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  • Rails 3 find all associated records has_many :through

    - by Sergey
    I would like to list all posts that are connected with some specific category. I have: class Post < ActiveRecord::Base has_many :category_posts has_many :categories, :through => :category_posts end class Category < ActiveRecord::Base has_many :category_posts has_many :posts, :through => :category_posts end class CategoryPost < ActiveRecord::Base belongs_to :category belongs_to :post end And I wanna do something like this Post.where(["category.id = ?", params[:category_id]]) It indeed is very simple task, but I don't know what I should be looking for (keywords). It's the same problem like this, but in rails.

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  • How to call same method for a list of objects?

    - by Dmitry
    Suppose code like this: class Base: def start(self): pass def stop(self) pass class A(Base): def start(self): ... do something for A def stop(self) .... do something for A class B(Base): def start(self): def stop(self): a1 = A(); a2 = A() b1 = B(); b2 = B() all = [a1, b1, b2, a2,.....] Now I want to call methods start and stop (maybe also others) for each object in the list all. Is there any elegant way for doing this except of writing a bunch of functions like def start_all(all): for item in all: item.start() def stop_all(all): .....

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  • django form ModelChoiceField loads all state names while needed states which are mapped with current selected country

    - by Sonu
    I am using modelChoiceField to display country and state into address form class StateSelectionwidget(forms.Select): """ custom widget to state selection""" class Media: js = ('media/javascript/public/jquery-1.5.2.min.js', 'media/javascript/public/countrystateselection.js', ) class AddressForm(forms.Form): name = forms.CharField(max_length=30) country = forms.ModelChoiceField(queryset=[]) state = forms.ModelChoiceField(CountryState.objects, widget=StateSelectionwidget) def __init__(self, *args, **kwargs): super(AddressForm, self).__init__(*args, **kwargs) self.fields['country'].queryset = Country.objects.all() Country model is used to store country names. CountryState model is used to store all states which is foreign key to Country model At the time of form loading i am getting all state names in dropdown while i want field to be blank by default. If name field is empty at the time of form save i am getting error that name can not be empty but also getting all states into dropdown list while i want only the states which are mapped with current selected country.

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  • Multi-threaded downloader in C# question

    - by blez
    Currently I have multi-threaded downloader class that uses HttpWebRequest/Response. All works fine, it's super fast, BUT.. the problem is that the data needs to be streamed while it's downloading to another app. That means that it must be streamed in the right order, the first chunk first, and then the next in the queue. Currently my downloader class is sync and Download() returns byte[]. In my async multi-threaded class I make for example, list with 4 empty elements (for slots) and I pass each index of the slot to each thread using the Download() function. That simulates synchronization, but that's not what I need. How should I do the queue thing, to make sure the data is streamed as soon as the first chunk start downloading.

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  • FindBugs and CheckForNull on classes vs. interfaces

    - by ndn
    Is there any way to let FindBugs check and warn me if a CheckForNull annotation is present on the implementation of a method in a class, but not on the declaration of the method in the interface? import javax.annotation.CheckForNull; interface Foo { public String getBar(); } class FooImpl implements Foo { @CheckForNull @Override public String getBar() { return null; } } public class FindBugsDemo { public static void main(String[] args) { Foo foo = new FooImpl(); System.out.println(foo.getBar().length()); } } I just discovered a bug in my application due to a missing null check that was not spotted by FindBugs because CheckForNull was only present on FooImpl, but not on Foo, and I don't want to spot all other locations of this problem manually.

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  • Simple Scala syntax - trying to define "==" operator - what am I missing?

    - by Alex R
    While experimenting with some stuff on the REPL, I got to a point where I needed something like this: scala class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } Just a simple class with an "==" operator. Why doesn't it work??? Here's the result: :10: error: type mismatch; found : A required: ?{val x: ?} Note that implicit conversions are not applicable because they are ambiguous: both method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A] and method any2Ensuring in object Predef of type [A](x: A)Ensuring[A] are possible conversion functions from A to ?{val x: ?} class A(x:Int) { println(x); def ==(a:A) : Boolean = { this.x == a.x; } } ^ This is scala 2.8 RC1. Thanks

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  • Showing current value in DB in a drop down box

    - by user195257
    Hello, this is my code which populates a drop down menu, all working perfectly, but when editing a database record, i want the first value in the drop down to be what is currently in the database, how would i do this? <li class="odd"><label class="field-title">Background <em>*</em>:</label> <label><select class="txtbox-middle" name="background" /> <?php $bgResult = mysql_query("SELECT * FROM `backgrounds`"); while($bgRow = mysql_fetch_array($bgResult)){ echo '<option value="'.$bgRow['name'].'">'.$bgRow['name'].'</option>'; } ?> </select></li>

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  • How to get this to compile?

    - by ShaChris23
    I have this code which compiles and works as expected: class Right {}; class Left { public: Left& operator = (Right const&) { //... Do something ... return *this; } }; int main() { Right right; Left left; // Assign individual object -- this works left = right; } But now, this one surprises me, I thought the template would work itself out since I already provided the = operator() to the Left class. int main() { ... std::list<Right> rightLst; std::list<Left> leftLst; // Assign a list of objects -- this doesn't compile leftLst = rightLst; } What can I do so that I could convert the rightLst to leftLst conversion in a single line?

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  • Any way to set or overwrite the __line__ and __file__ metadata?

    - by charles.merriam
    I'm writing some code that needs to change function signatures. Right now, I'm using Simionato's FunctionMaker class, which uses the (hacky) inspect module, and does a compile. Unfortunately, this still loses the line and file metadata. Does anyone know: If it is possible to overwrite these values in some odd way? If hacking up a class with a complex getattribute() to intercept the values and also try to make the class looks like a function is any more possible than a moose with a flying nun hat? Is there an alternative to the (hacky) inspect module? PEP 362 is dead dead dead? I know decorators and cPickle users fight with this. What other situations is the read only metadata in people's way? I appreciate any insights. Thank you.

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  • Django admin page dropdowns

    - by zen
    I am building a high school team application using Django. Here is my working models file: class Directory(models.Model): school = models.CharField(max_length=60) website = models.URLField() district = models.SmallIntegerField() conference = models.ForeignKey(Conference) class Conference(models.Model): conference_name = models.CharField(max_length=50) url = models.URLField() class Meta: ordering = ['conference_name'] When I open my admin pages and go to edit a school's conference the drop down looks like this: <select> <option value="1">Conference Object</option> <option value="2">Conference Object</option> <select> How do I replace "Conference Object" with the conference_name?

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  • Opening IProject properties when another (adaptable to IProject) object is selected

    - by Stan
    I have a custom view displaying a hierarchy model of the current project. The root element is of class MyProject which is my own class, but it represents one Eclipse IProject, and it's adaptable to IProject. I have a "properties" menu option in the popup menu for that view, and I'd like to open up IProject's properties when a MyProject object is selected. PropertyDialogAction only looks for property pages registered for MyProject and doesn't give me a chance to offer an adapter -- or, at least, I don't know how to offer one. What's the proper solution for this? In the meantime, I've overridden PropertyDialogAction to handle my class in the special way I require, but that seems like quite a kludge to get this done.

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  • Can I improve performance by refactoring SQL commands into classes?

    - by Matthew Jones
    Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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  • Can I improve performance by refactoring SQL commands into C# classes?

    - by Matthew Jones
    Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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  • Wrapping Multiple Elements (jQuery)

    - by Nimbuz
    I've this piece of HTML: div.content div.one content div.two content div.three content I want to add two divs on top and bottom and wrap one div around it so it becomes: div.top div.wrapper div.content div.one content div.two content div.three content div.bottom I'm aware of the several wrap selectors (innerWrap, wrapAll etc..) but I'm not sure how to wrap 2 divs. The following jQuery might work, but is there a better way to write it? $('content').wrap('<div class="wrapper"></div'); $('.wrapper').before('<div class="top"></div>'); $('.wrapper').after('<div class="bottom"></div>');

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  • In c++ is there any Events/delegates/interfaces/notifications! anything?

    - by Bach
    Say i have these classes ViewA and ViewB In objective C using the delegate pattern I could do @protocol ViewBDelegate{ - (void) doSomething(); } then in ViewB interface: id<ViewBDelegate> delegate; then in ViewA implementation i set the delegate: viewB.delegate = self; and now I can call in doSomething from viewB onto any that unknown type delegate. [delegate doSomething]; "C++ How to Program" has been the worse read an can't find simple examples that demonstrates basic design patterns. What i'm looking for in C++ is: events ActionScript and java either delegates or notifications in Objective C anything that allows class A, Class B and Class C to know that ClassX didSomething()!!! thanks

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  • How binding each column to other data source..

    - by liran
    hello, i have datagridview and Object data source : public class Data { public general general { get; set; } public Person Person { get; set; } } public class general { public int Id { get; set; } public int Name { get; set; } } public class Person { public int Tag { get; set;} } } i want to bind first column to general.id and second to person.Tag, how i do this, its is possible to bind each column to other dataSource without add any code in data, person or general classes. maybe need to add column manually? Thanks

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  • Need to create a string token dynamically base on which method is calling it

    - by sa
    This is a minimal code. I have the string Str which is used by various methods. I want to in getId method be able to do 2 things Assign class="PDP" to it and Give it a value3 So the final string looks like <tr class='PDP' id='{2}'> <td {0}</td><td>{1}</td></tr> But please note that I will need different values for class in different methods so some Str will have PDP, another will have PTM etc. Is there a clean way to achieve this . private const string Str = "<tr><td >{0}</td><td>{1}</td></tr>"; public static string getId() { string field=string.Format(str, value1,value2, found=true? value3:""); }

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • C++, create an instance from a static method

    - by Manux
    Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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  • Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

    - by Shane MacLaughlin
    Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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  • Constructor with non-instance variable assistant?

    - by Robert Fischer
    I have a number of classes that look like this: class Foo(val:BasicData) extends Bar(val) { val helper = new Helper(val) val derived1 = helper.getDerived1Value() val derived2 = helper.getDerived2Value() } ...except that I don't want to hold onto an instance of "helper" beyond the end of the constructor. In Java, I'd do something like this: public class Foo { final Derived derived1, derived2; public Foo(BasicData val) { Helper helper = new Helper(val); derived1 = helper.getDerived1Value(); derived2 = helper.getDerived2Value(); } } So how do I do something like that in Scala? I'm aware of creating a helper object of the same name of the class with an apply method: I was hoping for something slightly more succinct.

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  • How to get global access to enum types in C#?

    - by lala
    This is probably a stupid question, but I can't seem to do it. I want to set up some enums in one class like this: public enum Direction { north, east, south, west }; Then have that enum type accessible to all classes so that some other class could for instance have: Direction dir = north; and be able to pass the enum type between classes: public void changeDirection(Direction direction) { dir = direction; } I thought that setting the enum to public would make this automatically possible, but it doesn't seem to be visible outside of the class I declared the enum in.

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  • Can't get images to go under each other

    - by Thomas Pen
    ello I'm new to html and css and tried to display a images that are floating right. Now I want to get the images under each other but is doesn't work. Can someone help me? this my css code for the images: .imagesLeft{ float: left; margin: 5px; } .imagesRight{ float: right; margin: 5px; } this my html code for the images: <div class="imagesRight"> <img src="../images/medewerkers.jpg"> </div> <div class="imagesRight"> <img src="../images/medewerkers1.jpg"> </div> <div class="imagesRight"> <img src="../images/medewerkers2.jpg"> </div> Thanks in advance !

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  • Does AsEnumerable() cache all result (LINQ)

    - by Akshay
    When we call a query operator on a sequence, a sequence-specific operator gets called. I mean if i call Where<>() operator on IEnumerable<>, the operator that will be called will be defined in Enumerable class and if it's called on IQueryable<>, the one defined in Queryable class will be called. Consider the operator Reverse, defined in the Enumerable class. If i want to call it on Iqueryable<> then I must use the AsEnumerable<>() operator to first convert it into IEnumerable<>. db.Countries.OrderBy(cntry=>cntry.CountryName).AsEnumerable().Reverse() But the Reverse operator got to have all records at the same time so that it can reverse them. In the above code do all the records get loaded in memory first and then the Reverse() operator is reversing it ?

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