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• What data (if any) persists across web-requests in Ruby on Rails?

  - by Daniel Beardsley

  I decided to use the singleton design pattern while creating a view helper class. This got me thinking; will the singleton instance survive across requests? This led to another question, Which variables (if any) survive across web requests and does that change depending on deployment? (Fastcgi, Mongrel, Passenger, ...) I know that Controller instance variables aren't persisted. I know Constants are persisted (or reloaded?). But I don't know about class variables, instance variables on a class, Eigenclasses, ...

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• Why can't I enforce derived classes to have parameterless constructors?

  - by FrisbeeBen

  I am trying to do the following: public class foo<T> where T : bar, new() { public foo() { _t = new T(); } private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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• ActiveRecord, has_many, polymorphic and STI

  - by leomayleomay

  I've came into a problem while working with AR and polymorphic, here's the description, class Base < ActiveRecord::Base; end class Subscription < Base set_table_name :subscriptions has_many :posts, :as => :subscriptable end class Post < ActiveRecord::Base belongs_to :subscriptable, :polymorphic => true end in the console, >> s = Subscription.create(:name => 'test') >> s.posts.create(:name => 'foo', :body => 'bar') and it created a Post like: #<Post id: 1, name: "foo", body: "bar", subscriptable_type: "Base", subscriptable_id: 1, created_at: "2010-05-10 12:30:10", updated_at: "2010-05-10 12:30:10"> the subscriptable_type is Base but Subscription, anybody can give me a hand on this?

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• Disabled button working in my View page using jquery

  - by kumar

  <% using (Html.BeginForm("Student", "Home", FormMethod.Post, new { @id = "exc-"})) { %> this is my Beginform and I have buttons in my view.. <fieldset> <div> <input id="btnSelectAll" type="button" class="button" value="Select All" /> <input id="btnSubmit" type="submit" class="button" value="Save" /> <input id="btnCancel" type="button" class="button" value="Cancel" /> </div> </fieldset> On document load I am doing disabling my submit button $('#btnSubmit').attr('disabled','disabled'); $('#btnCancel').attr('disabled','disabled'); I am seeing My buttons are Disabled but when I click on Save button still its going to my controler? please can anybody tell me why its doing like this?

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• jquery .load() function only gets called once

  - by user1288099

  the html <div class="stackwrapper" id="user1"></div> <div class="stackwrapper" id="user2"></div> <div class="userdrawings"></div> the javascript $('.stackwrapper').click(function(e){ var id=$(this).attr('id'); $('.userdrawings').load('loadSession.php?user='+id).fadeIn("slow"); }); Somehow it only works at once, only at the first click on stackwrapper, when I click on the second one, the function is not triggered again.

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• AngularJS: Better way to display success messages

  - by Sup

  $('body').on('click', '#save-btn', function () { $('#greetingsModal').modal('show'); }); <div id="greetingsModal" class="modal hide fade" tabindex="-1" role="dialog" aria- labelledby="myModalLabel" aria-hidden="true"> <div class="alert alert-success"> <a href="../admin/Supplier" class="close" data-dismiss="alert">x</a> <strong>Well done!</strong>. </div> I want to display a popup message using the above styles whenever 'save-btn' is clicked. The above code works fine but there is a lot of time delay by doing it this way. Is there any way to display such a alert message using angular?

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• Problems with ActiveRecord assoc

  - by ciss

  Hello again, so i write my e-commerce shop cms and have some strange error: ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'id' in 'where clause': DELETE FROM `properties` WHERE `id` = NULL so, i have three models Items: class Item < ActiveRecord::Base has_many :properties, :dependent => :destroy has_many :types, :through => :property end Type: class Type < ActiveRecord::Base has_many :properties, :dependent => :destroy end Properties: class Property < ActiveRecord::Base belongs_to :item belongs_to :type end So, all is okay, but when i try to item.destroy() i have error =( This is my test code: test "should destroy associated properties" do item = Item.create(:name => "Jeans") type = Type.create(:key => "color") property = Property.new property.item = item property.type = type property.save item.destroy() end

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• Force result for empty() test on an object

  - by hsz

  Hello ! Simple class for example: class Foo { protected $_bar; public function setBar( $value ) { $this->_bar = $value; } } And here is the question: $obj = new Foo(); var_dump( empty( $obj ) ); // true $obj->setBar( 'foobar' ); var_dump( empty( $obj ) ); // false Is it possible to change class's behaviour with testing it with empty() function so it will returns true when object is not filled with data ? I know about magic function __isset( $name ) but it is called only when we test specific field like: empty( $obj->someField ); but not when test whole object.

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• Why is it possible to save entity but not delete if transactional annotation is set to readonly=true

  - by jakob

  Hello experts! My class is annotated with org.springframework.transaction.annotation.Transactional like this: @Transactional(readOnly = true) public class MyClass { I then have a dao class: @Override public void delete(final E entity) { getSession().delete(entity); } @Override public void save(final E entity) { getSession().saveOrUpdate(entity); } Then I have two methods in MyClass @Transactional(readOnly = false) public void doDelete(Entity entity){ daoImpl.delete(entity) } //@Transactional(readOnly = false) public void doSave(){ daoImpl.save(entity) } Saving and deleting works like a charm. But if I remove the @Transactional(readOnly = false) on doDelete method deletion stops working, Saving works with and without the method annotation. So my question is: WHY?

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• What's the difference between => , ()=>, and Unit=>

  - by Malvolio

  I'm trying to represent a function that takes no arguments and returns no value (I'm simulating the setTimeout function in JavaScript, if you must know.) case class Scheduled(time : Int, callback : => Unit) doesn't compile, saying " `val' parameters may not be call-by-name" case class Scheduled(time : Int, callback : () => Unit) compiles, but has to be invoked strangely, instead of Scheduled(40, { println("x") } ) I have to do this Scheduled(40, { () => println("x") } ) What also works is class Scheduled(time : Int, callback : Unit => Unit) but is invoked in an even-less-sensible way Scheduled(40, { x : Unit => println("x") } ) (What would a variable of type Unit be?) What I want of course is a constructor that can be invoke the way I would invoke it if it were an ordinary function: Scheduled(40, println("x") ) Give baby his bottle!

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• Parsing data without HMLT tags

  - by user296507

  Hi, I need to extract the actual phone number form the html listed below, but I'm not really sure how to do it using Nokogiri CSS since there are no html tags around it. When an at_css(.phonetitle) it only parse Phone and not the number. <div class="detail"> <span class="address">Corner of Toorak Road and Chapel Street, South Yarra</span><br> <span class="phonetitle">Phone</span> 95435 34341 <br><br> </div>

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• Ruby forwarding method calls

  - by JP

  I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance. At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?) class Master def initalize(mynum) @mynum = mynum end def one_thing(subinstance) "One thing with #{subinstance.var} from #{@mynum}" end def four_things(subinstance) "Four things with #{subinstance.var} from #{@mynum}" end def many_things(times,subinstance) "#{times} things with #{subinstance.var} from #{@mynum}" end def make_a_sub(uniqueness) Subthing.new(uniqueness,self) end class Subthing def initialize(uniqueness,master) @u = uniqueness @master = master end # Here I'm forwarding method calls def one_thing master.one_thing(self) end def four_things master.four_things(self) end def many_things(times) master.many_things(times,self) end end end m = Master.new(42) s = m.make_a_sub("very") s.one_thing === m.one_thing(s) s.many_things(8) === m.many_things(8,s) I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either) Thanks for reading!

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• Changing the value of a macro at run time

  - by BrandiNo

  I'm working in Visual Studio 2010, using C++ code. What I'm trying to do is change the value of a preprocessor directive during run time, not sure if it's possible but i've tried this.. somefile.h static int mValue = 0; #define POO = mValue; ... #if POO 0 //define class methods #else //define class methods differently } main.cpp main() { //Code calls constructor and methods allowed when POO is 0 //Code increments mValue //Code calls constructor and methods allowed when POO is 1 } How can POO be changed so that class objects uses a different implementation of other methods? Or if it's not possible, what's a another approach to this?

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• Nested form child only updates if parent changes.

  - by chap

  In this video (10 sec) you can see that the nested attribute is only updated if it's parent model is changed. Using rails 3.0.0.beta and full project is on github. Summary of models and form: class Project < ActiveRecord::Base has_many :tasks accepts_nested_attributes_for :tasks end class Task < ActiveRecord::Base belongs_to :project has_many :assignments accepts_nested_attributes_for :assignments end class Assignment < ActiveRecord::Base belongs_to :task end form_for(@project) do |f| Project: f.text_field :name f.fields_for :tasks do |task_form| Task: task_form.text_field :name task_form.fields_for :assignments do |assignment_form| Assignment: assignment_form.text_field :name end end f.submit end

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• is there an equivalent to a "Focus Listener" in Objective-C or iPhone SDK? (Coming from Java)

  - by MarcZero

  Hello. I am a student programmer who has taken up Objective-C on my free time as my college doesn't teach it. We have only used Java and basic C so far. I am in the middle of making a program for the iPod and was wondering if there was any type of way to call a method in a class similar to the way a Focus Listener does in Java? I have a view that I would like to call a refresh method (to update the newly inputted titles of buttons from another view) when the view is put at the top and visible again. Is this too easy or is there a more methodical way of doing that? I have tried to just call the method from the other view class but it does not seem to work (says the other class is either undefined or may not accept the method call and crashes on execution). Any insight would be appreciated. Thank you for your time.

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• start intent without onCreate {}

  - by melvintcs

  i create a class extend Gallery and there is no onCreate, and i having a problem to run my intent. this is my sample code: this.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View v, int position, long id) { Intent intent = new Intent(v.getContext(), ClassName.class); startActivity(intent); }} i also tried below code to run, failed me also: Intent intent = new Intent(ThisClassName.this, ClassName.class); startActivity(intent); Please advice me what should i do :)

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• Is it possible in Scala to force the caller to specify a type parameter for a polymorphic method ?

  - by Alex Kravets

  //API class Node class Person extends Node object Finder { def find[T <: Node](name: String): T = doFind(name).asInstanceOf[T] } //Call site (correct) val person = find[Person]("joe") //Call site (dies with a ClassCast inside b/c inferred type is Nothing) val person = find("joe") In the code above the client site "forgot" to specify the type parameter, as the API writer I want that to mean "just return Node". Is there any way to define a generic method (not a class) to achieve this (or equivalent). Note: using a manifest inside the implementation to do the cast if (manifest != scala.reflect.Manifest.Nothing) won't compile ... I have a nagging feeling that some Scala Wizard knows how to use Predef.<:< for this :-) Ideas ?

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• template specilization using member enums

  - by Altan

  struct Bar { enum { Special = 4 }; }; template<class T, int K> struct Foo {}; template<class T> struct Foo<T::Special> {}; Usage: Foo<Bar> aa; fails to compile using gcc 4.1.2 It complains about the usage of T::Special for partial specilization of Foo. If Special was a class the solution would be to a typename in front of it. Is there something equivalent to it for enums (or integers)? Thanks, Altan

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• Windows Form Components Access

  - by rxm0203

  What is the best way to access components (e.g. imagelist, timer) from a form instance? I am working on multi form windows forms application on .NET Compact Framework version 3.5 SP1 with C#. I have a Controller class associated with each form for MVC implementation. Here is my sample Controller class. public class Controller { public void Init(Form f) { //f.Controls will allow access to all controls //How shall I access imagelist, timer on form f. } } My question is how can I access non visual components without taking a performance hit of reflection? Any code snippets are welcome. If reflection is only way, then can you provide me optimal way for components access please? Thanks,

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• Accessing primitive properties from objects stored in a NSDictionary

  - by ChrisS

  Apologies if this is a basic question, I am just starting with Objective-C and trying to wrap things around in my head! I have a simple class of the form: @interface Whatever : NSObject { int somePrimitive; SomeObject* someObject; } @property (nonatomic) int somePrimitive; @property (nonatomic, retain) SomeObject* someObject; The class is more involved that this, but this illustrates the purpose. When I store instances of this class in a NSMutableDictionary: Whatever *whatever = [[Whatever alloc] init]; whatever.somePrimitive = 1; whatever.someObject = ...; [myDictionary setObject:whatever forKey:@"someKey"]; and then try to retrieve the object later: Whatever *result = [myDictionary valueForKey:@"someKey"]; then, result.someObject is ok to reference but, result.somePrimitive crashes. Does the NSDictionary not copy over the primitives of the object? Is the rule that the object stored in a dictionary should only contain objects?

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• What is the definition of a Service object ?

  - by Maskime

  I've been working a lot with PHP. But recently i was sent on a work wich use Java. In PHP i used to do a lot of Singleton object but this pattern has not the same signification in Java that it has in PHP. So i wanted to go for an utility class (a class with static method) but my chief doesn't like this kind of classes and ask me to go for services object. So my guess was that a service object is just a class with a constructor that implement some public methods... Am i right ?

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• C# Anyway to detect if an object is locked.

  - by scope-creep

  Hi, Is their anyway to determine if a object is locked in c#. I have the unenviable position, through design where i'm reading from a queue inside a class, and I need to dump the contents into a collection in the class. But that collection is also read/write from an interface outside the class. So obviously their may be a case when the collection is being written to, as the same time i want to write to it. I could program round it, say using delegate but it would be ugly. Bob.

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• How to use multiple restrictions in C# Generics properly?

  - by plouh

  I am attempting to bind c# generics to a class and an interface like this: public class WizardPage<T> where T : UserControl, IWizardControl { private T page; public WizardPage( T page ) { this.page = page; } } And use it with this: public MyControl : UserControl, IWizardControl { //... } Somehow C# doesn't seem to be able to decide that MyControl is a proper instance of T as public class Wizard<T> where T : UserControl, IWizardControl { private WizardPage<T> Page1; public Wizard( MyControl control ) { this.Page1 = new WizardPage(control); } } fails with error The best overloaded method match for 'Controls.WizardPage.WizardPage(T)' has some invalid arguments Am I doing something wrong or is this just not going to work?

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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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