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  • Validates presence of each other in two associated models

    - by Sergey Alekseev
    I have the following two models: class Parent < ActiveRecord::Base has_one :child, dependent: :destroy validates :child, presence: true end class Child < ActiveRecord::Base belongs_to :parent validates :parent, presence: true end I want to create Parent object. If I do the following: Parent.create! or Factory(:parent) Exception raises: ActiveRecord::RecordInvalid: Validation failed: Child can't be blank But I can't create Child object without Parent object for the same reason - I need to create Parent object first in order to pass presence validation. As it appears I have some kind of infinite recursion here. How to solve it?

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  • Consequences in PHP of implementing an interface through two different routes?

    - by Daniel Bingham
    What are the consequences of implementing the same interface through two different routes in PHP, are there any? What I mean, is something like this: interface baseInterface {} abstract class baseClass implements baseInterface { } interface myInterface extends baseInterface {} class myClass extends baseClass implements myInterface {} In this case myClass implements baseInterface from two different parents - myInterface and baseClass. Are there any consequences to this? My instinct is that PHP should handle this fine, but I just want to make sure. What exactly does PHP do in this case? Does it just check to see that the necessary functions are implemented for the interface each time it discovers it and call it a day or does it do something more?

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  • What is the pythonic way to add type information to an object's attributes?

    - by Tikitu
    I'm building classes where I know the types of the attributes, but Python of course doesn't. While it's un-pythonic to want to tell it, supposing I do want to, is there an idiomatic way to do so? Why: I'm reading in serialised data (without type information) involving objects-nested-inside-objects. It's easy to put it into nested dictionaries, but I want it in objects of my class-types, to get the right behaviours as well as the data. For instance: suppose my class Book has an attribute isbn which I will fill with an ISBNumber object. My serialised data gives me the isbn as a string; I would like to be able to look at Book and say "That field should be filled by ISBNumber(theString)." Bonus glee for me if the solution can be applied to classes I get from someone else without editing their code.

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  • [CSS] style input tag

    - by nosferat
    Hi! ASP.Net has a tag called CheckboxList. The output of this tag looks like this: <table class="checkbox"> <tbody> <tr> <td> <input id="/*longdynamicstring1*/" type="checkbox" name="/*longdynamicstring2*/" /> <label for="/*longdynamicstring1*/">Label Text</label> </td> </tr> </tbody> </table> I want to position the label and the input but I cannot find out how. Tried the following: .checkbox input{ padding-right: 5px; } and .checkbox input[type='checkbox'] { padding-right: 5px; } but neither of them had any effect. Because it's ASP I cannot set a class for the input elements and I cannot reference the id because it's dynamic.

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  • C++ MFC add combo box string item from a widget ID

    - by OzBarry
    I've added a combo box in the gui editor in MSVC 2010 pro in my MFC project. I have a list of strings I am grabbing from an external source and want to add them to my combo box. I've searched for a while, and every post seems to suggest I need to use the CComboBox class, however, I have no idea how to get the class variable from the resource ID of the combobox element in the gui editor. In summary, how do I add a string to my combo box, either using a macro (like CB_ADDSTRING(RESOURCE_ID, "my string");) or using CComboBOx (something like CComboBox::GetObject(RESOURCE_ID)->AddString("blah");). I do not do much win32 api/mfc programming, and just started fiddling around with it.

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  • C# NetworkAvailibilityChanged doesn't trigger on disconnect

    - by Nickolay Kondratyev
    My goal is to detect when the Ethernet cable gets disconnected I am attempting to use NetworkChange class but the event NetworkAvailibilityChanged does not trigger when I unplug Ethernet cable. NetworkAddressChanged does get triggered in about 8 seconds but NetworkAvailibilityChanged never does, is there is anything am I am missing? public partial class Form1 : Form { public Form1() { InitializeComponent(); NetworkChange.NetworkAvailabilityChanged += new NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged); NetworkChange.NetworkAddressChanged += new NetworkAddressChangedEventHandler(NetworkChange_NetworkAddressChanged); } void NetworkChange_NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e) { Console.WriteLine("NetworkChange_NetworkAvailabilityChanged"); } void NetworkChange_NetworkAddressChanged(object sender, EventArgs e) { Console.WriteLine("NetworkChange_NetworkAddressChanged"); } }

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  • using JQuery on beforeprint event problem. Not answered.

    - by Cesar Lopez
    Hi all, I have the following function. <script type="text/javascript"> window.onbeforeprint = expandAll; function expandAll(){ $(".fieldset:gt(0)").slideDown("fast"); } </script> For this html <table class="sectionHeader" ><tr ><td>Heading</td></tr></table> <div style="display:none;" class="fieldset">Content</div> I have several block of content over the page, but when I do print preview or print, I can see all divs sliding down before opening the print preview or printing but on the actual print preview or print out they are all collapse. Anyone have any idea why is this? Thanks.

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  • What is the explanation of this results in Java ?

    - by M.H
    I have the following code : public class Main { private int i = j; //1 private int j = 10; public static void main(String[] args) { System.out.println((new Main()).i); } } and there is a compiler error in line 1 because an illegal forward reference. But when I am trying the following code : public class Main { int i = getJ(); //1 int getJ(){ return j; } int j=10; public static void main(String[] args) { System.out.println(new Main().i); } } it works fine and the result is 0.Why there is no illegal forward reference in line 1 here?.The two codes look similar to me.

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  • Unmangling the result of std::type_info::name

    - by terminus
    I'm currently working on some logging code that supposed to - among other things - print information about the calling function. This should be relatively easy, standard C++ has a type_info class. This contains the name of the typeid'd class/function/etc. but it's mangled. It's not very usefull. I.e. typeid(std::vector).name() returns "St6vectorIiSaIiEE". Is there a way to produce something usefull from this? Like 'std::vector' for the above example. If it only works for non-template classes, that's fine too. The sollution should work for gcc, but it would be better if I could port it. It's for logging so it's not so important that it can't be turned of, but it should be helpfull for debugging.

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  • Why we used double pointer in objective-C or C language?

    - by Rajendra Bhole
    Hi, I confused when i want to take single pointer and when should i take double pointer? In following structure what exactly did? struct objc_class { Class isa; Class super_class; const char *name; long version; long info; long instance_size; struct objc_ivar_list *ivars; struct objc_method_list **methodLists; struct objc_cache *cache; struct objc_protocol_list *protocols; }; Why we use the "**methodLists" double pointer?

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  • Templates --> How to decipher, decide if necessary and create?

    - by ML
    Hi All, I have a few classes in a project that I inherited that are really old, last I knew they compiled with CodeWarrior 8. I am not in XCode 3.2 Here is an example of what I struggle with: template <class registeredObject> typename std::vector<registeredObject>::iterator FxRegistry<registeredObject>::begin(void) { return mRegistryList.begin(); } The errors are: no 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' member function declared in class 'FxRegistry<registeredObject>' template definition of non-template 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' How do I decide how to solve these and where do I start looking?

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  • Java: how to represent graphs?

    - by Rosarch
    I'm implementing some algorithms to teach myself about graphs and how to work with them. What would you recommend is the best way to do that in Java? I was thinking something like this: public class Vertex { private ArrayList<Vertex> outnodes; //Adjacency list. if I wanted to support edge weight, this would be a hash map. //methods to manipulate outnodes } public class Graph { private ArrayList<Vertex> nodes; //algorithms on graphs } But I basically just made this up. Is there a better way? Also, I want it to be able to support variations on vanilla graphs like digraphs, weighted edges, multigraphs, etc.

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  • question about c++ template functions taking any type as long that type meets at least one of the re

    - by smerlin
    Since i cant explain this very well, i will start with a small example right away: template <class T> void Print(const T& t){t.print1();} template <class T> void Print(const T& t){t.print2();} This does not compile: error C2995: 'void Print(const T &)' : function template has already been defined So, how can i create a template function which takes any type T as long as that type has a print1 memberfunction OR a print2 memberfunction (no polymorphism) ?

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  • AnimationDrawable, when does it end?

    - by Syb
    I know there have been several people with the same question. Which is: How do i know when a frame by frame animation has ended? I have not had any useful answer on fora i visited. So i thought, let's see if they know at stackoverflow. But I could not sit still in the mean time, so i made a work around of this, but it does not really work the way i would like it to. here is the code: public class Main extends Activity { AnimationDrawable sybAnimation; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ImageView imageView = (ImageView)findViewById(R.id.ImageView01); imageView.setBackgroundResource(R.anim.testanimation); sybAnimation = (AnimationDrawable) imageView.getBackground(); imageView.post(new Starter()); } class Starter implements Runnable { public void run() { sybAnimation.start(); long totalDuration = 0; for(int i = 0; i< sybAnimation.getNumberOfFrames();i++){ totalDuration += sybAnimation.getDuration(i); } Timer timer = new Timer(); timer.schedule(new AnimationFollowUpTimerTask(R.id.ImageView01, R.anim.testanimation_reverse),totalDuration); } } class AnimationFollowUpTimerTask extends TimerTask { private int id; private int animationToRunId; public AnimationFollowUpTimerTask(int idOfImageView, int animationXML){ id = idOfImageView; animationToRunId = animationXML; } @Override public void run() { ImageView imageView = (ImageView)findViewById(id); imageView.setBackgroundResource(animationToRunId); AnimationDrawable anim = (AnimationDrawable) imageView.getBackground(); anim.start(); } } basically I make a timertask which is scheduled with the same time as the animation to take. In that run() I want to load a new animation into the imageView and start that animation, this however does not work. Does anyone know how to get this to work, or even better, have a better way to find out when an AnimationDrawable has ended its animation?

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  • NHibernate: Dynamically swapping a single domain model between multiple physical data models

    - by Nigel
    Hi In this article Ayende describes how to map a single domain model to multiple physical data models. Is it possible to extend this principle such that the mapping can chosen dynamically? So for example, imagine we had an entity that could be written to the same physical schema in three ways depending on its current status, and lets assume that regardless of status each entity had a unique identifier. One solution would be to represent the entity in its different states with three separate classes: one for each mapping. Then the entity could be loaded and in order to change its state the entity could be mapped to a class representing one of its other states and then saved back to the schema, making use of a different mapping. I was wondering if it is at all possible to have the same entity represented by one class that held a status flag (kind of like a discriminator), and any save to the schema would choose the appropriate mapping based on the value of the status flag. Hopefully that made sense! Many thanks.

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  • Why does a Linq Cast<T> operation fail when I have an implicit cast defined?

    - by Ryan Versaw
    I've created two classes, with one of them having an implicit cast between them: public class Class1 { public int Test1; } public class Class2 { public int Test2; public static implicit operator Class1(Class2 item) { return new Class1{Test1 = item.Test2}; } } When I create a new list of one type and try to Cast<T> to the other, it fails with an InvalidCastException: List<Class2> items = new List<Class2>{new Class2{Test2 = 9}}; foreach (Class1 item in items.Cast<Class1>()) { Console.WriteLine(item.Test1); } This, however, works fine: foreach (Class1 item in items) { Console.WriteLine(item.Test1); } Why is the implicit cast not called when using Cast<T>?

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  • A basic animation not showing up

    - by Rilakkuma
    I still try different basics with android, and now I'm stuck with animation. I'm trying to implement a simple animation. I've defined animation in xml file like this: alpha android:interpolator="@android:anim/accelerate_interpolator" android:fromAlpha="0.0" android:toAlpha="1.0" duration="3000" repeatCount="infinite" In my main view group I have an ImageView defined like this: <ImageView android:id="@+id/someb" android:src="@drawable/earth_normal" android:layout_width="wrap_content" android:layout_height="wrap_content" android:padding="5dip"/> And this is from my starting activity class: public class Ohayou extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); ImageView earth = (ImageView)findViewById(R.id.someb); Animation earthFadeInAnimation = AnimationUtils.loadAnimation(this, R.anim.fade_in); earth.startAnimation(earthFadeInAnimation); } It finds ImageView successfuly and creates animation. but when I start emulator ImageView just shows the original src image, not an animation. What am I doing wrong? Thanks

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  • jQuery switchClass

    - by Eric
    Is it possible to undo a switchClass transaition? I'd like an element to slowly obtain class A as you hover over it, and slowly lose it again once the mouse has moved away. However, the function appears to be glitchy, and calling .stop(0,1) doesn't seem to help. In fact, it seems to break it. I have a live example here. Yes, it's a 404 page, but that's not important. The navigation should be slowly gaining or losing a class, but it just jumps. The script can be found here. Is such a transition possible?

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  • Interface with generic parameters- can't get it to compile

    - by user997112
    I have an interface like so: public interface MyInterface<E extends Something1> { public void meth1(MyClass1<E> x); } and I have a subclass whose superclass implements the above interface: public class MyClass2<E extends Something1> extends Superclass{ public MyClass2(){ } public void meth1(MyClass1 x) { // TODO Auto-generated method stub } } superclass: public abstract class Superclass<E extends Something1> implements MyInterface{ MyClass1<E> x; protected E y; public Superclass(){ } } the problem is that the parameter for meth1() is supposed to be generic. If I do MyClass1 it doesn't like it and the only way I can get it to compile is by leaving out generic parameters- which feels wrong. What's going wrong?

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  • how to structure code that uses std::rel_ops

    - by R Samuel Klatchko
    I was working on some code and wanted to make use of std::rel_ops. From what I can tell, you need to do using std::rel_ops to your source code to make use of them. But I'm not sure where the best place to put that is. Let's say I have a header file with a class that only defines the minimal operator== and operator<: // foo.h class foo { public: bool operator==(const foo &other) const; bool operator<(const foo &other) const; }; I'm not sure where to put using std::rel_ops. If I leave it out of the foo.h, then every user of foo.h needs to know the implementation detail that foo is not defining all the operators itself. But putting using std::rel_ops inside foo.h breaks the rule of thumb about not having a using in a header file. How do other people resolve this issue?

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  • Java - Syntax Question: What is <? super T>

    - by aloh
    I'm having trouble understanding the following syntax: public class SortedList< T extends Comparable< ? super T> > extends LinkedList< T > I see that class SortedList extends LinkedList. I just don't know what T extends Comparable< ? super T> means. My understanding of it so far is that type T must be a type that implements Comparable...but what is "< ? super T "?

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  • Instantiation vs. Typed reference

    - by Farstucker
    Just when I think Im starting to understand the basics, I find something that brings me right back to reality. In this case, typed reference. I found an example similar to this: class Worker { Boss boss; public void Advise(Boss pBoss) { this.boss = pBoss; } How can you reference methods within the Boss class if its not static and not instantiated? I guess my real question is whats the difference between: Boss boss; and Boss boss = new Boss(); Thank you, FS

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  • [C#] How to share a variable between two classes?

    - by Altefquatre
    Hello, How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it? Thanks Altefquatre

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  • Hide twitter bootstrap popover

    - by soft genic
    Following is my jquery code which i am using to display popover . What i wanna do is when a user click anywhere on the screen or on any <span id="close" class="pover"></span> then it hides the current opened popover and show a new popover on which the user clicks on. As You can see below span which contains class="pover" are being poped up by the following jquery kindly let me know how can i hide the opened popup and display a new one accordingly Currently, all the popover are getting displayed on click event. $(document).ready(function() { $('.pover').each(function() { //$('#close').popover( "hide" ); $(this).popover({ title: $(this).attr('abc'), content: $(this).attr('data-content'), delay: "show", trigger: "click" }); }); });

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  • How does compiling circular dependencies work?

    - by Fabio F.
    I've made the example in Java but I think (not tested) that it works in other (all?) languages. You have 2 files. First, M.java: public class MType { XType x; MType() {x = null;} } Second, another file (in the same directory), XType.java: public class XType { MType m; public XType(MType m) {this.m = m;} } Ok it's bad programming, but if you run javac XType it compiles: compiles even MType because XType needs it. But ... MType needs XType ... how does that work? How does the compiler know what is happening? Probably this is a stupid question, but I would like to know how the compiler (javac or any other compilers you know) manages that situation, not how to avoid it. I'm asking because i'm writing a precompiler and I would like to manage that situation.

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