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  • Nested Select in Rails

    - by James
    I am working on a Rails application which uses categories for items. My category model is self-joined so that categories can be nested: class Category < ActiveRecord::Base has_many :items # Self Join (categories can have subcategories) has_many :subcategories, :class_name => "Category", :foreign_key => "parent_id" belongs_to :parent, :class_name => "Category" ... end I have a form which allows a user to create an item which currently lists all categories in a select, but they are all listed together: <%= f.label :category_id %> <%= select :item, :category_id, Category.all.collect {|c| [ c.title, c.id ]} %> So the select looks something like this: Category1 Category2 Category3BelongsTo2 Category4BelongsTo1 But what I want is: Category1 - Category4BelongsTo1 Category2 - Category3BelongsTo2 Is there a helper for this (which would be awesome!)? If not, how could I accomplish this? Thanks!

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  • Pass in the object a java class is embedded in as a parameter.

    - by Leif Andersen
    I'm building an android application, which has a list view, and in the list view, a click listener, containing an onItemClick method. So I have something like this: public class myList extends ListActivity { @Override public void onCreate(Bundle savedInstanceState) { getListView().setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { /* Do something*/ } } } Normally, this works fine. However, many times I find myself needing too preform an application using the outer class as a context. thusfar, I've used: parent.getContext(); to do this, but I would like to know, is that a bad idea? I can't really call: super because it's not really a subclass, just an embedded one. So is there any better way, or is that considered cosure? Also, if it is the right way, what should I do if the embedded method doesn't have a parameter to get the outside class? Thank you.

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  • Best way to bind node collection to itemscontrol in Silverilght

    - by mrtrombone
    I have a Silverlight project where the main objects are just a bunch of nodes that are joined to each other. A parent node can have many children. I want to be able to bind the nodes to an itemscontrol or similar and so was wondering how to best structure the parent child relationship. Is it OK to create a flat top level list of all nodes (List allNodes) and add each node to that, binding the list to the itemscontrol, then on top of that add each node to it's parent's 'childnodes' list to establish the structure - or am I doing some kind of ugly doubling up? Just hoping there is some kind of best practice or pattern I can latch on to Thanks

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  • correct way to store an exception in a variable

    - by Evan Teran
    I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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  • Creating compound applications in Windows 7

    - by Mmarquee
    I need to port a suite of Windows applications (running under XP with little security turned on) to Windows 7 with various levels of security, depending on how our clients may configure it. Each functional area is a seperate executable or DLL that is downloaded and registered by a central 'compound' application. This means that the different parts are all joined together to form in effect a large single application. My problem is that the compound application knows about the other applications via COM registery, either as a typelibrary or as OCXs, where appropriate. I have tried several questions here to try and solve the problems I am getting, but I don't seem to be able to get around the problem of needing elevated access to register applications and access the registry. Our clients will be expecting the same (relatively) seemless download and activation process as current under XP. So does anyone have a solution for registering typelibraries and OCX controls without need to go through an elevation process. Thanks in advance

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  • Ruby on Rails: Unit Testing non activerecord models and still load fixtures

    - by Vaibhav Gumashta
    I may be missing something but I am stuck in this scenario: I have a non activerecord model, which I want to test. I have derived its test case class from: Test::Unit::TestCase. However, the test case class for the model, uses within itself, other activerecord model classes and I want to load fixtures for them. My problem is that the fixtures class method is available only when I subclass the test case class from ActiveSupport::TestCase (it is defined within ActiveRecord::TestFixtures which gets included in ActiveSupport::TestCase). Any help, coz running the tests gives me the error: undefined method "fixtures" (which is understandable) and in case I derive my test case class from ActiveSupport::TestCase it complains that there is no corresponding DB table. Also, I don't want to create a dummy table for backing my model class. Thanks a ton!

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  • Get touches from UIScrollView

    - by Peter Lapisu
    Basically i want to subclass UIScrollView and hande the touches, however, the touch methods dont get called (i searched the web for a solution and i found out people pointing to override the hit test, what i did, but with no result :( ) .h @interface XScroller : UIScrollView @end .m - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event { UIView *result = nil; for (UIView *child in self.subviews) { if ([child pointInside:point withEvent:event]) { if ((result = [child hitTest:point withEvent:event]) != nil) { break; } } } return result; } - (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"BEGAN"); [super touchesBegan:touches withEvent:event]; } - (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"MOVED"); [super touchesMoved:touches withEvent:event]; } - (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"ENDED"); [super touchesEnded:touches withEvent:event]; } - (void) touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"CANCELED"); [super touchesCancelled:touches withEvent:event]; } none of the - (void) touches* methods get called, the scrolling works ok

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  • Use where condition with unjoined table

    - by Dragos D
    I have the following problem: I am trying to retreive a sum value based on one condition. Problem is that I can't join the conditional value since my tables aren't joined. Here is my syntax: SELECT SUM(value) FROM value v join day d on v.day_id = d.day_id join budget b on d.budget_id = b.budget_id join unit u on v.unit_id = u.unit_id where #output.class = (SELECT distinct s.class FROM sale s where s.id = #output.sale_id) AND u.unit_name in ('electronics') With this sybtax I get no error but neither values. Can you please tell me where I do wrong?

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  • Table-per-type inheritance insert problem

    - by gzak
    I followed this article on making a table-per-type inheritance model for my entities, but I get the following error when I try to add an instance of a subclass to the database. Here is how I create the subtype: var cust = db.Users.CreateObject<Customer>(); // Customer inherits User db.Users.AddObject(cust); db.SaveChanges(); I get the following error when I make that last call: "A value shared across entities or associations is generated in more than one location. Check that mapping does not split an EntityKey to multiple store-generated columns." With the following inner exception: "An item with the same key has already been added." Any ideas on what I could be missing?

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  • Zend_Form and Liskov Substitution Principle

    - by blockhead
    A very common pattern I see (I'm picking on Zend Framework, only because I was dealing with it at the moment of this question), is something like this: class My_Form extends Zend_Form { public function init() { $this->addElement(); } } Zend_Form is not an abstract class, but is perfectly usable on its own. This seems to be "recommended" as place to "encapsulate" your forms into a nice class. Does this violate the Liskov Substitution Principle? Each subclass of Zend_Form will have a wildy different behavior than the base class. Would it be better to use composition for this, or am I totally misunderstanding this principle?

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  • Style question: Writing "this." before instance variable and methods: good or bad idea?

    - by Uri
    One of my nasty (?) programming habits in C++ and Java is to always precede calls or accesses to members with a this. For example: this.process(this.event). A few of my students commented on this, and I'm wondering if I am teaching bad habits. My rationale is: 1) Makes code more readable — Easier to distinguish fields from local variables. 2) Makes it easier to distinguish standard calls from static calls (especially in Java) 3) Makes me remember that this call (unless the target is final) could end up on a different target, for example in an overriding version in a subclass. Obviously, this has zero impact on the compiled program, it's just readability. So am I making it more or less readable? Related Question Note: I turned it into a CW since there really isn't a correct answer.

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  • NSInvocation: object does not implement methodSignatureForSelector

    - by Sam V
    I have this weird crash that only happens when running the app on the device (doesn't happen in the Simulator). It seems like the problem surfaces out of nowhere, as I haven't changed anything on that particular class. I had the very same issue a few days ago, and I ended up fixing it by duplicating the class, renaming it, and changing the referenced class — I haven't changed a single bit of code. So I'm trying to understand why it's doing this. I've read somewhere that usually you get this console error when the object isn't a subclass of NSObject (but it is!). Here's the exact console error message: *** NSInvocation: warning: object 0x679e0 of class 'FFProximityPickerView' does not implement methodSignatureForSelector: -- trouble ahead *** NSInvocation: warning: object 0x679e0 of class 'FFProximityPickerView' does not implement doesNotRecognizeSelector: -- abort And then it crashes. I'd be very thankful for anyone who can help me on this.

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  • Java CRTP: Works for container but not for methods?

    - by Daniel
    I have a baseclass with a protected static ArrayList. I want to have a seperate ArrayList for each kind of subclass that extends this baseclass. This is when I applied CRTP: public class BaseExample<T> { protected static ArrayList<Integer> data = new ArrayList<Integer>(); } This works just fine. However, when I try to implement the following static method in the same base class, it doesn't adhere to CRTP: public static void clear() { data.clear(); } For example: class SubExample extends BaseExample<SubExample> { // insertion methods accessing 'data' field // these work fine :) } SubExample.clear(); // does not seem to clear data container Do I need to somehow explicitly specify T in my baseclass clear method? Note: These are all pure static classes.

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  • Should I use implicit conversions to enforce preconditions?

    - by Malvolio
    It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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  • uitextfield delegate must be file's owner?

    - by deafgreatdane
    I've seen a few references (eg here) in response to folks having trouble getting the keyboard to dismiss in iPhone that say "double check that the delegate is attached to file's owner. Is this necessarily true? Or just standard practice? Can't I have other objects in my nib, such as a subclass of UIViewController, and make connections to those as I like? I'd hate to have to route everything into the object that happens to be file owner. That said, I'm having a difficult time getting the keyboard to disappear. I know it's connected to the delegate, because I can set break points and step through the code. I can see the [theTextField resignFirstResponder] get called (and return true), but the keyboard still won't go away. Any other suggestions?

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  • FluentNhibernate dynamic runtime mappings.

    - by Paul Knopf
    I am building a framework where people will be able to save items that the created by inheriting a class of mine. I will be iterating over every type in the appdomain to find classes that I want to map to nhibernate. Every class that I find will be a subclass of the inherited type. I know how to create sub types in FluentNhibernate, but every sub type requires its own ClassMap class. Since I won't know these untill runtime, there is no way I can do that. Is there a way that I can add mappings to fluent nhibernate? Note, I know this is possible without fluent nhibernate using the Cfg class, but I don't want to manage the same code two different ways.

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  • How to animate stuff when using -drawRect: ?

    - by mystify
    I didn't use subviews but painted my things with -drawRect: inside an UIView subclass. Now I want to do some animations in there. I guess that I can't count on core animation now since I have no subviews. So how would I animate then? Would I set up a timer which fires like 30 times per second? How would I know the animation step? Would I make an ivar which counts the frame of the animation so that I can do my stuff in -drawRect as it gets called?

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  • Where to put conditionals in ANSI-syntax SQL queries

    - by RenderIn
    What's the difference between these two queries? I've been resistant to jumping on the ANSI-syntax bandwagon because I have not been able to unravel various syntactical ambiguities. Is 1) returning the product of the join and only then filtering out those joined records which have weight = 500? And is 2) filtering out those prior to the join? Is 2 bad syntax? Why might I use that? 1: SELECT SOMETHING FROM FOO INNER JOIN BAR ON FOO.NAME = BAR.NAME WHERE BAR.WEIGHT < 500 2: SELECT SOMETHING FROM FOO INNER JOIN BAR ON FOO.NAME = BAR.NAME AND BAR.WEIGHT < 500

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  • Gluing tiles together using imagemagick's montage command

    - by AP257
    This seems like it might be a reasonably common question, so I'm going to ask it using as many keywords as I can think of! I have a bunch of (well, nine) tile jpegs, with standard tile filenames. Each jpeg is 220x175 pixels: (top row) tile_1_0_0.jpg tile_1_1_0.jpg tile_1_2_0.jpg (middle row) tile_1_0_1.jpg tile_1_1_1.jpg tile_1_2_1.jpg (bottom row) tile_1_0_2.jpg tile_1_1_2.jpg tile_1_2_2.jpg How can I use imagemagick/montage to 'glue' or join them all together to make a single, coherent image? I don't want to resize them at all, so I guess the final image should be 660x525. That would be montage with no framing, shadowing, bordering, etc - just the nine original images, glued together to make a single jpeg. I know it should be something along these lines, but I'm struggling with getting the order and sizing right: montage +frame +shadow +label -tile 3x3 -geometry <options> *.jpg joined.jpg

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  • SQL join from multiple tables

    - by Kenny Anderson
    Hi all We've got a system (MS SQL 2008 R2-based) that has a number of "input" database and a one "output" database. I'd like to write a query that will read from the output DB, and JOIN it to data in one of the source DB. However, the source table may be one or more individual tables :( The name of the source DB is included in the output DB; ideally, I'd like to do something like the following (pseudo-SQL ahoy) SELECT output.UID, output.description, input.data from output.dbo.description LEFT JOIN (SELECT input.UID, input.data FROM [output.sourcedb].dbo.datatable ) AS input ON input.UID=output.UID Is there any way to do something like the above - "dynamically" specify the database and table to be joined on for each row in the query?

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  • Attaching files to WCF REST service responses

    - by David Seiler
    I have a resource that looks something like this: /users/{id}/summary?format={format} When format is "xml" or "json" I respond with a user summary object that gets automagically encoded by WCF - fine so far. But when format equals "pdf", I want my response to consist of a trivial HTTP response body and a PDF file attachment. How is this done? Hacking on WebOperationContext.Current.OutgoingResponse doesn't seem to work, and wouldn't be the right thing even if it did. Including the bits of the file in a CDATA section or something in the response isn't safe. Should I create a subclass of Message, then provide a custom IDispatchMessageFormatter that responds with it? I went a short distance down that path but ultimately found the documentation opaque. What's the right thing?

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  • Best practice to pass a value from pop up control on iPad.

    - by Tattat
    It is an iPad app based on SDK 3.2. I have a MainUIView, that is subclass from UIView, it have a UIButton and a UILabel. When user press the UIButton, the pop up control will be appeared with a table view. When the user select a cell from the table view, the UILabel changes content base on the user click, and the pop up table view will disappear. The question is, how can I pass the "selected cell" to the UILabel. I am thinking making a "middle man" object. When the user click the UIButton, and the "middle man" will pass to the table. When the cell is selected, the "middle man" will store the idx, and call the UILabel change content from the value of "middle man". But I think it is pretty complex to implement, is there any easier way to implement it? thz u.

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  • How to Initialise a static Map in Java

    - by fahdshariff
    How would you initialise a static Map in Java? Method one: Static initialiser Method two: instance initialiser (anonymous subclass) or some other method? What are the pros and cons of each? Here is an example illustrating two methods: import java.util.HashMap; import java.util.Map; public class Test { private static final Map<Integer, String> myMap = new HashMap<Integer, String>(); static { myMap.put(1, "one"); myMap.put(2, "two"); } private static final Map<Integer, String> myMap2 = new HashMap<Integer, String>(){ { put(1, "one"); put(2, "two"); } }; }

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  • Why does UITableViewCell have a contentView property?

    - by mystify
    What's the point of this contentView property? I mean: Why aren't all the subviews just added to self? Let me get that right: Every cell is a view (UITabvleViewCell is a UIView subclass). And this fat view has another fat view with same bounds sitting on top of it, called contentView. That contentView then carries all those other subviews. Now why didn't they save that extra chunk of memory? Is there any genius logic behind this decision? Would love to understand the reason for this.

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  • What we call this kind of chaining in C#

    - by Thinking
    Can you please tell me what kind of construct in C# is this. Code Golf: Numeric equivalent of an Excel column name C.WriteLine(C.ReadLine() .Reverse() .Select((c, i) => (c - 64) * System.Math.Pow(26, i)) .Sum()); Though I am new to C# (only two months exp so far), but since the time I have joined a C# team, I have never seen this kind of chaining. It really attracted me and I want to learn more about it. Please give some insight about this.

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