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  • Passing params in rails... Breakthrough in understanding params, aka, the "aha" moment

    - by Brian McDonough
    I have a simple has_many belongs_to relationship and I want to include the parent object for the view of the belongs_to model and I have had some success, but I want it to work better. class Submission < ActiveRecord::Base belongs_to :user belongs_to :contest end class Contest < ActiveRecord::Base belongs_to :user has_many :submissions, :dependent => :destroy end In the case that works, I pass contest_id to submissions by placing it in the url: <%= link_to 'Submit Contest Entry', new_submission_path(:contest_id => @contest.id), :class => 'btn btn-primary btn-large mleft10' %> So that, combined with a hidden_field: <%= f.hidden_field :contest_id %> And a find_contest method in the controller (called with a before_filter): def find_contest #the next line is giving the error (line 76) @contest = Contest.find(params[:submission][:contest_id]) end Makes it work for submissions/new, but how do I add a find to the controller that just works across more than that one page, like if I want to access in show and index. Right now, I get an error: Started GET "/submissions?contest_id=5" for 127.0.0.1 at 2012-12-01 16:01:45 -0800 Processing by SubmissionsController#index as HTML Parameters: {"contest_id"=>"5"} User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2 ORDER BY users.created_at DESC LIMIT 1 Completed 500 Internal Server Error in 37ms NoMethodError (undefined method `[]' for nil:NilClass): app/controllers/submissions_controller.rb:76:in `find_contest' [edited] Adding show action for submissions: before_filter :find_contest, :except => [:index, :show, :edit, :update, :destroy] def find_contest @contest = Contest.find(params[:submission][:contest_id]) end def show contest_id = @submission.contest_id @submission = @commentable = Submission.find(params[:id]) @comments = @commentable.comments.order(:created_at).reverse respond_to do |format| format.html # show.html.erb format.json { render :json => @submission } end end

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  • Understanding how software testing works and what to test.

    - by RHaguiuda
    Intro: I've seen lots of topics here on SO about software testing and other terms I don't understand. Problem: As a beginner developer I, unfortunately, have no idea how software testing works, not even how to test a simple function. This is a shame, but thats the truth. I also hope this question can help others beginners developers too. Question: Can you help me to understand this subject a little bit more? Maybe some questions to start would help: When I develop a function, how should I test it? For example: when working with a sum function, should I test every input value possible or just some limits? How about testing functions with strings as parameters? In a big program, do I have to test every single piece of code of it? When you guys program do you test every code written? How automated test works and how can I try one? How tools for automated testing works and what they do? I`ve heard about unit testing. Can I have a brief explanation on this? What is a testing framework? If possible please post some code with examples to clarify the ideas. Any help on this topic is very welcome! Thanks.

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  • I need help understanding what Exercise 5-12 is asking for in the C Programming Language book.

    - by marsol0x
    K&R C Programming Language: pg. 105 Extend entab and detab to accept the shorthand entab -m +n to mean tab stops every n columns, starting at column m. entab replaces a number of spaces with a tab character and detab does the opposite. The question I have concerns the tab stops and entab. I figure that for detab it's pretty easy to determine the number of spaces needed to reach the next tab stop, so no worries there. With entab, replacing spaces with tabs is slightly more difficult since I cannot for sure know how large the tab character goes to its own tab stop (unless there is a way to know for sure). Am I even thinking about this thing properly?

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  • Understanding REST: is GET fundamentally incompatible with any "number of views" counter?

    - by cocotwo
    I'm trying to understand REST. Under REST a GET must not trigger something transactional on the server (this is a definition everybody agrees upon, it is fundamental to REST). So imagine you've got a website like stackoverflow.com (I say like so if I got the underlying details of SO wrong it doesn't change anything to my question), where everytime someone reads a question, using a GET, there's also some display showing "This question has been read 256 times". Now someone else reads that question. The counter now is at 257. The GET is transactional because the number of views got incremented and is now incremented again. The "number of views" is incremented in the DB, there's no arguing about that (for example on SO the number of time any question has been viewed is always displayed). So, is a REST GET fundamentally incompatible with any kind of "number of views" like functionality in a website? So should it want to be "RESTFUL", should the SO main page either stop display plain HTML links that are accessed using GETs or stop displaying the "this question has been viewed x times"? Because incrementing a counter in a DB is transactional and hence "unrestful"? EDIT just so that people Googling this can get some pointers: From http://www.xfront.com/REST-Web-Services.html : 4. All resources accessible via HTTP GET should be side-effect free. That is, the request should just return a representation of the resource. Invoking the resource should not result in modifying the resource. Now to me if the representation contains the "number of views", it is part of the resource [and in SO the "number of views" a question has is a very important information] and accessing it definitely modifies the resource. This is in sharp contrast with, say, a true RESTFUL HTTP GET like the one you can make on an Amazon S3 resource, where your GET is guaranteed not to modify the resource you get back. But then I'm still very confused.

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  • Best (Java) book for understanding 'under the bonnet' for programming?

    - by Ben
    What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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  • Understanding Eager Loading & How to use it? (specific issue)

    - by Elliot
    I have the following relation in my rails app: genre - has many - authors authors - belong to genre and has many books books - belongs to authors and belongs to users (users can add books to the db) in my controller I have: @books=current_user.books(:include => [:author => :genre], :order => 'books.created_at DESC')--- -- In my controller I used to have: @authors = Author.All @genres = Genre.All etc. -- In my view I have @genres.each do |genre| @authors.each do |author| if author.genre_id == genre.id stuff end end end Now that I'm using eager loading, I can't imagine this is the best way to do this (nor does it work as I don't have the @ variables) - I was wondering if anyone could shed some light on how to approach this?

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  • Asp.net tips and tricks

    - by ybbest
    Asp.net tips and tricks Here is a summary of articles I found very useful over the years while I am working on asp.net TRULY Understanding View state http://weblogs.asp.net/infinitiesloop/archive/2006/08/03/Truly-Understanding-Viewstate.aspx TRULY Understanding Dynamic Controls http://weblogs.asp.net/infinitiesloop/archive/2006/08/25/TRULY-Understanding-Dynamic-Controls-_2800_Part-1_2900_.aspx ASP.Net 2.0 – Master Pages: Tips, Tricks, and Traps http://odetocode.com/articles/450.aspx ASP.NET Tip – Use The Label Control Correctly http://haacked.com/archive/2007/02/15/asp.net_tip_-_use_the_label_control_correctly.aspx Asp.net httphandlers http://www.michaelflanakin.com/Articles/NET/NET1x/ImplementingHTTPHandlers/tabid/173/Default.aspx http://support.microsoft.com/default.aspx?scid=kb;EN-US;308001 http://msdn.microsoft.com/en-us/library/ms972974.aspx Asp.net ajax http://encosia.com/ ASP.NET 2.0 Tips, Tricks, Recipes and Gotchas http://weblogs.asp.net/scottgu/pages/ASP.NET-2.0-Tips_2C00_-Tricks_2C00_-Recipes-and-Gotchas.aspx Mastering Page-UserControl Communication http://www.codeproject.com/KB/user-controls/Page_UserControl.aspx Comparing Web Site Projects and Web Application Projects Web Deployment Projects .NET Radio Show http://www.dotnetrocks.com/ Herdingcode http://herdingcode.com/ Clean Code talk http://www.objectmentor.com/videos/video_index.html .NET Video Show http://www.dnrtv.com/ .Net User group http://chicagoalt.net/home http://exposureroom.com/members/RIAViewMirror.aspx/assets/ FAQ Why should you remove unnecessary C# using directives? http://stackoverflow.com/questions/136278/why-should-you-remove-unnecessary-c-using-directives http://stackoverflow.com/questions/2009471/what-is-the-benefit-of-removing-redundant-imports-in-vb-net-or-using-in-c-file http://codeclimber.net.nz/archive/2009/12/30/best-of-2009-the-5-most-popular-posts.aspx

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  • How important is Domain knowledge vs. Technical knowledge?

    - by Mayank
    I am working on a Trading and Risk Management application and although from a C# background, I have been asked to work on SSIS packages. Now I can live with that. The pain point is that there is too much emphasis on business understanding. Trading (Energy Trading to be exact) is a HUGE area and understanding every little bit of it is overwhelming. But for the past two months I have been working on understanding the business terms - Mark To Market, Risk Metrics, Positions, PnL, Greeks, Instruments, Book Structure... every little detail (you get the point). Now IMHO, this is the job of a BA. Sure it is very important for developers to understand the business but where do you draw the line? When I talked to my manager about this, he almost mocked me by saying that anybody can learn a technology in a week. It's the business that's harder. My long term aspiration is to remain on the technical side, probably become an architect (if possible). If I wanted to focus so much on business I would have pursued an MBA! I want to know if I am wrong or too naive in understanding the business importance or is my frustration justified?

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  • JavaCC: How can one exclude a string from a token? (A.k.a. understanding token ambiguity.)

    - by java.is.for.desktop
    Hello, everyone! I had already many problems with understanding, how ambiguous tokens can be handled elegantly (or somehow at all) in JavaCC. Let's take this example: I want to parse XML processing instruction. The format is: "<?" <target> <data> "?>": target is an XML name, data can be anything except ?>, because it's the closing tag. So, lets define this in JavaCC: (I use lexical states, in this case DEFAULT and PROC_INST) TOKEN : <#NAME : (very-long-definition-from-xml-1.1-goes-here) > TOKEN : <WSS : (" " | "\t")+ > // WSS = whitespaces <DEFAULT> TOKEN : {<PI_START : "<?" > : PROC_INST} <PROC_INST> TOKEN : {<PI_TARGET : <NAME> >} <PROC_INST> TOKEN : {<PI_DATA : ~[] >} // accept everything <PROC_INST> TOKEN : {<PI_END : "?>" > : DEFAULT} Now the part which recognizes processing instructions: void PROC_INSTR() : {} { ( <PI_START> (t=<PI_TARGET>){System.out.println("target: " + t.image);} <WSS> (t=<PI_DATA>){System.out.println("data: " + t.image);} <PI_END> ) {} } Let's test it with <?mytarget here-goes-some-data?>: The target is recognized: "target: mytarget". But now I get my favorite JavaCC parsing error: !! procinstparser.ParseException: Encountered "" at line 1, column 15. !! Was expecting one of: !! Encountered nothing? Was expecting nothing? Or what? Thank you, JavaCC! I know, that I could use the MORE keyword of JavaCC, but this would give me the whole processing instruction as one token, so I'd had to parse/tokenize it further by myself. Why should I do that? Am I writing a parser that does not parse? The problem is (i guess): hence <PI_DATA> recognizes "everything", my definition is wrong. I should tell JavaCC to recognize "everything except ?>" as processing instruction data. But how can it be done? NOTE: I can only exclude single characters using ~["a"|"b"|"c"], I can't exclude strings such as ~["abc"] or ~["?>"]. Another great anti-feature of JavaCC. Thank you.

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  • How to understand Linux kernel source code for a beginner?

    - by Amit Chavan
    Hi, I am a student interested in working on Memory Management, particularly the page replacement component of the linux kernel. What are the different guides that can help me to begin understanding the kernel source? I have tried to read the book Understanding the Linux Virutal Memory Manager by Mel Gorman and Understanding the Linux Kernel by Cesati and Bovet, but they do not explain the flow of control through the code. They only end up explaining various data structures used and the work various functions perform. This makes the code more confusing. My project deals with tweaking the page replacement algorithm in a mainstream kernel and analyse its performance for a set of workloads. Is there a flavor of the linux kernel that would be easier to understand(if not the linux-2.6.xx kernel)?

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  • I want to master ASP.NET - What concepts should I focus on/What concepts do you most value?

    - by Josh
    I start a job this summer doing work in ASP.NET 4 (C#). I plan on working with some legacy code as well as MVC. I want to get a running start. I have good understanding of HTML/CSS/Javascript, and pretty good understanding of C# itself, Design principles, Design Patterns, and understand masterpages, basic MVC2, and code behinds for web forms. In your opinion what aspects of ASP.NET are the most important to master for web applications? What do you value most in your usage of ASP.NET? Do you have a recommendation for understanding the internals of ASP.NET itself?

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  • How to understand Linux kernel source code for a beginner?

    - by user16867
    I am a student interested in working on Memory Management, particularly the page replacement component of the linux kernel. What are the different guides that can help me to begin understanding the kernel source? I have tried to read the book Understanding the Linux Virutal Memory Manager by Mel Gorman and Understanding the Linux Kernel by Cesati and Bovet, but they do not explain the flow of control through the code. They only end up explaining various data structures used and the work various functions perform. This makes the code more confusing. My project deals with tweaking the page replacement algorithm in a mainstream kernel and analyse its performance for a set of workloads. Is there a flavor of the linux kernel that would be easier to understand(if not the linux-2.6.xx kernel)?

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  • C++ function call routes resolver

    - by Poni
    Hi! I'm looking for a tool that will tell/resolve for every function all the call paths (call it "routes") to it. For example: void deeper(int *pNumber) { *pNumber++; } void gateA(int *pNumber) { deeper(pNumber); } void gateB(int *pNumber) { gateA(pNumber); } void main() { int x = 123; gateA(&x); gateB(&x); } See? I need a tool that will tell me all the routes to deeper(), and more if possible. By saying "more" I mean that it will tell me if the pointer is the same as been provided to the calling function. This will greatly save me time. Thanks!

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  • Five new junior developers and lots of complex tasks. What's now?

    - by mxe
    Our company has hired five new junior developers to help me to developer our product. Unfortunately the new features and incoming bug fixes usually require deeper knowledge than a recently graduated developer usually has (threading/concurrency, debugging performance bottlenecks in a complex system, etc.) Delegating (and planning) tasks which they (probably) can solve, answering their questions, mentoring/managing them, reviewing their code use up all of my time and I often feel that I could solve the issues less time than the whole delegating process takes (counting only my time). In addition I don't have time to solve the tasks which require deeper system knowledge/more advanced skills and it does not seem that it will change in the near future. So, what's now? What should I do to use their and my time effectively?

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  • How to loop through a javascript object and check each key exists in a separate multidimensional object

    - by Paul Atkins
    I have 2 javascript objects and I am trying to loop through one object and check whether the key exists in a second multidimensional object going one level deeper each time. Here are the two objects var check = {'scope':'instance', 'item':'body', 'property': 'background'}; var values = {'instance': {'body' : {'background': '000000'}}}; b.map(check, function(key){ console.log(values[key]); }); How am I able to check 1 level deeper in the values object each time? What I am trying to do is check the values object as follows: 1st values['instance'] 2nd values['instance']['body'] 3rd values['instance']['body']['background'] Thanks

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  • Book suggestions for GUI related topics [closed]

    - by asrijaal
    In the past, I've developed more on the server side, so no big GUI/graphic programming topics have crossed my way so far. I'm switching a little bit to the mobile plattforms (iOS, android) and would like to gather more info on the visual/graphic side. Using the SDK controls/widgets isn't that challenging and I would love to get deeper into the view/presentation layer. Animations, drawing itself, probably OpenGL. Any books that would take me a little deeper in understanding how drawing actually works would be helpful.

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  • Useful programming languages for hardware programming

    - by Sebastian Griotberg
    I am thinking to take the next semester a course called "Digital systems architecture", and I know that we need to program micro-controllers with several programming languages such as C, C++, verilog, and VHDL. I want to be prepared to take that course, but I need to know if I need to study deeper these languages. At this moment, I have taken one course in basic Java dealing with basic methods, data types, loop structures, vectors, matrices, and GUI programing. Must I study deeper Java and then go with C, and C++? Besides, I know basic verilog and VHDL.

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  • What do you need to know to be a world-class master software developer? [closed]

    - by glitch
    I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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  • Newbie questions about COM

    - by smwikipedia
    Hi, I am quite new to COM so the question may seem naive. Q1. About Windows DLL Based on my understanding, a Windows DLL can export functions, types(classes) and global variables. Is this understanding all right? Q2. About COM My naive understanding is that: a COM DLL seems to be just a new logical way to organize the functions and types exported by a standard Windows DLL. A COM DLL exports both functions such as DllRegisterServer() and DllGetClassObject(), and also the Classes which implements the IUnknown interface. Is this understanding all right? Q3. *.def & *.idl *.def is used to define the functions exported by a Windows DLL in the traditional way, such as DllGetClassObject(). *.idl is used to define the interface implemented by a COM coclass. Thanks in advance.

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  • Is there any way static block is executed more than once? if so then how?

    - by learner
    My Understanding Static block is executed during class loading, If a class is already loaded then there is no way to load the class other than class reloading Doubt/Question 1) Is there any time JVM reloads the class? My Understanding In Class Loading JVM loads source of the Java file, so it can not keep all thousands files source is a memory, it should discard the rarely used code and reload again when it is necessary and during reload JVM is not initializing static variables and locks again(may be using some tracking mechanism) Doubt/Question 2) If my above understanding is incorrect then please correct me

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  • Is there a formal definiton of software quality

    - by user970696
    I am looking for a formal definition of software quality. It is my understanding that ISO 25000 is intended to provide or measure the quality of a piece of software, but it doesn't appear ready yet and I can't tell if it specifically contains such a definiton. Currently ISO 9126 did contain one such definition, but my understanding is that it is being replaced with ISO 25000. So I ask, is there are formal definition of software quality?

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