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• Rails: Generic form actions, cancel link losing `:back` on validation failure

  - by Patrick Connor

  I am trying to create a generic set of Submit, Cancel, and Destroy actions for forms. At this point, it appears that everything is working, except that I lose :back functionality then a form reloads due to validation errors. Is there a way to catch the fact that validation has failed, and in that case, keep the request.env['HTTP_REFERER'] or :back value the same without having to edit every controller? = simple_form_for @announcement do |f| = f.error_notification = f.input :message = f.input :starts_at = f.input :ends_at #submit = f.button :submit = "or " = link_to("cancel", url_for(:back)) .right - if !f.object.new_record? - resource = (f.object.class.name).downcase = link_to "destroy", url_for(:action => 'destroy'), :confirm => "Are you sure that you want to delete this #{resource}?", :method => :delete .clear .non_input #post_back_msg #indicator.inline = image_tag "indicator.gif" .inline = "Please wait..." .non_input

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• Operator as and generic classes

  - by abatishchev

  I'm writing .NET On-the-Fly compiler for CLR scripting and want execution method make generic acceptable: object Execute() { return type.InvokeMember(..); } T Execute<T>() { return Execute() as T; /* doesn't work: The type parameter 'T' cannot be used with the 'as' operator because it does not have a class type constraint nor a 'class' constraint */ // also neither typeof(T) not T.GetType(), so on are possible return (T) Execute(); // ok } But I think operator as will be very useful: if result type isn't T method will return null, instead of an exception! Is it possible to do?

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• Entity Framework: a proxy collection for displaying a subset of data

  - by Jefim

  Imagine I have an entity called Product and a repository for it: public class Product { public int Id { get; set; } public bool IsHidden { get; set; } } public class ProductRepository { public ObservableCollection<Product> AllProducts { get; set; } public ObservableCollection<Product> HiddenProducts { get; set; } } All products contains every single Product in the database, while HiddenProducts must only contain those, whose IsHidden == true. I wrote the type as ObservableCollection<Product>, but it does not have to be that. The goal is to have HiddenProducts collection be like a proxy to AllProducts with filtering capabilities and for it to refresh every time when IsHidden attribute of a Product is changed. Is there a normal way to do this? Or maybe my logic is wrong and this could be done is a better way?

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• C# Using Reflection to Get a Generic Object's (and its Nested Objects) Properties

  - by Jimbo

  This is a scenario created to help understand what Im trying to achieve. I am trying to create a method that returns the specified property of a generic object e.g. public object getValue<TModel>(TModel item, string propertyName) where TModel : class{ PropertyInfo p = typeof(TModel).GetProperty(propertyName); return p.GetValue(item, null); } The code above works fine if you're looking for a property on the TModel item e.g. string customerName = getValue<Customer>(customer, "name"); However, if you want to find out what the customer's group's name is, it becomes a problem: e.g. string customerGroupName = getValue<Customer>(customer, "Group.name"); Hoping someone can give me some insight on this way out scenario - thanks.

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• how to force nhibernate to set the foreign key of the child item?

  - by npeBeg

  i have a collection in the mapping: <bag name="Values" cascade="all-delete-orphan" lazy="false" inverse="true"> <key column="[TemplateId]"/> <one-to-many class="MyNamespace.Value, MyLib"/> </bag> the Value object has a foreign key [TemplateId]. both entities has their generator set to "identity". when i call session.Save() for the parent Template object, the Value objects has their [TemplateId] (the foreign key) set to zero, so an SQL exception appears. how do i forse nhibernate to set the FK value for the child items to the value of the inserted parent object?

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• Force freeing memory in PHP

  - by DBa

  Hi everybody, in a PHP program, I sequentially read a bunch of files (with file_get_contents), gzdecode them, json_decode the result, analyze the contents, throw the most of it away, and store about 1% in an array. Unfortunately, with each iteration (I traverse over an array containing the filenames), there seems to be some memory lost (according to memory_get_peak_usage, about 2-10 MB each time). I have double- and triplechecked my code, I am not storing unneded data in the loop (and the needed data hardly exceeds about 10MB overall), but I am frequently rewriting (actually, strings in an array). Apparently, PHP does not free the memory correctly, thus using more and more RAM until it hits the limit. Is there any way to do a forced garbage collection? Or, at least, to find out where the memory is used? Thanks in advance, Dmitri

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• How to check if TypeIdenitifier(T) is an Object?

  - by John

  I'm creating a generic list class that has a member of type Array(Array of ). The problem is the class descruction,because the class is supposed to be used for types from byte to types inheriting TObject. Specifically: destructor Destroy; var elem:T; begin /*if(T is Tobject) then //Check if T inherits TObject {Compiler error!} for elem in FData do TObject(elem).Free;*/ // do not know how to do it SetLength(FItems,0); //FItems : Array of T inherited Destroy; end; How do I check if T is TObject so I can free every member if the typeidenitifier is a class,for example?

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• WPF How to bind to a specific element in the Collection

  - by PaN1C_Showt1Me

  Hi, I want to make a binding to a specific element in the Collection. But I cannot figure out how to write the Binding. This is the code: public class MySource { .. public string SomeProp; public ICollection<T> MyCollection; .. } this.DataContext = new MySource(); <TextBox Text={Binding SomeProp} /> <TextBox Text={Binding FIRST_ELEMENT_OF_THE_MyCollection} /> <TextBox Text={Binding SECOND_ELEMENT_OF_THE_MyCollection} /> <!--Ignore other elements--> Try to replace those binding strings, please Thank you

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• Fast, cross-platform timer?

  - by dsimcha

  I'm looking to improve the D garbage collector by adding some heuristics to avoid garbage collection runs that are unlikely to result in significant freeing. One heuristic I'd like to add is that GC should not be run more than once per X amount of time (maybe once per second or so). To do this I need a timer with the following properties: It must be able to grab the correct time with minimal overhead. Calling core.stdc.time takes an amount of time roughly equivalent to a small memory allocation, so it's not a good option. Ideally, should be cross-platform (both OS and CPU), for maintenance simplicity. Super high resolution isn't terribly important. If the times are accurate to maybe 1/4 of a second, that's good enough. Must work in a multithreaded/multi-CPU context. The x86 rdtsc instruction won't work.

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• How to implement collection with covariance when delegating to another collection for storage?

  - by memelet

  I'm trying to implement a type of SortedMap with extended semantics. I'm trying to delegate to SortedMap as the storage but can't get around the variance constraints: class IntervalMap[A, +B](implicit val ordering: Ordering[A]) //extends ... { var underlying = SortedMap.empty[A, List[B]] } Here is the error I get. I understand why I get the error (I understand variance). What I don't get is how to implement this type of delegation. And yes, the covariance on B is required. error: covariant type B occurs in contravariant position in type scala.collection.immutable.SortedMap[A,List[B]] of parameter of setter underlying_=

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• on page load clone first image from collection of photos

  - by user313378

  On my page I'm getting collection of photos, and I store them as thumbs below showImage div which needs to be refreshed with cloned image onclick. Basically everything is ok except I need to populate this showImage div onpage load with first image, and then to use this onclick clone which already works. <a href="/Property/GetImage/someIntId"> <img id="someIntId" class="details" width="100" height="100" src="/Property/GetImage/7" alt=""> </a> function onPopUp() { $(".details").click(function (event) { //clone the clicked image var clone = $(this).clone(); clone.height("250px").width("280px"); //place it in the placeholder $('div#showImage').html(clone); }); }

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• Getting a java collection of objects in Alphabetical order

  - by MichaelMcCabe

  I have a question that I dont really know where to start. So I thought i'd ask it here. Basically, I have a drop down with names in it. I want these names to be in alphabetical order. Populating the drop down happens as follows; I query a database and pull down an Id and Name, make a object called "UserList", and set the name and id variables with what I get back. I then add this object to an ArrayList. I do this over and over. I then convert this collection to an array, and pass it to my JSP page using session.setAttribute("userList", UserList); I then populate the drop down as below. <c:forEach items="${usersCompanysList}" var="c" > There probably is a simple answer but how to I sort these names?

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• Determining whether a class implements a generic list in a T4 template

  - by James Hollingworth

  I'm writing a T4 template which loads some classes from an assembly, does some analysis of the classes and then generates some code. One particular bit of analysis I need to do is to determine whether the class implements a generic list. I can do this pretty simply in C#, e.g. public class Foo : List<string> { } var t = typeof(Foo); if (t.BaseType != null && t.BaseType.IsGenericType && t.BaseType.GetGenericTypeDefinition() == typeof(List<>))) Console.WriteLine("Win"); However T4 templates use the FXCop introspection engine and so you do not have access to the .net reflection API. I've spent the past couple of hours in Reflector but still can't figure it out. Does anyone have any clues about how to do this?

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• Catch a generic exception in Java?

  - by Alex Baranosky

  We use JUnit 3 at work and there is no ExpectedException annotation. I wanted to add a utility to our code to wrap this: try { someCode(); fail("some error message"); } catch (SomeSpecificExceptionType ex) { } So I tried this: public static class ExpectedExceptionUtility { public static <T extends Exception> void checkForExpectedException(String message, ExpectedExceptionBlock<T> block) { try { block.exceptionThrowingCode(); fail(message); } catch (T ex) { } } } However, Java cannot use generic exception types in a catch block, I think. How can I do something like this, working around the Java limitation? Is there a way to check that the ex variable is of type T?

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• Java generics: actual class as a generic parameter.

  - by user554916

  What do I write instead of "TheClass" to make this work? Or is there an alternative way to do it (possibly without making WithName and WithAge generic)? class Item { NeigborList<TheClass> neighbors; } class WithName extends Item { // here I want neighbors to be a NeighborList<WithName> String name; void someMethod() { System.out.println(neighbors.nearestTo(this).name); } } class WithAge extends Item { // here I want neighbors to be a NeighborList<WithAge> int age; void someOtherMethod() { System.out.println(neighbors.nearestTo(this).age); } }

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• Common type for generic classes of different types

  - by DinGODzilla

  I have (for example) Dictionary of different generic types (d1, d2, d3, d4) and I want to store them in something var d1 = new Dictionary<int, string>(); var d2 = new Dictionary<int, long>(); var d3 = new Dictionary<DateTime, bool>(); var d4 = new Dictionary<string, object>(); var something = ??? //new List<object> {d1, d2, d3, d4}; Is there any other way how to store that in something with common denominator different than object? Thanks :-)

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• Generic class implementing interface fails

  - by Pitming

  A meet a strange problem at compimation saying that a class does not implement an interface. Lets say a v got a class: public Class MyClass { ... } And an interace: public Interface IMyInterface { MyClass PropertyOfMyClass {get;} } and now a generic class: public class MyGeneric<T> where T:MyClass { T PropertyOfMyClass { get{return ...;} } } Until here everythings fine and compiles right. But this will break at compilation time: public class MyGeneric<T>:IMyInterace where T:MyClass { T PropertyOfMyClass { get{return ...;} } } Saying that MyGeneric does not implements method of IMyInterface. But obviously it does, not ?

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• Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

  - by pinkeen

  I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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• Is map/collection order stable between calls?

  - by John

  If I have a hash map and iterate over the objects repeatedly, is it correct that I'm not guaranteed the same order for every call? For example, could the following print two lines that differ from each other: Map<String,Integer> map = new HashMap<String,Integer>() {{ put("a", 1); put("b", 2); put("c", 3); }}; System.out.println(map); System.out.println(map); And is this the case for sets and collections in general? If so, what's the best way in case you have to iterate twice over the same collection in the same order (regardless of what order that is)? I guess converting to a list.

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• Generic SQL builder .NET

  - by Patrick

  I'm looking for a way to write an SQL statement in C# targeting different providers. A typical example of SQL statements differentiating is the LIMIT in PostgreSQL vs. TOP in MSSQL. Is the only way to solve SQL-syntax like the two above to write if-statements depending on which provider the user selects or using try catch statements as flow control (LIMIT didn't work, I'll try TOP instead)? I've seen the LINQ Take method, but I'm wondering if one can do this without LINQ? In other words, does C# have some generic SQL Provider class that I have failed to find that can be used?

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• .NET Garbage Collection behavior (with DataTable)

  - by gmac

  I am wonder why after creating a very simple DataTable and then setting it to null why Garbage Collection does not clear out all the memory used by that DataTable. Here is an example. The variable Before should be equal to Removed but it is not. { long Before = 0, After = 0, Removed = 0, Collected = 0; Before = GC.GetTotalMemory(true); DataTable dt = GetSomeDataTableFromSql(); After = GC.GetTotalMemory(true); dt = null; Removed = GC.GetTotalMemory(true); GC.Collect(); Collected = GC.GetTotalMemory(true); } Gives the following results. Before = 388116 After = 731248 Removed = 530176 Collected = 530176

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• Solution to compiler warning for generic varargs

  - by TJR

  A puzzle from this blog. Similar to SO1445233. Given the following source listing, explain why the compiler is producing a warning at invocation to the list method and give a solution for removing the warning without resorting to @SuppressWarnings annotation. public class JavaLanguagePuzzle3 { public static void main(String[] args) { list("1", 2, new BigDecimal("3.5")); } private static <T> List<T> list(T... items) { return Arrays.asList(items); } } Warning: Type safety: A generic array of Object&Serializable&Comparable<?> is created for a varargs parameter

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• Operation Problems in Java Generic

  - by alantheweasel

  I got some problem when i was learning Java Generic : interface calculator<T, R> { public void execute(T t, R r); } class executeAdd<T, R> implements calculator<T, R> { private T first; private R second; public executeAdd(T first, R second) { super(); this.first = first; this.second = second; } @Override public void execute(T t, R r) { // TODO Auto-generated method stub Object o = t + r // ERROR ! What i could do it ? } }

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• A generic Find method to search by Guid type for class implementing IDbSet interface

  - by imak

  I am implementing a FakeDataSet class by implementing IDbSet interface. As part of implementing this interface, I have to implement Find method. All my entity classes has an Guid type Id column. I am trying to implement Find method for this FakeDbSet class but having hard time to write it in a generic way. Below is my attempts for writing this method but since it does not know about Id been Guid type, I am getting compilation error on m.Id call. Any ideas on how this could be accomplished? public class FakeDataSet<T> : IDbSet<T> where T: class, new() { // Other methods for implementing IDbSet interface public T Find(params object[] keyValues) { var keyValue = (Guid)keyValues.FirstOrDefault(); return this.SingleOrDefault(m => m.Id == keyValue); // How can I write this } }

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• Generic arrays of parametrized ArrayLists in java?

  - by athena123

  I am new to Java, so I am not aware of the nitty gritties. Why can't I create generic array of parametrized ArrayList? Instead I have to write, ArrayList<String>[] alist = new ArrayList[10]; or I have to create List of ArrayLists. Aren't arrays supposed to be more efficient than ArrayLists? Then why doesn't Java allow it? Also, what is the difference between following two lines. ArrayList<String>[] alist = new ArrayList[10]; ArrayList<String>[] alist = new ArrayList<?>[10];

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