_item_number.html.erb) looks like this <div class='invoice_item_numbers'> <% if f.object.new_record? %> <li><%= f.label :item_number %><%= f.text_field :item_number %> <%= link_to_function "remove", "$(this).parent().remove()", :class => 'remove_link' %></li> <% else %> <li class="inline"><%= f.label :item_number %><%= f.text_field :item_number %> </li><li class="inline"><%= f.label :description %><%= invoice_item_number.description %></li><li><%= f.label :amount %><%= f.text_field :amount %> <%= f.check_box '_destroy', :class => 'remove_checkbox' %> <%= f.label '_destroy', 'remove', :class => 'remove_label' %></li> <% end %> </div> This fails with the error message undefined method `description' for nil:NilClass Why does invoice_item_number return a nil object in this partial? It is obviously being defined somehow because if I change it to something else (e.g. item_number.description then the error message becomes undefined local variable or methoditem_number' for #instead. The invoice_item_number object that is being displayed by this partial is being used perfectly well by the form helpers as<%= f.text_field :item_number %and<% f.text_field :amount %both work perfectly well. I have tried a number of solutions such as using@invoice_item_number` and explicitly defining an object in the render method but these have not worked. Presumably there is a very simple answer to this.

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  • Is there a canonical book on general abstractions and modeling?

    - by David The Man
    I've been trying to understand the fundamentals of general abstractions and modeling: there are quite a lot of books when you search for abstractions, but most of those seem to be about learning object-oriented programming in a given language. Is there a book out there that's the de-facto standard for describing best practices, design methodologies, and other helpful information about general abstractions and modeling? What about that book makes it special?

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  • How to prevent Visual Studio setting my default font sizes in an inherited control

    - by Colin
    I have a base class for all my textboxes and I want to set the default font in that class. So I started with this: public partial class MyTextBox : TextBox { public WmlTextBox() { InitializeComponent(); //Font for the whole application can be altered in the Appearance class Font = new Appearance().TextBoxFont; } } I then stripped out all the code in the form that was setting the font of the textboxes. Of course this worked fine until I altered an item on the page. Visual Studio picked up the default font for the application (set in the Appearance class), and generated code in the designer for all TextBoxes to set it to that specific font. How can I stop visual studio from generating code from my default font? I want to allow the developers to change the property, but I want to set the default font centrally.

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  • Is dependency injection by hand a better alternative to composition and polymorphism?

    - by Drake Clarris
    First, I'm an entry level programmer; In fact, I'm finishing an A.S. degree with a final capstone project over the summer. In my new job, when there isn't some project for me to do (they're waiting to fill the team with more new hires), I've been given books to read and learn from while I wait - some textbooks, others not so much (like Code Complete). After going through these books, I've turned to the internet to learn as much as possible, and started learning about SOLID and DI (we talked some about Liskov's substitution principle, but not much else SOLID ideas). So as I've learned, I sat down to do to learn better, and began writing some code to utilize DI by hand (there are no DI frameworks on the development computers). Thing is, as I do it, I notice it feels familiar... and it seems like it is very much like work I've done in the past using composition of abstract classes using polymorphism. Am I missing a bigger picture here? Is there something about DI (at least by hand) that goes beyond that? I understand the possibility of having configurations not in code of some DI frameworks having some great benefits as far as changing things without having to recompile, but when doing it by hand, I'm not sure if it's any different than stated above... Some insight into this would be very helpful!

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  • How Do I Prevent Rails From Treating Edit Fields_For Differently From New Fields_For

    - by James
    I am using rails3 beta3 and couchdb via couchrest. I am not using active record. I want to add multiple "Sections" to a "Guide" and add and remove sections dynamically via a little javascript. I have looked at all the screencasts by Ryan Bates and they have helped immensely. The only difference is that I want to save all the sections as an array of sections instead of individual sections. Basically like this: "sections" => [{"title" => "Foo1", "content" => "Bar1"}, {"title" => "Foo2", "content" => "Bar2"}] So, basically I need the params hash to look like that when the form is submitted. When I create my form I am doing the following: <%= form_for @guide, :url => { :action => "create" } do |f| %> <%= render :partial => 'section', :collection => @guide.sections %> <%= f.submit "Save" %> <% end %> And my section partial looks like this: <%= fields_for "sections[]", section do |guide_section_form| %> <%= guide_section_form.text_field :section_title %> <%= guide_section_form.text_area :content, :rows => 3 %> <% end %> Ok, so when I create the guide with sections, it is working perfectly as I would like. The params hash is giving me a sections array just like I would want. The problem comes when I want edit guide/sections and save them again because rails is inserting the id of the guide in the id and name of each form field, which is screwing up the params hash on form submission. Just to be clear, here is the raw form output for a new resource: <input type="text" size="30" name="sections[][section_title]" id="sections__section_title"> <textarea rows="3" name="sections[][content]" id="sections__content" cols="40"></textarea> And here is what it looks like when editing an existing resource: <input type="text" value="Foo1" size="30" name="sections[cd2f2759895b5ae6cb7946def0b321f1][section_title]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_section_title"> <textarea rows="3" name="sections[cd2f2759895b5ae6cb7946def0b321f1][content]" id="sections_cd2f2759895b5ae6cb7946def0b321f1_content" cols="40">Bar1</textarea> How do I force rails to always use the new resource behavior and not automatically add the id to the name and value. Do I have to create a custom form builder? Is there some other trick I can do to prevent rails from putting the id of the guide in there? I have tried a bunch of stuff and nothing is working. Thanks in advance!

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  • Abstract Factory Method and Polymorphism

    - by Scotty C.
    Being a PHP programmer for the last couple of years, I'm just starting to get into advanced programming styles and using polymorphic patterns. I was watching a video on polymorphism the other day, and the guy giving the lecture said that if at all possible, you should get rid of if statements in your code, and that a switch is almost always a sign that polymorphism is needed. At this point I was quite inspired and immediately went off to try out these new concepts, so I decided to make a small caching module using a factory method. Of course the very first thing I have to do is create a switch to decide what file encoding to choose. DANG! class Main { public static function methodA($parameter='') { switch ($parameter) { case 'a': $object = new \name\space\object1(); break; case 'b': $object = new \name\space\object2(); break; case 'c': $object = new \name\space\object3(); break; default: $object = new \name\space\object1(); } return (sekretInterface $object); } } At this point I'm not really sure what to do. As far as I can tell, I either have to use a different pattern and have separate methods for each object instance, or accept that a switch is necessary to "switch" between them. What do you guys think?

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  • Symfony2 Setting a default choice field selection

    - by Mat
    I am creating a form in the following manner: $form = $this->createFormBuilder($breed) ->add('species', 'entity', array( 'class' => 'BFPEduBundle:Item', 'property' => 'name', 'query_builder' => function(ItemRepository $er){ return $er->createQueryBuilder('i') ->where("i.type = 'species'") ->orderBy('i.name', 'ASC'); })) ->add('breed', 'text', array('required'=>true)) ->add('size', 'textarea', array('required' => false)) ->getForm() How can I set a default value for the species listbox? Thank you for your response, I apologise, I think I should rephrase my question. Once I have a value that I retrieve from the model, how do I set that value as SELECTED="yes" for the corresponding value in the species choice list? So, that select option output from the TWIG view would appear like so: <option value="174" selected="yes">Dog</option>

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  • Should concrete classes avoid calling other concrete classes, except for data objects?

    - by Kazark
    In Appendix A to The Art of Unit Testing, Roy Osherove, speaking about ways to write testable code from the start, says, An abstract class shouldn't call concrete classes, and concerete classes shouldn't call concrete classes either, unless they're data objects (objects holding data, with no behavior). (259) The first half of the sentence is simply Dependency Inversion from SOLID. The second half seems rather extreme to me. That means that every time I'm going to write a class that isn't a simple data structure, which is most classes, I should write an interface or abstract class first, right? Is it really worthwhile to go that far in defining abstract classes an interfaces? Can anyone explain why in more detail, or refute it in spite of its benefit for testability?

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  • Understanding the levels of computing

    - by RParadox
    Sorry, for my confused question. I'm looking for some pointers. Up to now I have been working mostly with Java and Python on the application layer and I have only a vague understanding of operating systems and hardware. I want to understand much more about the lower levels of computing, but it gets really overwhelming somehow. At university I took a class about microprogramming, i.e. how processors get hard-wired to implement the ASM codes. Up to now I always thought I wouldn't get more done if learned more about the "low level". One question I have is: how is it even possible that hardware gets hidden almost completely from the developer? Is it accurate to say that the operating system is a software layer for the hardware? One small example: in programming I have never come across the need to understand what L2 or L3 Cache is. For the typical business application environment one almost never needs to understand assembler and the lower levels of computing, because nowadays there is a technology stack for almost anything. I guess the whole point of these lower levels is to provide an interface to higher levels. On the other hand I wonder how much influence the lower levels can have, for example this whole graphics computing thing. So, on the other hand, there is this theoretical computer science branch, which works on abstract computing models. However, I also rarely encountered situations, where I found it helpful thinking in the categories of complexity models, proof verification, etc. I sort of know, that there is a complexity class called NP, and that they are kind of impossible to solve for a big number of N. What I'm missing is a reference for a framework to think about these things. It seems to me, that there all kinds of different camps, who rarely interact. The last few weeks I have been reading about security issues. Here somehow, much of the different layers come together. Attacks and exploits almost always occur on the lower level, so in this case it is necessary to learn about the details of the OSI layers, the inner workings of an OS, etc.

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  • Designing communications for extensibility

    - by Thomas S.
    I am working on the design stages of an application that will a) collect data from various sources (in my case that's scientific data from serial ports), keeping track of the age of the data, b) generate real-time statistics (e.g. running averages) c) display, record, and otherwise handle the data (and statistics). I anticipate that I will be adding both data producers and consumers over time, and would like to design this application abstractly so that I will be able to trivially add functionality with a small amount of interface code. What I'm stumbling on is deciding what communication infrastructure I should use to handle the interfaces. In particular, how should I make the processed data and statistics available to multiple consumers? Some things I've considered: Writing to several named pipes (variable number). Each consumer reads from one of them. Using FUSE to make a userspace filesystem where a read() returns the latest line of data even if another process has already read it. Making a TCP server, and having consumers connect and request data individually. Simply writing the consumers as part of the same program that aggregates the data. So I would like to hear your all's advice on deciding how to interface these functions in the best way to keep them separate and allow room for extenstions.

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  • Why does this article state that graduate education liberate one from concerns like the efficiency of hardware-based integers?

    - by kadaj
    Quoting The Evolution of Haskell Programmer, graduate education tends to liberate one from petty concerns about, e.g., the efficiency of hardware-based integers What exactly does this suggest? Is it that after graduation, one gets more interested in abstract ideas so much that he does not think hardware is relevant? Or that hardware is also abstracted and one is more interested in algorithms? I am trying to understand on what grounds the sentence is based.

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  • Saving a Django form to a csv file

    - by Oli
    I have a Django form that is working fine. I'd like to save the data it submits to a CSV file. Is there a "best practice" way to do this? I need to include blank fields in the CSV file where the user has not filled in a "required=False" field

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  • I have data that sends in "bursts" of 100 records with a significant delay. How do I structure my classes for multithreading?

    - by makerofthings7
    My datasource sends information in 100 batches of 100 records with a delay of 1 to 3 seconds between batches. I would like to start processing data as soon as it's received, but I'm not sure how to best approach this. Some ideas I've been playing with include: yield Concurrent Dictionary ConcurrentDictionary with INotifyProperyChanged Events etc. As you can see I'm all over the place, and would appreciate some tested guidance on how to approach this

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  • Closing a form and then call another one.

    - by elvispt
    Hi. I want to close the current form I'm on (MainForm) and then opening a second one (Form). I've tried: private void buttonStartQuiz_Click(object sender, EventArgs e) { this.Close(); Form2 form2 = new Form2(); form2.ShowDialog(); } Or adding the this.Close(); after the ShowDialog also doesn't work. Any hints? Thank you.

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  • How to learn ASP.NET MVC without learning ASP.NET Web forms

    - by Naif
    First of all, I am not a web developer but I can say that I understand in general the difference between PHP, ASP.NET, etc. I have played a little with ASP.NET and C# as well, however, I didn't continue the learning path. Now I'd like to learn ASP.NET MVC but there is no a book for a beginner in ASP.NET MVC so I had a look at the tutorials but it seems that I need to learn C# first and SQL Server and HTML, am I right? So please tell me how can I learn ASP.NET MVC directly (I mean without learning ASP.NET Web forms). What do I need to learn (You can assume that I am an absolute beginner). Update: It is true that i can find ASP.NET MVC tutorial that explain ASP.NET MVC, but I used to find ASP.NET web forms books that explain SQL and C# at the same time and take you step by step. In ASP.NET MVC I don't know how can I start! How can I learn SQL in its own and C# in its own and then combine them with ASP.NET MVC!

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