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  • update_attributes with validations

    - by Timothy
    I have the following contrived example in Rails. I want to make sure the Garage model has at least one car with this. class Garage has_many :cars validate :at_least_one_car def at_least_one_car if cars.count == 0 errors.add_to_base("needs at least one car") end end end class Car belongs_to :garage end In my form I have a remove button that will set the hidden field _delete to true for an existing car. Let's say there is only one car object and I "delete" it in my form, if I do garage_object.update_attributes(params[:garage]), it will delete the car model and make the garage object invalid. Is there to a way to make it not update the attributes if it will make the model invalid?

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  • c++ classes & lua

    - by anon
    I want to have C++ objects that I can read/write in both C++ & Lua. I have looked at: http://www.lua.org/pil/28.html However, I do not like that solution, since my objects have constructors & destructors (and they are important as I use RAII and these take care of reference counts). What I don't like in the PIL solution is that the object is allocated in Lua's heap. What i want instead, is to create hte C++ object on my own, and just have lua have a way to do get/set on them. Does anyone have a good tutorial/link on this? Tanks!

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  • Why are Objective-C instance variables declared in an interface?

    - by Chase
    I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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  • asp.net C# variable as Image1.ImageUrl property

    - by ModS
    I would like to Click "buttonImage1" and have that store "photos/Image1.jpg" into a var called Photo. then have ButtonImage2.ImageUrl = (Photo). I am using an UpdatePanel to refresh the area with the images so the only problem is actually setting the variable correctly and then using it correctly. Reworded: how can I store a path to an image in a variable then set it correctly as a image's URL path? protected void Button2_Click(object sender, ImageClickEventArgs e) { Evt = ("~/events/ev2.jpg"); } protected void Image2_Click(object sender, ImageClickEventArgs e) { Image1.ImageUrl = (Evt); }

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  • jQuery/JSON/PHP failing

    - by user730936
    I am trying to call a php script that accepts JSON data, writes it into a file and returns simple text response using jQuery/AJAX call. jQuery code : $("input.callphp").click(function() { var url_file = myurl"; $.ajax({type : "POST", url : url_file, data : {'puzzle': 'Reset!'}, success : function(data){ alert("Success: " + data); }, error : function (data) { alert("Error: " + data); }, dataType : 'text' }); }); PHP Code : <?php $thefile = "new.json"; /* Our filename as defined earlier */ $towrite = $_POST["puzzle"]; /* What we'll write to the file */ $openedfile = fopen($thefile, "w"); fwrite($openedfile, $towrite); fclose($openedfile); echo "<br> <br>".$towrite; ?> However, the call is never a success and always gives an error with an alert "Error : [Object object]".

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  • How is a constructor executed?

    - by simion
    I am doing some reviison from the lecture slides and it says a constructor is executed in the following way; If the constructor starts with this, recursively execute the indicated constructor, then go to step 4. Invoke the explicitly or implicitly indicated superclass constructor (unless this class is java.lang.Object) Initialise the fields of the object in the order in which they were declared in this class Execute the rest of the body of this constructor. What i dont undertsand is that, a constructor can never "start" with this, because even if it forms no class heirarchy/relationship then super() is inserted by default. How would this fit in with the description above? Thanks

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  • Initializing a value through a Session variable

    - by William Calleja
    I need to Initialize a value in a Javascript by using a c# literal that makes reference to a Session Variable. I am using the following code <script type="text/javascript" language="javascript" > var myIndex = <%= !((Session["myIndex"]).Equals(null)||(Session["myIndex"]).Equals("")) ? Session["backgroundIndex"] : "1" %>; However the code above is giving me a classic Object reference not set to an instance of an object. error. Why? Shouldn't (Session["myIndex"]).Equals(null) capture this particular error?

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  • How to reference/link another project in grails workspace without using jar files?

    - by Ivan Alagenchev
    I have a Grails website that references a java core application. I have been successful in adding a .jar dependency to that project; however the java project is in the same workspace as my grails project and I would ultimately like to reference that project directly. I don't want to deal with the added step of creating a new jar file every time that there is a modification to the java project, cleaning and updating my dependencies. I added the java project to my grails' project "Java Build Path" and at first everything seemed to work fine, but when I run grailscompile, the compiler fails to resolve all imports that point to the java project. I am using Spring Source Toolsuite as my IDE.

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  • Javascript Pointers question with Dates

    - by Mega Matt
    I noticed this situation in my code (unfortunately), and was able to duplicate it in my own JS file. So I have this code: var date1 = new Date(); // today var date2 = date1; date2 = date2.setDate(date2.getDate() + 1); // what is date1? After this code executes, date1 is today's date + 1! This harkens back to my undergrad days when I learned about pointers, and I guess I'm a little rusty. Is that what's happening here? Obviously I've moved the assignment away from date1, and am only modifying date2, but date1 is being changed. Why is this the case? Incidentally, after this code executes date2 is a long number like 1272123603911. I assume this is the number of seconds in the date, but shouldn't date2 still be a Date object? setDate() should return a Date object... Thanks for the help.

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  • Returning objects with dynamic memory

    - by Caulibrot
    I'm having trouble figuring out a way to return an object (declared locally within the function) which has dynamic memory attached to it. The problem is the destructor, which runs and deletes the dynamic memory when the object goes out of scope, i.e. when I return it and want to use the data in the memory that has been deleted! I'm doing this for an overloaded addition operator. I'm trying to do something like: MyObj operator+( const MyObj& x, const MyObj& y ) { MyObj z; // code to add x and y and store in dynamic memory of z return z; } My destructor is simply: MyObj::~MyObj() { delete [] ptr; } Any suggestions would be much appreciated!

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  • How to list library dependencies of a non-native binary?

    - by lvella
    When developing for native platform, I can use ldd to list all the shared libraries (.so files) a binary executable I build will try to load upon start-up. But when cross-compiling, I don't know how to get the same information. The ldd is not a normal binutils utility, like strip or ar, that can be built alongside gcc for cross compiling, but instead, it is a cryptic shell script that apparently can only run on native platform. So, using the cross-target binutils tools, is there any way to get a list of the dynamically linked dependency for of a foreign binary?

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  • Why do C# and Java require everything to be in a class?

    - by Javier Badia
    It seemed like this question should have been asked before, but searching found nothing. I've always wondered what's the point of making us put every bit of code inside a class or interface. I seem to remember that there were some advantages to requiring a main() function like C, but nothing for classes. Languages like Python are, in a way, even more object oriented than Java since they don't have primitives, but you can put code wherever you want. Is this some sort of "misinterpretation" of OOP? After all, you can write procedural code like you would in C and put it inside a class, but it won't be object oriented.

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  • Silverlight Windows Phone 7: Load Images From URL

    - by Lennie De Villiers
    Hi, I got the code below that is trying to load an image from the web into an Image control, when I run it I get an error on the given line that no network access is allowed: private void button1_Click(object sender, RoutedEventArgs e) { WebClient webClientImgDownloader = new WebClient(); webClientImgDownloader.OpenReadCompleted += new OpenReadCompletedEventHandler(webClientImgDownloader_OpenReadCompleted); webClientImgDownloader.OpenReadAsync(new Uri("http://dilbert.com/dyn/str_strip/000000000/00000000/0000000/000000/80000/5000/100/85108/85108.strip.print.gif", UriKind.Absolute)); } void webClientImgDownloader_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { BitmapImage bitmap = new BitmapImage(); bitmap.SetSource(e.Result); // ERROR HERE! image1.Source = bitmap; } Silverlight for Windows Phone 7

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  • simple JQuery example is causing me troubles for unknown reason

    - by cerr
    I'm relatively new to JQuery and would like to try something. I just followed a simple tutorial to start up with on http://docs.jquery.com/Tutorials:Getting_Started_with_jQuery So I specified my script in the : <script type="text/javascript"> $(document).ready(function() { $("a").click(function() { alert("Hello world!"); }); }); </script> and included a test link in the : <a href="">Link</a> however, when I refresh thet document my browser keeps saying TypeError: Property '$' of object [object Window] is not a function which I can understand for "normal" JavaScript but I believe this kind of function is new in JQuery. Can someone assist mer here, please? links:http://wittmerperformance.com/site/

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  • how to access a different movieclip within the flash in AS3

    - by Pieter888
    I've been trying to learn Action Script 3 the past few weeks, making tiny interactive games to learn the basics. I stumble upon a problem every now and then but most of the times google helps me out. But this problem has got me stuck so please help: The main stage contains two objects(movieclips), the player and a wall. The player has got his own code so when I drag in the player object I don't have to write any code into the main stage to be able to move the player. This all worked pretty well and I now wanted to add the wall so the player actually has something to bounce into. Now here is the problem, I want to check if the player touches the wall, I've done this before but that was when I used the main stage as my coding playground instead of putting the code in movieclips. How can I check if the player hits the wall within the movement code of the player object?

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  • Is it a header file or library? in a makefile

    - by gccinac
    I already know the differences between a header file and a library. However, when I'm writing my makefile, I have some difficulties on deciding if I should put something as a dependency of the file or just at the linking rule. For example: I have 2 simple files: main.c: #include <stdio.h> main(){ printf("this is the sine or 90"); sinus(90); } and func.c: #include <math.h> sinus(int num){ return sin(num); } and my makefile is: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c main.o: main.c Well, my question is why this makefile works and this one doesn't: main: main.o func.o gcc main.o func.o -lm -o main func.o: func.c math.h main.o: main.c

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  • For what purposes have YOU used T4?

    - by Chris Melinn
    T4 has existed for several years in Visual Studio, but doesn't get a lot of attention. However, for those that know it, there seems to be some very creative and useful purposes. I am researching some different ways that T4 is used, and I would appreciate to hear how YOU may have used it for real life scenarios. I am primarily interested in non-standard and creative uses. Some interesting examples: Phil Haack uses T4 to create static CSS files from .less To Generate WPF and Silverlight Dependency Properties using T4 Templates Note: I realize this is a discussion-oriented question, but the answers could be helpful to others. I have tagged it as subjective and also marked as "community wiki", so please allow the question to remain open. Thanks!

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Makefile: expand dependencies

    - by Danyel
    First off, the title is very generic because there are just tons of ways of how to possibly solve this. However, I'm looking for a clean and neat way. Situation: I have two equal object files foo.o and foo-pi.o, the latter of which is position-independent (compiled with -fPIC). Both depend on foo.h and bar.h. Problem: How do I, without code duplication, declare dependency of all foo*.o to bar.h? Solutions so far: $(shell bash -c 'echo -ne foo{-pi,}.o'}: bar.h $(addsuffix .o, $(addprefix fo, o-pi o)): bar.h The first solution is not portable on systems that don't support bash, the second is a dirty solution since I could not figure out how to use empty strings in addprefix.

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  • Choose between multiple options with defined probability

    - by Sijin
    I have a scenario where I need to show a different page to a user for the same url based on a probability distribution, so for e.g. for 3 pages the distribution might be page 1 - 30% of all users page 2 - 50% of all users page 3 - 20% of all users When deciding what page to load for a given user, what technique can I use to ensure that the overall distribution matches the above? I am thinking I need a way to choose an object at "random" from a set X { x1, x2....xn } except that instead of all objects being equally likely the probability of an object being selected is defined beforehand.

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  • Accessing Controls Values Before Finishing Page_Load

    - by userk
    Hi. I'm with a problem and want to know if someone can help me. I'm creating a table with some controls and I want to save all control values in every postback. As the controls are just defined after the page_load, I can't solve my problem this way: object o; protected void Page_Load(object sender, EventArgs e) { o = createObject(); Create_Table(); if (Page.IsPostBack) Save_Data(); } I thought I could execute Save_Data() at the begining of every postback event, but I think that should exist a better way to solve my problem. Thanks.

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  • Best way to get photoshop to optimise 35 related pictures for fast transmission

    - by thenerd
    I have 35 pictures taken from a stationary camera aimed at a lightbox in which an object is placed, rotated at 10 degrees in each picture. If I cycle through the pictures quickly, the image looks like it is rotating. If I wished to 'rotate' the object in a browser but wanted to transmit as little data as possible for this, I thought it might be a good idea to split the picture into 36 pictures, where 1 picture is any background the images have in common, and 35 pictures minus the background, just showing the things that have changed. Do you think this approach will work? Is there a better route? How would I achieve this in photoshop?

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  • how can I pass method Of one class to another class ?

    - by srikanth rongali
    I have a ClassA. in ClassA there is a method(-(void)parseData:). I have a ClassB which have ClassA object. And ClassB *aClassB is member variable of ClassA. In ClassB the code is aClassB = [[ClassB alloc]init]; [aClassB parseData]; I have ClassC. I need to use the method parseData of ClassB in ClassC. I think I can use the object created in ClassB of ClassA. How can I pass the method to ClassC ? Thank You.

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  • design-pattern libraries ready-to-use?

    - by fayer
    symfony has released some of their components free to use outside the framework. i have used the event dispatcher and dependency injection...they are awesome! i wonder if there are other components/libraries (from other frameworks etc) that in the same way help you manage various design patterns? eg. decorator, facade, singleton, chain of commands etc. i think symfony is on the right path, abstracting away the design patterns. are there any other components out there doing the same? thanks

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  • Java generic function for performing calculations on integer, on double?

    - by Daniel
    Is this possible? Surely if you passed in a double, any sort of function implementation code which casts an object to an Integer would not be able to work unless the cast 'Integer' was specifically used? I have a function like: public static void increment(Object o){ Integer one = (Integer)o; system.out.println(one++); } I cant see how this could be made generic for a double? I tried public static <E> void increment(E obj){ E one = (E)o; system.out.println(one++); } but it didn't like it?

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