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  • Rails creating and updating 2 model records simultaneously

    - by LearnRails
    I have 2 tables product and history product table id name type price location 1 abc electronics $200 aisle1 history table id product_id status 1 1 price changed from $200 to $180 Whenever the product price or location is updated by a user by hitting the update button, 1) the changes should be automatically be reflected in the history status column without the user having to enter that manually. if the price is updated from 200 to 180 then a new history row will be created with new id and the status column will say ' price changed from $200 to $180' if the location is updated from aisle1 to aisle 2 then status displays ' loc changed from ailse1 to aisle 2' I tried to @product = Product.new(params[:product]) @history= History.new(params[:history]) if @product.save @history.new(attributes) == I am not sure of whether this approach is correct I would really appreciate if someone could tell me how the history can be automatically updated in this case.

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  • Obj-C: Creating an object with a String name

    - by FnGreg7
    Hey all. I know this sounds simple, but I can't find a way to do it. I have a method in Obj-C that takes in a NSString and then should create a new class with the String as its title. -(DataModel *)createDataModel:(NSString *)dataModel_name { DataModel *[initWithString:dataModel_name] = [[DataModel alloc] init]; } I know I have some problems in this. For starters, I don't know how to define a return on an object whose name could change. Second, I know this doesn't compile considering the initWithString method is wrong. I just don't know what to do or what method to use so that I can create this DataModel object with the specified name...

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  • Call function from object instantiated in one class in another

    - by Dk43
    I have two classes, both of which need to be able to call the same instance of entitymanager class Engine { EntityManager::Entitymanager EManager; } And I need to add an object to a vector contained by this particular instance of Engine. What I want to do is be able to add a bullet spawned by the player to the vector that contains all my entities. class Player : Entity { void SpawnBullet() {Engine::EManager.Add(BULLET);} } The above returns this error: error: object missing in reference to ‘Engine::EManager’ How do I resolve this? Any help or pointers in the right direction would be much appreciated!

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  • Pass C++ object to Lua function

    - by peterdemin
    Hello there. I have a C++ project, where 1 method of a 1 class changes very often. So I want to take that code from C++ to Lua. Note, I'm novice to Lua. The whole task: Bind some class methods to Lua state machine; Pass reference to class object to a function, written in Lua; Operate with passed C++ object in Lua function. I've found how to make first step with Lunar, and can't cope with second and third. I can't use SWIG and boost.

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  • Avoiding repetition with libraries that use a setup + execute model

    - by lijie
    Some libraries offer the ability to separate setup and execution, esp if the setup portion has undesirable characteristics such as unbounded latency. If the program needs to have this reflected in its structure, then it is natural to have: void setupXXX(...); // which calls the setup stuff void doXXX(...); // which calls the execute stuff The problem with this is that the structure of setupXXX and doXXX is going to be quite similar (at least textually -- control flow will prob be more complex in doXXX). Wondering if there are any ways to avoid this. Example: Let's say we're doing signal processing: filtering with a known kernel in the frequency domain. so, setupXXX and doXXX would probably be something like... void doFilter(FilterStuff *c) { for (int i = 0; i < c->N; ++i) { doFFT(c->x[i], c->fft_forward_setup, c->tmp); doMultiplyVector(c->tmp, c->filter); doFFT(c->tmp, c->fft_inverse_setup, c->x[i]); } } void setupFilter(FilterStuff *c) { setupFFT(..., &(c->fft_forward_setup)); // assign the kernel to c->filter ... setupFFT(..., &(c->fft_inverse_setup)); }

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  • Return an opaque object to the caller without violating type-safety

    - by JS Bangs
    I have a method which should return a snapshot of the current state, and another method which restores that state. public class MachineModel { public Snapshot CurrentSnapshot { get; } public void RestoreSnapshot (Snapshot saved) { /* etc */ }; } The state Snapshot class should be completely opaque to the caller--no visible methods or properties--but its properties have to be visible within the MachineModel class. I could obviously do this by downcasting, i.e. have CurrentSnapshot return an object, and have RestoreSnapshot accept an object argument which it casts back to a Snapshot. But forced casting like that makes me feel dirty. What's the best alternate design that allows me to be both type-safe and opaque?

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  • Silverlight ~ MVVM ~ Dynamic setting of Style property based on model value

    - by eponymous23
    I have a class called Question that represents a question and it's answer. I have an application that renders an ObservableCollection of Question objects. Each Question is rendered as a StackPanel that contains a TextBlock for the question verbiage, and a TextBox for the user to enter in an answer. The questions are rendered using an ItemsControl, and I have initially set the Style of the Questions's StackPanel using a StaticResource key called 'IncorrectQuestion' (defined in UserControl.Resources section of the page). In the UserControl.Resources section, I've also defined a key calld 'CorrectQuestion' which I need to somehow apply to the Question's StackPanel when the user correctly answers the question. My problem is I'm not sure how to dynamically change the Style of the StackPanel, specifically within the constraints of a ViewModel class (i.e. I don't want to put any style selection code in the View's code-behind). My Question class has an IsCorrect property which is accurately being set when the correction is answered. I'd like to somehow reflect the IsCorrect value in the form of a Style selection. How do I do that?

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  • ActionScript - Automatic containment and repositioning of object bounds

    - by TheDarkIn1978
    when adding objects arbitrarily to the stage with mouse clicks, is there a more simple way to making sure the object's bounds do not exceed those of the stage? currently i'm calling something like this before adding the object to the display list: var newSwatchRect:Rectangle = newSwatch.getBounds(this); if (newSwatchRect.x < stage.x) {newSwatchRect.x = stage.x;} if (newSwatchRect.y < stage.y) {newSwatchRect.y = stage.y;} if (newSwatchRect.x + newSwatchRect.width > stage.stageWidth) {newSwatchRect.x = stage.stageWidth - newSwatchRect.width;} if (newSwatchRect.y + newSwatchRect.height > stage.stageHeight) {newSwatchRect.y = stage.stageHeight - newSwatchRect.height;}

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  • Getting error "Activex Component cannot create Object" while using .NET dll in VB 6 Code

    - by ssman321
    HI, I am deploying a VB6 application on client machine. The Application need to access code from a C#.NET dll. I created a COM object of the .NET dll and used it VB 6 using the side by side versioning (Registration free COM). It is running fine on the development machine but on the client machine it is throwing an error "ActiveX Component cannot create Object" I created two manifest files one for the VB application and the other one for the C# application. I embedded the C# manifest file in the C#.NET dll through visual studio 2008. Am I missing some step. Please help me out. Thanks in advance.

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  • finding last loop through a jQuery object

    - by DA
    Sample jquery. Assume $cog is a cached selector of multiple items. $cog.fadeOut('slow',function(){ alert('hey'); }) In that example, of $cog is a jQuery object of 4 DOM elements, the above will fade each element out one by one, and trigger an alert each time on the callback (4 alerts). I'd like to only call the alert when all 4 elements are done with their fadeOut function. This: $cog.fadeOut('slow',function(){ }) alert('hey'); when run, will show an alert, then the $cog elements disappear (I'm guessing due to timing issues with the fadeOut animation) Is there a way when calling a function against multiple DOM objects in a jQuery object to know when it's done with the last item?

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  • About memory and delete object in c++

    - by barssala
    I will give some examples and explain. First, I declare some object like CString* param = new CString[100] And when I declare this one, my memory would increase a little bit because it's some implemented string. Then I store this object in some list of CString just like List<CString> myList = new List<CString>; // new list of CString myList.add(param); This is my question: I wanna know, when I delete myList, my param isn't deleted, right? And memory in param still exists. Do I misunderstand?

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  • Java classloader delegation model ?

    - by Tony
    When calling a loadClass() on a class loader, the class loader firstly check the class if had been loaded or directly delegate this check to it's parent class loader ? Java api says: When requested to find a class or resource, a ClassLoader instance will delegate the search for the class or resource to its parent class loader before attempting to find the class or resource itself. But there's a specific chapter about class loader in the book <java reflection in action> and says: Class loader calls findLoadedClass to check if the class has been loaded already.If a class loader does not find a loaded class, calls loadClass on the parent class loader. which is correct ?

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  • Easy way to cast an object array into another type in C#

    - by Na7coldwater
    I want to be able to be able to quickly cast an array of objects to a different type, such as String, but the following code doesn't work: String[] a = new String[2]; a[0] = "Hello"; a[1] = "World"; ArrayList b = new ArrayList(a); String[] c = (String[]) b.ToArray(); And I don't want to have to do this: String[] a = new String[2]; a[0] = "Hello"; a[1] = "World"; ArrayList b = new ArrayList(a); Object[] temp = b.ToArray(); Object[] temp = b.ToArray(); String[] c = new String[temp.Length]; for(int i=0;i<temp.Length;i++) { c[i] = (String) temp[i]; } Is there an easy way to do this without using a temporary variable?

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  • How to cast/convert form Object in an byte[] array

    - by maddash
    I've got a maybe simple problem, but at the moment I am not able to solve it. I have an Object and I need to convert it into a byte[]. public byte[] GetMapiPropertyBytes(string propIdentifier) { return (byte[])this.GetMapiProperty(propIdentifier); //InvalidCastException } Exception: Unable to cast COM object of type 'System.__ComObject' to class type 'System.Byte[]'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface. So far so good - I've tried to serialize it, but I got another exception - NOT serializable Could someone help me? I need a method to convert it...

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  • Why people define class, trait, object inside another object in Scala?

    - by Zwcat
    Ok, I'll explain why I ask this question. I begin to read Lift 2.2 source code these days. In Lift, I found that, define inner class and inner trait are very heavily used. object Menu has 2 inner traits and 4 inner classes. object Loc has 18 inner classes, 5 inner traits, 7 inner objects. There're tons of codes write like this. I wanna to know why the author write it like this. Is it because it's the author's personal taste or a powerful use of language feature?

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  • How to query a collection of inherited object for a particular object type in grails ?

    - by quilovnic
    Hi, I have a this model : class Question{ Set components static hasMany = [components: QuestionComponent] } class QuestionComponent{ static belongsTo = Question } class QuestionComponentStatus extends QuestionComponent{ } class QuestionComponentOther extends QuestionComponent{ } I want to get only QuestionComponentStatus from Set components : questionInstance.components. ? Thanks a lot

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  • passing a parameter from an other model on ruby

    - by MAGE
    I'm very newbie in ruby and need your help. I must save a "Topic" and make it like this : @topic = Topic.new(params[:topic]) But I would like to pass an other information to this topic. It has a field "community_id" that link it to a community. The logged user has this information on his table. How can I pass the "community_id" from the logged user to the "community_id" of the "topic" created ? thx for your help

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  • How to assign one object to another in Linq c# without making new

    - by LLL
    I m facing issue in assiging one object to another in linq sql. In this example Func<result, result> make = q => new result { Id = q.Id, lName = q.lName, GroupId = q.GroupId, Age = (from tags in q.age where tags.Del == null && tags.lId == q.Id select age).ToEntitySet(), }; p = (from q in dc.results where q.Id == Id.Value select make(q)).First(); i am making new and assigning the object, but i dont want to do this, it will cause propblem in insertion. so i want to assign without making new, how is it possible?

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  • javascript object creating

    - by Md. Shohel Rana
    I have a javascript object like this var student = function () { this.id = 1; this.Name = "Shohel"; this.Roll = "04115407"; this.Session = "03-04"; this.Subject = "CSE"; }; and i have a javascript array list like this var students = []; now i want to push student into students, this is shown below students.push(new student()) //no prolem students.push(new student[id = 3]) //Problem here second line occurs exceptions, how can i push javascript object like as c# add list, which is representing second line? thanks

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  • Calling a method on an object a bunch of times versus constructing an object a bunch of times

    - by Ami
    I have a List called myData and I want to apply a particular method (someFunction) to every element in the List. Is calling a method through an object's constructor slower than calling the same method many times for one particular object instantiation? In other words, is this: for(int i = 0; i < myData.Count; i++) myClass someObject = new myClass(myData[i]); slower than this: myClass someObject = new myClass(); for(int i = 0; i < myData.Count; i++) someObject.someFunction(myData[i]); ? If so, how much slower?

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  • How does one find a '.' in a string object in Object-C

    - by NaZer
    I am working on getting a simple calculator working as part of my adventure to learning Object-C and iOS development. In Object-C using NSString, how does one look for a period in a string? Based on the comments this is what I got so far. NSString * tmp = [display text]; NSLog(@"%@", tmp); // Shows the number on the display correctly int x = [tmp rangeOfString:@"."].location; NSLog(@"%i", x); // Shows some random signed number if (x < 0) { [display setText:[[display text] stringByAppendingFormat:@"."]]; } It is still not working :(

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  • Is Appfogs pricing model sustainable?

    - by Kyle Finley
    I was looking at AppFog's Pricing and they appear to be giving 2GB of ram away for free, to nonpaying customers. This seems unprecedented for PAAS provodes--providers like Heroku and App Engine remove the app from memory if it has been inactive for certain amount of time. Does cloudfoundry work similarly? Am I wrong in assuming that in a few years appfog servers will be filled with inactive non paying applications?

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