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  • sqlalchemy: what is the difference between declaring the cascade within the foreign key vs relation?

    - by steve
    what is the difference between declaring the cascade within a foreign key vs relations? class Contact(Base): __tablename__ = 'contacts' id = Column(Integer, primary_key=True) addresses = relation("Address", backref="contact") class Address(Base): __tablename__ = 'addresses' id = Column(Integer, primary_key=True) contact_id = Column(Integer, ForeignKey('contact.id', onupdate="CASCADE", ondelete="CASCADE"))) vs class Contact(Base): __tablename__ = 'contacts' id = Column(Integer, primary_key=True) addresses = relation("Address", backref="contact", cascade="all, delete-orphan") class Address(Base): __tablename__ = 'addresses' id = Column(Integer, primary_key=True) contact_id = Column(Integer, ForeignKey('contact.id')) with the foreign key declaration, it seems like the cascade is enforced at the database level. how does the relations approach work? thanks!

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  • mysql eliminate responses under certain condition with join

    - by Dustin
    Forgive me if this is an easy question. I teach classes and want to be able to select those students who have taken one class, but not another class. I have two tables: lessons_slots which is the table for every class such as: -------------------- -ID name slots- -1 basics 10 - -2 advanced 10 - -3 basics 10 - --------------------- The other table is class_roll, which holds enrollment info, such as: -------------------- -sID classid firstname lastname- -1 1 Jo Schmo -2 1 Person Two ... -13 2 Jo Schmo --------------------- What I want to do, I select everyone who has not had the advanced class (for example). I've tried doing SELECT * FROM lessons_slots LEFT JOIN class_roll ON lessons_slots.ID = class_roll.classid WHERE lessons_slots.name != 'advanced' But that doesn't work. Any ideas?

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  • Conting of objects created in stack and heap for many classes

    - by viswanathan
    What is the best way to count the total number of objects created in both stack and heap for different classes. I know that in C++ new and delete operators can be overloaded and hence in the default constructor and destructor the object count can be incremented or decremented as and when the objects get created or destroyed. Further if i am to extend the same thing for object counting of objects of different classes, then i can create a dummy class and write the object count code in that class and then when i create any new class i can derive it from the Dummy class. Is there any other optimal solution to the same problem.

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  • What is Ruby's double-colon (::) all about?

    - by Meltemi
    I'd probably be able to answer this for myself if "::" wasn't so hard to Google. Didn't see anything on SO so thought I'd try my luck. What is this double-colon :: all about? I see it everywhere in Rails: class User < ActiveRecord::Base or… ActionController::Routing::Routes.draw do |map| I found a definition from this guy: The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module. but that just leads to more questions. What good is scope (private, protected) if you can just use :: to expose anything?

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  • Paste a multi-line Java String in Eclipse

    - by Thilo
    Unfortunately, Java has no syntax for multi-line string literals. No problem if the IDE makes it easy to work with constructs like String x = "CREATE TABLE TEST ( \n" + "A INTEGER NOT NULL PRIMARY KEY, \n" ... What is the fastest way to paste a multi-line String from the clipboard into Java source using Eclipse (in a way that it automagically creates code like the above).

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  • Using Rails and Rspec, how do you test that the database is not touched by a method

    - by Will Tomlins
    So I'm writing a test for a method which for performance reasons should achieve what it needs to achieve without using SQL queries. I'm thinking all I need to know is what to stub: describe SomeModel do describe 'a_getter_method' do it 'should not touch the database' do thing = SomeModel.create something_inside_rails.should_not_receive(:a_method_querying_the_database) thing.a_getter_method end end end EDIT: to provide a more specific example: class Publication << ActiveRecord::Base end class Book << Publication end class Magazine << Publication end class Student << ActiveRecord::Base has_many :publications def publications_of_type(type) #this is the method I am trying to test. #The test should show that when I do the following, the database is queried. self.publications.find_all_by_type(type) end end describe Student do describe "publications_of_type" do it 'should not touch the database' do Student.create() student = Student.first(:include => :publications) #the publications relationship is already loaded, so no need to touch the DB lambda { student.publications_of_type(:magazine) }.should_not touch_the_database end end end So the test should fail in this example, because the rails 'find_all_by' method relies on SQL.

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  • Shared static classes between AppDomains in loaded library code

    - by Christian Stewart
    I'm working on a program in which I want to do something similar to what the Photon Server system does: Offer a common "API" class library, which contains common data classes, enumerations, and interfaces for working with the host program. Have client programs (class libraries) reference this DLL and implement interfaces listed within it. Have the "host" application load built DLL client libraries into separate AppDomains and reference the interfaces that lie within to have polymorphic client code from within a dll file. I have something like this worked out: a class library that contains common code, but I've run into the following question How should I handle static classes? Should I add a method that is called by the host program to synchronize data? How do I keep a static class the same between AppDomains? Should I discard these classes in favor of better interfaces between the code levels? And in general, how do I share data between these loaded AppDomains?

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  • Select CSS based on multiple classes

    - by Stacey
    I have a style rule I want to apply to a tag when it has TWO styles. Is there any way to perform this without javascript? In other words.. <li class='left ui-class-selector'> I want to select only if the li has both 'left' and 'ui-class-selector' classes applied.

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  • How to set order of appearance for fields when using Html.EditorFor in MVC 2?

    - by Anrie
    I have the following classes in my Model: public abstract class Entity : IEntity { [ScaffoldColumn(false)] public int Id { get; set; } [Required,StringLength(500)] public string Name { get; set; } } and public class Model : SortableEntity { [Required] public ModelType Type { get; set; } [ListRequired] public List<Producer> Producers { get; set; } public List<PrintArea> PrintAreas { get; set; } public List<Color> Colors { get; set; } } To display the "Model" class in the view I simply call Html.EditorFor(model=model), but the "Name" property of the base class is rendered last, which is not the desired behaviour. Is it possible to influenece on the order of displayed fields somehow?

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  • The Java interface doesn't declare any exception. How to manage checked exception of the implementat

    - by Frór
    Let's say I have the following Java interface that I may not modify: public interface MyInterface { public void doSomething(); } And now the class implementing it is like this: class MyImplementation implements MyInterface { public void doSomething() { try { // read file } catch (IOException e) { // what to do? } } } I can't recover from not reading the file. A subclass of RuntimeException can clearly help me, but I'm not sure if it's the right thing to do: the problem is that that exception would then not be documented in the class and a user of the class would possibly get that exception an know nothing about solving this. What can I do?

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  • What are the requirments for ISupportInitialize code to be serialized in InitializeComponent? .Net

    - by Jules
    I need to add some code to the EndInit method of a PictureBox control but unfortunately its private and, from what I can gather, I can't shadow it and call base - at least not in VB.Net. What I can do is add a dummy property to my picture box class. The type of the dummy property is simply a class that just implements ISupportInitialize. However, that doesn't work, I need the dummy class to inherit from Control. Is that the minimum requirement?

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  • Validating an Autocomplete field in Django

    - by anonymous coward
    I have models similar to the following: class Band(models.Model): name = models.CharField(unique=True) class Event(models.Model): name = models.CharField(max_length=50, unique=True) bands = models.ManyToManyField(Band) and essentially I want to use the validation capability offered by a ModelForm that already exists for Event, but I do not want to show the default Multi-Select list (for 'bands') on the page, because the potential length of the related models is extremely long. I have the following form defined: class AddEventForm(ModelForm): class Meta: model = Event fields = ('name', ) Which does what is expected for the Model, but of course, validation could care less about the 'bands' field. I've got it working enough to add bands correctly, but there's no correct validation, and it will simply drop bad band IDs. What should I do so that I can ensure that at least one (correct) band ID has been sent along with my form? For how I'm sending the band-IDs with auto-complete, see this related question: http://stackoverflow.com/questions/1528059/

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  • Makefile to compile both C and Java programs at the same time

    - by user342745
    I have three programs that need to be compiled at the same time, 2 written in C and 1 in java. I had all three working with the Makefile when they were in C, but then switched one of them to java... is there a way to compile all 3 at once with the same makefile? Here is my current Makefile: CC=gcc JC=javac JFLAGS= -g CFLAGS= -Wall -g -std=c99 LDFLAGS= -lm .SUFFIXES: .java .class .java.class: $(JC) $(JFLAGS) $*.java CLASSES = kasiski.java kentry.java ALL= ic ftable kasiski all: $(ALL) ic: ic.o kasiski: $(CLASSES:.java=.class) ftable: ftable.o ic.o: ic.c ic.h ftable.o: ftable.c ftable.h .PHONY: clean clean: rm -rf core* *.class *.o *.gch $(ALL)

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  • Best way to implement game loop without freezing UI thread

    - by Matt H
    I'm trying to make a simple 2D game in Java. So far I have a JFrame, with a menubar, and a class which extends JPanel and overrides it's paint method. Now, I need to get a game loop going, where I will update the position of images and so on. However, I'm stuck at how best to achieve this. Should I use multi-threading, because surely, if you put an infinite loop on the main thread, the UI (and thus my menu bar) will freeze up? Here's my code so far: import java.awt.Color; import java.awt.Graphics; import javax.swing.JPanel; @SuppressWarnings("serial") public class GameCanvas extends JPanel { public void paint(Graphics g) { while (true) { g.setColor(Color.DARK_GRAY); try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } } } } import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; @SuppressWarnings("serial") public class Main extends JFrame { GameCanvas canvas = new GameCanvas(); final int FRAME_HEIGHT = 400; final int FRAME_WIDTH = 400; public static void main(String args[]) { new Main(); } public Main() { super("Game"); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenuItem startMenuItem = new JMenuItem("Pause"); menuBar.add(fileMenu); fileMenu.add(startMenuItem); super.add(canvas); super.setVisible(true); super.setSize(FRAME_WIDTH, FRAME_WIDTH); super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); super.setJMenuBar(menuBar); } } Any pointers/tips? Also, where should I put my loop? In my main class, or my GameCanvas class? Any help is appreciated, thanks.

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  • preload image with jquery

    - by robertdd
    ok, I spent 2 days trying to preloaded images but no succes! i have this function: jQuery.getlastimage = function(id) { $.getjs(); $.post('operations.php', {'operation':'getli', 'id':id,}, function(lastimg){ $("#upimages" + id).html('<a href="uploads/'+ lastimg +'?'+ (new Date()).getTime() +'"><img class="thumbs" id="' + id + '" alt="' + lastimg + '" src="uploads/' + lastimg +'?'+ (new Date()).getTime() + '" /></a>'); }); }; while the image loading i want to appear a gif or a text "Loading...". the function will get something like this: <div class="upimage"> <ul class="thumbs" id="upimagesQueue"> **<li id="#upimagesRIFDIB"> <a href="uploads/0001.jpg?1271800088379"> <img src="uploads/0001.jpg?1271800088379" alt="0001.jpg" id="RIFDIB" class="thumbs"> </a> </li>** <li> .... </li> </ul> </div> i tryed like this: ... $.post('operations.php', {'operation':'getli', 'id':id,}, function(lastimg){ $("#upimages" + id) .html('<a href="uploads/'+ lastimg +'?'+ (new Date()).getTime() +'"><img class="thumbs" id="' + id + '" alt="' + lastimg + '" src="uploads/' + lastimg +'?'+ (new Date()).getTime() + '" /></a>') .hide() .load(function() { $(this).show(); }); ... but all the <li> will hide and after is loading the image appear, i want the <li> to apear with a gif or a text in it and after the image is loaded the link and the image to apear! How to do this? Anyone have an idea? Thanks!

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  • Ruby core documentation quality

    - by karatedog
    I'm relatively new to Ruby and have limited time therefore I try out simple things. Recently I needed to create a file and because I'm lazy as hell, I run to Google. The result: File.open(local_filename, 'w') {|f| f.write(doc) } Shame on me, it is very straightforward, should have done it myself. Then I wanted to check what ruby magic the File class' methods offer or if there's any 'simplification' when invoking those methods, so I headed for the documentation here, and checked for the File class. 1.8.6 documentation presents me with "ftools.rb: Extra tools for the File class" under 'File' class, which is not what I'm looking for. 1.8.7 documentation seems OK for 'File' class, there are a plethora of methods. Except 'open'. 1.9 documentation finally shows me the 'open' method. And I had an almost same tour with Net::HTTP. Do I exaggerate when I think good old Turbo Pascal's 7.0 documentation was better organized than Ruby documentation is right now? Is there any other source for the uninitiated to collect knowledge? Or is it possible that I just tumbled into a documentation hole and the rest are super-brilliant-five-star organized? Thanks

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  • Scala: Correcting type inference of representation type over if statement

    - by drhagen
    This is a follow-up to two questions on representation types, which are type parameters of a trait designed to represent the type underlying a bounded type member (or something like that). I've had success creating instances of classes, e.g ConcreteGarage, that have instances cars of bounded type members CarType. trait Garage { type CarType <: Car[CarType] def cars: Seq[CarType] def copy(cars: Seq[CarType]): Garage def refuel(car: CarType, fuel: CarType#FuelType): Garage = copy( cars.map { case `car` => car.refuel(fuel) case other => other }) } class ConcreteGarage[C <: Car[C]](val cars: Seq[C]) extends Garage { type CarType = C def copy(cars: Seq[C]) = new ConcreteGarage(cars) } trait Car[C <: Car[C]] { type FuelType <: Fuel def fuel: FuelType def copy(fuel: C#FuelType): C def refuel(fuel: C#FuelType): C = copy(fuel) } class Ferrari(val fuel: Benzin) extends Car[Ferrari] { type FuelType = Benzin def copy(fuel: Benzin) = new Ferrari(fuel) } class Mustang(val fuel: Benzin) extends Car[Mustang] { type FuelType = Benzin def copy(fuel: Benzin) = new Mustang(fuel) } trait Fuel case class Benzin() extends Fuel I can easily create instances of Cars like Ferraris and Mustangs and put them into a ConcreteGarage, as long as it's simple: val newFerrari = new Ferrari(Benzin()) val newMustang = new Mustang(Benzin()) val ferrariGarage = new ConcreteGarage(Seq(newFerrari)) val mustangGarage = new ConcreteGarage(Seq(newMustang)) However, if I merely return one or the other, based on a flag, and try to put the result into a garage, it fails: val likesFord = true val new_car = if (likesFord) newFerrari else newMustang val switchedGarage = new ConcreteGarage(Seq(new_car)) // Fails here The switch alone works fine, it is the call to ConcreteGarage constructor that fails with the rather mystical error: error: inferred type arguments [this.Car[_ >: this.Ferrari with this.Mustang <: this.Car[_ >: this.Ferrari with this.Mustang <: ScalaObject]{def fuel: this.Benzin; type FuelType<: this.Benzin}]{def fuel: this.Benzin; type FuelType<: this.Benzin}] do not conform to class ConcreteGarage's type parameter bounds [C <: this.Car[C]] val switchedGarage = new ConcreteGarage(Seq(new_car)) // Fails here ^ I have tried putting those magic [C <: Car[C]] representation type parameters everywhere, but without success in finding the magic spot.

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  • How to implement "select sum()" in Grails

    - by xain
    I have a relationship like this: class E { string name hasMany = [me:ME] } class M { float price } class ME { E e M m int quantity } And I'd hate to iterate to achieve this: "obtain the sum of the quantity in ME times the price of the corresponding M for a given E". Any hints on how to implement it using GORM/HQL ? Thanks in advance

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  • When I change templates in Netbeans, why doesn't anything happen?

    - by Matthew
    I want to modify the "Java class" template, so that the class javadoc comment includes more than just the author. In Netbeans 6.8., I go to Tools Templates Java Java Class, and modify the template. However, nothing seems to change. I tried restarting Netbeans, just in case, but the old template is still used. How do I get Netbeans to recognize changes to the template for Java Classes?

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  • use JQuery to get a list of classes

    - by John
    Hi I have a un-ordered (ul) html list. Each li item has 1 or more classes attached to it. I want to go through this ul list and get all the (distinct) classes. Then from this list create a list of checkboxes who's value matches that of the class and also who's label matches that of the class. One checkbox for each class. What is the best way to do this using JQuery? Thanks

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  • How can I "override" deepcopy in Python?

    - by Az
    Hi there, I'd like to override __deepcopy__ for a given SQLAlchemy-mapped class such that it ignores any SQLA attributes but deepcopies everything else that's part of the class. I'm not particularly familiar with overriding any of Python's built-in objects in particular but I've got some idea as to what I want. Let's just make a very simple class User that's mapped using SQLA. class User(object): def __init__(self, user_id, name): self.user_id = user_id self.name = name I've used dir() to see, before and after mapping, what SQLAlchemy-specific attributes there are and I've found _sa_class_manager and _sa_instance_state. Provided those are the only ones how would I ignore that when defining __deepcopy__? Also, are there any attributes the SQLA injects into the mapped object? (I asked this in a previous question (as an edit a few days after I selected an answer to the main question, though) but I think I missed the train there. Apologies for that.)

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  • ADO Exception in HQL query

    - by Yoav
    I have 2 classes: Project and DataStructure. Class Project contains member List<DataStructure. My goal is to load a Project and all its DataStructures in one call. public class Project { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual ISet<DataStructure> DataStructures { get { } set { } } } public class DataStructure { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual string Description { get { } set { } } public virtual Project Project { get { } set { } } public virtual IList<DataField> Fields { get { } set { } } } Note that DataStructure also contains a list of class DataField but I don’t want to load these right now. Mapping in Fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Table("PROJECTS"); Id(x => x.Pk, "PK"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); HasMany<DataStructure>(x => x.DataStructures).KeyColumn("FK_PROJECT"); } } public class DataStructureMap : ClassMap<DataStructure> { public DataStructureMap() { Table("DATA_STRUCTURES"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); Map(x => x.Description, "DESCRIPTION"); References<Project>(x => x.Project, "FK_PROJECT"); HasMany<DataField>(x => x.Fields).KeyColumn("FK_DATA_STRUCTURE"); } } This is my query: using (ISession session = SessionFactory.OpenSession()) { IQuery query = session.CreateQuery("from Project pr left join pr.DataStructure"); project = query.List<Project>(); } query.List() returns this exception: NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available] ---> System.ArgumentException: The value "System.Object[]" is not of type "Project" and cannot be used in this generic collection.

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  • I am confused about how to use @SessionAttributes

    - by yusaku
    I am trying to understand architecture of Spring MVC. However, I am completely confused by behavior of @SessionAttributes. Please look at SampleController below , it is handling post method by SuperForm class. In fact, just field of SuperForm class is only binding as I expected. However, After I put @SessionAttributes in Controller, handling method is binding as SubAForm. Can anybody explain me what happened in this binding. ------------------------------------------------------- @Controller @SessionAttributes("form") @RequestMapping(value = "/sample") public class SampleController { @RequestMapping(method = RequestMethod.GET) public String getCreateForm(Model model) { model.addAttribute("form", new SubAForm()); return "sample/input"; } @RequestMapping(method = RequestMethod.POST) public String register(@ModelAttribute("form") SuperForm form, Model model) { return "sample/input"; } } ------------------------------------------------------- public class SuperForm { private Long superId; public Long getSuperId() { return superId; } public void setSuperId(Long superId) { this.superId = superId; } } ------------------------------------------------------- public class SubAForm extends SuperForm { private Long subAId; public Long getSubAId() { return subAId; } public void setSubAId(Long subAId) { this.subAId = subAId; } } ------------------------------------------------------- <form:form modelAttribute="form" method="post"> <fieldset> <legend>SUPER FIELD</legend> <p> SUPER ID:<form:input path="superId" /> </p> </fieldset> <fieldset> <legend>SUB A FIELD</legend> <p> SUB A ID:<form:input path="subAId" /> </p> </fieldset> <p> <input type="submit" value="register" /> </p> </form:form>

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