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  • Rails - undefined method `name' for nil:NilClass

    - by sscirrus
    Hi guys, Quick question. Here is my code: #routes map.resources :customers, :has_many => [:addresses, :matchings] map.connect ":controller/:action/:id" #url path: http://127.0.0.1:3000/customers/index/3 #customers controller def index @customer = Customer.find(params[:id]) end #customers view/index.html.erb ... <%= @customer.name %> ... Error: undefined method `name' for nil:NilClass. Here's my reasoning. The parameter :id is coming from my url path (i.e. we're looking for customer #3 in the above path). @customer should find that array easily, then @customer.name should produce the name, but apparently @customer is blank. Why? I assume the problem is that I'm not producing an array in my controller?

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  • An old flaw in X Window System. How does it work?

    - by Legend
    I was going through an article today when it mentioned the following: "We've found many errors over the years. One of the absolute best was the following in the X Window System: if(getuid() != 0 && geteuid == 0) { ErrorF("Only root"); exit(1); } It allowed any local user to get root access. (The tautological check geteuid == 0 was intended to be geteuid() == 0. In its current form, it compress the address of geteuid to 0; given that the function exists, its address is never 0)." The article explained what was wrong with the code but I would like to know what it means to say that "It allowed any local user to get root access". I am not an expert in C but can someone give me an exact context in which this exploit would work? Specifically, what I mean is, lets say I am the local user, how would I get root access if we assume this code to be present somewhere?

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  • Get SEO friendly URLS with Rails without method_missing?

    - by tesmar
    Hi all, Currently we are using method_missing to catch for calls to SEO friendly actions in our controllers rather than creating actions for every conceivable value for a variable. What we want are URLS like this: /students/BobSmith and NOT /students/show/342 IS there a cleaner solution than method_missing? Thank you!

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  • fastest method for minimum of two numbers

    - by user85030
    I was going through mit's opencourseware related to performance engineering. The quickest method (requiring least number of clock cycles) for finding the minimum of two numbers(say x and y) is stated as: min= y^((x^y) & -(x<y)) The output of the expression x < y can be 0 or 1 (assuming C is being used) which then changes to -0 or -1. I understand that xor can be used to swap two numbers. Questions: 1. How is -0 different from 0 and -1 in terms of binary? 2. How is that result used with the and operator to get the minimum? Thanks in advance.

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  • Indexing a method return (depending on Internationalization)

    - by Hedde
    Consider a django model with an IntegerField with some choices, e.g. COLORS = ( (0, _(u"Blue"), (1, _(u"Red"), (2, _(u"Yellow"), ) class Foo(models.Model): # ...other fields... color = models.PositiveIntegerField(choices=COLOR, verbose_name=_(u"color")) My current (haystack) index: class FooIndex(SearchIndex): text = CharField(document=True, use_template=True) color = CharField(model_attr='color') def prepare_color(self, obj): return obj.get_color_display() site.register(Product, ProductIndex) This obviously only works for keyword "yellow", but not for any (available) translations. Question: What's would be a good way to solve this problem? (indexing method returns based on the active language) What I have tried: I created a function that runs a loop over every available language (from settings) appending any translation to a list, evaluating this against the query, pre search. If any colors are matched it converts them backwards into their numeric representation to evaluate against obj.color, but this feels wrong.

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  • Catching exception in Main() method

    - by Corvin
    Consider the following simple application: a windows form created by a "new C# windows application" sequence in VS that was modified in a following way: public static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); try { Application.Run(new Form1()); } catch (Exception ex) { MessageBox.Show("An unexpected exception was caught."); } } Form1.cs contains the following modifications: private void Form1_Load(object sender, EventArgs e) { throw new Exception("Error"); } If I press F5 in IDE, then, as I expect, I see a message box saying that exception was caught and the application quits. If I go to Debug(or Release)/bin and launch the executable, I see the standard "Unhandled exception" window, meaning that my exception handler doesn't work. Obviously, that has something to do with exception being thrown from a different thread that Application.Run is called from. But the question remains - why the behavior differs depending on whether the application has been run from IDE or from command line? What is the best practice to ensure that no exceptions remain unhandled in the application?

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  • jQuery Scrollable Dynamic

    - by Coron3r
    Hi, I am doing a site where I need to change dynamically the amount of items in one slide depending on the resolution. I'm using the Jquery Tools scrollable For better understanding, here is the basic markup <div class="scrollable"> <!-- root element for the items --> <div class="items"> <!-- 1-5 --> <div> <img src="http://farm1.static.flickr.com/143/321464099_a7cfcb95cf_t.jpg" /> <img src="http://farm4.static.flickr.com/3089/2796719087_c3ee89a730_t.jpg" /> <img src="http://farm1.static.flickr.com/79/244441862_08ec9b6b49_t.jpg" /> <img src="http://farm1.static.flickr.com/28/66523124_b468cf4978_t.jpg" /> <img src="http://farm1.static.flickr.com/164/399223606_b875ddf797_t.jpg" /> </div> <!-- 5-10 --> <div> <img src="http://farm1.static.flickr.com/163/399223609_db47d35b7c_t.jpg" /> <img src="http://farm1.static.flickr.com/135/321464104_c010dbf34c_t.jpg" /> <img src="http://farm1.static.flickr.com/40/117346184_9760f3aabc_t.jpg" /> <img src="http://farm1.static.flickr.com/153/399232237_6928a527c1_t.jpg" /> <img src="http://farm1.static.flickr.com/50/117346182_1fded507fa_t.jpg" /> </div> <!-- 10-15 --> <div> <img src="http://farm4.static.flickr.com/3629/3323896446_3b87a8bf75_t.jpg" /> <img src="http://farm4.static.flickr.com/3023/3323897466_e61624f6de_t.jpg" /> <img src="http://farm4.static.flickr.com/3650/3323058611_d35c894fab_t.jpg" /> <img src="http://farm4.static.flickr.com/3635/3323893254_3183671257_t.jpg" /> <img src="http://farm4.static.flickr.com/3624/3323893148_8318838fbd_t.jpg" /> </div> </div> </div> Ok and now I would like to set, that if I have a resolution bellow 1440, I would show only e.g. 3 images <div class="scrollable"> <!-- root element for the items --> <div class="items"> <!-- 1-3 --> <div> <img src="http://farm1.static.flickr.com/143/321464099_a7cfcb95cf_t.jpg" /> <img src="http://farm4.static.flickr.com/3089/2796719087_c3ee89a730_t.jpg" /> <img src="http://farm1.static.flickr.com/79/244441862_08ec9b6b49_t.jpg" /> </div> <!-- 3-6 --> <div> <img src="http://farm1.static.flickr.com/163/399223609_db47d35b7c_t.jpg" /> <img src="http://farm1.static.flickr.com/135/321464104_c010dbf34c_t.jpg" /> <img src="http://farm1.static.flickr.com/40/117346184_9760f3aabc_t.jpg" /> </div> ..etc </div> </div> I know that I should use the screen.width(); function but how to slice and parse it depending on the resolution? Thanks for your comments!

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  • Is the scope of what Xcode's "Build and Analyze" will catch as a leak supposed to be this limited?

    - by Ranking Stackingblocks
    It doesn't care about this: NSString* leaker() { return [[NSString alloc] init]; } I thought it would have been smart enough to check if any code paths could call that function without releasing its return value (I wouldn't normally code this way, I'm just testing the analyzer). It reports this as a leak: NSString* leaker() { NSString* s = [[NSString alloc] init]; [s retain]; return s; } but NOT this: NSString* leaker() { NSString* s = [[NSString alloc] init]; // [s retain]; return s; } which seems particularly weak to me. Does it only analyze within the local scope? If the tool can't pick up on things like this, how can I expect it to pick up on actual mistakes that I might make?

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  • How to customize the to_json method in rails3?

    - by lashleigh
    I want to convert an array of Place objects to json, I've been doing it like this: var places = <%= @places.to_json.html_safe %>; The only problem is that every place in the @places array has an associated tag list that doesn't get included. I'm using the acts_as_taggable_on gem to handle tags, so to get the tag list for a place I need to say place.tag_list. What do I have to do to get the tag_list included for each place in the javascript array? I think I'll need to write my own to_json method but I don't know how. Thanks

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  • Make sure bad patterns don't come back after refactoring

    - by Let_Me_Be
    I'm refactoring an old C code. The code has absolutely no layered architecture (everything is being accessed by everything) and I'm trying to change that. I would like to cut direct access to structure members (at least write for now) and only allow access through access functions. Is there some tool (or perhaps directly the compiler) that could check this rule for me? I need this since I'm maintaining a fork and the upstream isn't very concerned with code quality.

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  • Refactoring method that was previously injected with implement

    - by ryber
    Greetings, I'm trying to override or extend the Element.show() and .hide() methods in mootools in order to add some WAI-Aria toggling. I was trying to use the Class.Refactor() method like this: Element = Class.refactor(Element, { show: function(displayString) { result = this.previous(displayString); // Do my thing return result; }, hide: function() { result = this.previous(); // Do my thing return result; } }); however, this is not working, previous is null and I think the reason is that Mootools injects those methods through Element.implement. So the methods are not native? I have figured out how to completely replace .show and .hide but I would like to retain all of their existing functionality and just add to it. Any ideas?

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  • Code Analysis Warning CA1004 with generic method

    - by Vaccano
    I have the following generic method: // Load an object from the disk public static T DeserializeObject<T>(String filename) where T : class { XmlSerializer xmlSerializer = new XmlSerializer(typeof(T)); try { TextReader textReader = new StreamReader(filename); var result = (T)xmlSerializer.Deserialize(textReader); textReader.Close(); return result; } catch (FileNotFoundException) { } return null; } When I compile I get the following warning: CA1004 : Microsoft.Design : Consider a design where 'MiscHelpers.DeserializeObject(string)' doesn't require explicit type parameter 'T' in any call to it. I have considered this and I don't know a way to do what it requests with out limiting the types that can be deserialized. I freely admit that I might be missing an easy way to fix this. But if I am not, then is my only recourse to suppress this warning? I have a clean project with no warnings or messages. I would like to keep it that way. I guess I am asking "why this is a warning?" At best this seems like it should be a message. And even that seems a bit much. Either it can or it can't be fixed. If it can't then you are just stuck with the warning with no recourse but suppressing it. Am I wrong?

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  • Execute a method less times possible - PHP

    - by serhio
    I have a site in multiple languages. I have a method that returns me the today currencies in a array. I display that currencies in a table then. // --- en/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); // --- fr/index.php <?php include_once "../exchangeRates.php"; $currencies = ReadExchangeRates(); ... // somewhere in the page <td><?php echo $currencies["eur"]["today"]; ?></td> So, every time I load, en/ or fr/ or other language, I request the exchange rates from a external site. Can I optimize this behavior (reading once per day or session)? maybe to store a global variable and check the update date?

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  • What would be my best MySQL Synchronization method?

    - by Kerry
    We're moving a social media service to be on separate data centers with global load balancing, as our other hosting provider's entire data center went down. Twice. This means that both websites need to be synchronized in some sense -- I'm less worried about the code of the pages, that's easy enough to sync, but they need to have the same database data. From my research on SO, it seems MySQL Replication is a good option, but the MySQL manual, for scaling out, says that its best when there are far more reads then there are writes/updates: http://dev.mysql.com/doc/refman/5.0/en/replication-solutions-scaleout.html In our case, it's about equal. We're getting around 200-300 thousand requests a day right now, and we can grow rapidly. Every request is both a read and write request. What would be the best method or tool to handle this?

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  • Adding a method to a function object at runtime

    - by Carson Myers
    I read a question earlier asking if there was a times method in Python, that would allow a function to be called n times in a row. Everyone suggested for _ in range(n): foo() but I wanted to try and code a different solution using a function decorator. Here's what I have: def times(self, n, *args, **kwargs): for _ in range(n): self.__call__(*args, **kwargs) import new def repeatable(func): func.times = new.instancemethod(times, func, func.__class__) @repeatable def threeArgs(one, two, three): print one, two, three threeArgs.times(7, "one", two="rawr", three="foo") When I run the program, I get the following exception: Traceback (most recent call last): File "", line 244, in run_nodebug File "C:\py\repeatable.py", line 24, in threeArgs.times(7, "one", two="rawr", three="foo") AttributeError: 'NoneType' object has no attribute 'times' So I suppose the decorator didn't work? How can I fix this?

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  • Make sure base method gets called in C#

    - by Fnatte
    Can I somehow force a derived class to always call the overridden methods base? public class BaseClass { public virtual void Update() { if(condition) { throw new Exception("..."); // Prevent derived method to be called } } } And then in a derived class : public override void Update() { base.Update(); // Forced call // Do any work } I've searched and found a suggestion to use a non-virtual Update() but also a protected virtual UpdateEx(). It just doesn't feel very neat, isn't there any better way? I hope you get the question and I am sorry for any bad English.

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  • How to call object's method from constructor?

    - by Kirzilla
    Hello, var Dog = function(name) { this.name = name; this.sayName(); } Dog.prototype.sayName = function() { alert(this.name); } I'm creating new instance of Dog object, but method sayName() is undefined. Why? Or maybe I should do something like (but I can't see difference)... var Dog = function(name) { this.name = name; this.prototype.sayName = function() { alert(this.name); } } Thank you.

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  • I'd want a method to be called only by objects of a specific class

    - by mp
    Suppose you have this class: public class A { private int number; public setNumber(int n){ number = n; } } I'd like the method setNumber could be called only by objects of a specific class. Does it make sense? I know it is not possible, is it? Which are the design alternatives? Some well known design pattern? Sorry for the silly question, but I'm a bit rusty in OO design.

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  • How to Execute Base Class's Method Before Implementors's Method?

    - by DaveDev
    I have the following page public partial class GenericOfflineCommentary : OfflineFactsheetBase { } where OfflineFactsheetBase is defined as public class OfflineFactsheetBase : System.Web.UI.Page { public OfflineFactsheetBase() { this.Load += new EventHandler(this.Page_Load); this.PreInit += new EventHandler(this.Page_PreInit); } protected void Page_PreInit(object sender, EventArgs e) { if (Request.QueryString["data"] != null) { this.PageData = StringCompressor.DecompressString(Request.QueryString["data"]); this.ExtractPageData(); } } } OfflineFactsheetBase has the following virtual method: public virtual void ExtractPageData() { // get stuff relevant to all pages that impmement OfflineFactsheetBase } which is implemented in all pages that impmement OfflineFactsheetBase as follows: public partial class GenericOfflineCommentary : OfflineFactsheetBase { public override void ExtractPageData() { // get stuff relevant to an OfflineCommentary page. } } Currently, only GenericOfflineCommentary's ExtractPageData() is firing. How can I modify this to first run OfflineFactsheetBase's ExtractPageData() and then GenericOfflineCommentary's? edit: I'm trying to avoid having to call base.ExtractPageData() in every implementor. Is this possible?

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  • How to update a vector in method

    - by gurpinars
    I'm new to C++ and trying to understand vectors. My goal is to update a vector in method: #include <vector> #include <iostream> using namespace std; void test(vector<int>& array){ for(int i=0;i<10;i++){ array.push_back(i); } } int main(){ // some integer value vector<int> array(10); test(array); for(int i=0;i<array.size();++i) cout<<array.at(i)<<endl; cout<<"array size:"<<array.size()<<endl; return 0; } output: 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 array size:20 I haven't figure out why 10 zeros add vector at first?

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  • Instantiating Java object with a passed in method

    - by superluminary
    It's been a few years since I've been heavily into Java. Coming back to it I'm seeing this pattern all over the place: ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) { // do work } }); This looks more like Functional programming to me. It's a nice pattern but how is it possible to pass a method like this? In the old days a class was a class, and once compiled there was little you could do to it. My questions are: Can anyone let me know what this pattern is called? How can I write a class that can be instantiated in this way. Are there any other useful examples of functional patterns that have made their way into Java? What do I need to Google to read more about this? Thanks.

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  • .NET "Timer" would block other method calls?

    - by Ricky
    Hi guys: In ASP.NET 3.5, we suspect a delegate triggering by a "Timer" will block other method calls. From logs, some function calls will wait for the finishing of the delegate and continue to work. Is it true? If yes, what workaround can I do? PS: The delegate contains codes to use WCF to retrieve data and the following code private void Replace<T>(ref IList<T> src, IList<T> des) { lock(src) { while (src.Count > 0) { GC.SuppressFinalize(src.ElementAt(0)); src.RemoveAt(0); } GC.SuppressFinalize(src); src = des; } } Thanks a lot.

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