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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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• Generic object load function for scala

  - by Isaac Oates

  I'm starting on a Scala application which uses Hibernate (JPA) on the back end. In order to load an object, I use this line of code: val addr = s.load(classOf[Address], addr_id).asInstanceOf[Address]; Needless to say, that's a little painful. I wrote a helper class which looks like this: import org.hibernate.Session class DataLoader(s: Session) { def loadAddress(id: Long): Address = { return s.load(classOf[Address], id).asInstanceOf[Address]; } ... } So, now I can do this: val dl = new DataLoader(s) val addr = dl loadAddress(addr_id) Here's the question: How do I write a generic parametrized method which can load any object using this same pattern? i.e val addr = dl load[Address](addr_id) (or something along those lines.) I'm new to Scala so please forgive anything here that's especially hideous.

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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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• 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 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• Generics not so generic !!

  - by Aymen

  Hi I tried to implement a generic binary search algorithm in scala. Here it is : type Ord ={ def <(x:Any):Boolean def >(x:Any):Boolean } def binSearch[T <: Ord ](x:T,start:Int,end:Int,t:Array[T]):Boolean = { if (start > end) return false val pos = (start + end ) / 2 if(t(pos)==x) true else if (t(pos) < x) binSearch(x,pos+1,end,t) else binSearch(x,start,pos-1,t) } everything is OK until I tried to actually use it (xD) : binSearch(3,0,4,Array(1,2,5,6)) the compiler is pretending that Int not a member of Ord, well what shall I do to solve this ? Thanks

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• Database structure - To join or not to join

  - by Industrial

  Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The application will be quite read-heavy and have a couple of hundred thousand rows per table. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Should we start looking at horizontal partitioning? (in conjunction with merging tables) Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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• SQL database problems with addressbook table design

  - by Sebastian Hoitz

  Hello! I am writing a addressbook module for my software right now. I have the database set up so far that it supports a very flexible address-book configuration. I can create n-entries for every type I want. Type means here data like 'email', 'address', 'telephone' etc. I have a table named 'contact_profiles'. This only has two columns: id Primary key date_created DATETIME And then there is a table called contact_attributes. This one is a little more complex: id PK #profile (Foreign key to contact_profiles.id) type VARCHAR describing the type of the entry (name, email, phone, fax, website, ...) I should probably change this to a SET later. value Text (containing the value for the attribute). I can now link to these profiles, for example from my user's table. But from here I run into problems. At the moment I would have to create a JOIN for each value that I want to retrieve. Is there a possibility to somehow create a View, that gives me a result with the type's as columns? So right now I would get something like #profile type value 1 email [email protected] 1 name Sebastian Hoitz 1 website domain.tld But it would be nice to get a result like this: #profile email name website 1 [email protected] Sebastian Hoitz domain.tld The reason I do not want to create the table layout like this initially is, that there might always be things to add and I want to be able to have multiple attributes of the same type. So do you know if there is any possibility to convert this dynamically? If you need a better description please let me know. Thank you!

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• Non Working Relationship

  - by Dominik K.

  Hello everyone, I got a problem with cake's model architecture. I got a Users-Model and a Metas-Model. Here are the model codes: Users: <?php class User extends AppModel { var $name = 'User'; var $validate = array( 'username' => array('notempty'), 'email' => array('email'), 'password' => array('notempty') ); var $displayField = 'username'; var $hasMany = array( 'Meta' => array( 'className' => 'Meta', 'foreignKey' => 'user_id' ) ); } ?> and the Metas Model: <?php class Meta extends AppModel { var $name = 'Meta'; //The Associations below have been created with all possible keys, those that are not needed can be removed var $belongsTo = array( 'User' => array( 'className' => 'User', 'foreignKey' => 'user_id', 'required' => true ) ); } ?> So now the question is why do I not get the Meta data into the User array? Should I get it in the Auth object? Or where can I work with the meta data? hope you can help me! Have a nice Day! Dom

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• How can I store in a db several phone numbers to be related to their own restaurants?

  - by Rami Alashri

  I have a table called "restaurants" which contains each restaurant information, I want to add its phone numbers. Should I make another table called say "phones" with fields "phone1", "phone2", "phone3", etc, then make a relation between them? or their is an easier way to do this? Thanks a lot :)

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• CakePHP belongsTo relationship with a variable 'model' field.

  - by gomezuk

  I've got a problem with a belongsTo relationship in CakePHP. I've got an "Action" model that uses the "actions" table and belongs to one of two other models, either "Transaction" or "Tag". The idea being that whenever a user completes a transaction or adds a tag, the action model is created to keep a log of it. I've got that part working, whenever a Transaction or Tag is saved, the aftersave() method also adds an Action record. The problem comes when I try to do a find('all') on the Action model, the related Transaction or Tag record is not being returned. actions: id model model_id created I thought I could use the "conditions" parameter in the belongsTo relationship like this: <?php class Action extends AppModel { var $name = 'Action'; var $actsAs = array('Containable'); var $belongsTo = array( 'Transaction' => array( 'foreignKey' => 'model_id', 'conditions' => array("Action.model"=>"Transaction") ), 'User' => array( 'fields' => array('User.username') ), 'Recommendation' => array( 'conditions' => array("Action.model"=>"Recommendation"), 'foreignKey' => 'model_id' ) ); } ?> But that doesn't work. Am I missing something here, are my relationships wrong (I suspect so)? After Googling this problem I cam across something called Polymorphic Behaviour but I'm not sure this will help me.

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• php doctrine relational form naming for saving data

  - by neziric

  is it possible to have an html form organized/named in such a way that $foo-fromArray($_POST) would actually save relational data as well? example: html_form_fields: user_name country_name db_table_users: id user_name db_table_countries: id country_name update: forgot to say i'm trying to make this with zend framework forms

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• To join or not to join - database structure

  - by Industrial

  Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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• Concept: Is mongo right for applying schemas?

  - by Jan

  I am currently in charge of checking wether it is valuable for one of our upcoming products to be developed on mongo. Without going too much into detail, I'll try to explain, what the app does. The app simply has "entities". These entities are technical stuff, like cell phones, TVs, Laptops, tablet pcs, and so forth. Of course, a cell phone has other attributes than a Tablet PCs and a Laptop has even other attributes, like RAM, CPU, display size and so on. Now I want to have something that we wanna call a scheme: We define that we need to have saved the display size, amount of ram size of flash devices, processor type, processor speed and so on for tablet pcs. For cell phone we might save display size, GSM, Edge, 3g, 4g, processor, ram, touch screen technology, bla bla bla. I think you got it :) What I want to realize is, that each "category" has a schema and when one of the system's users enters a new product (let's say the new iphone 4), the app constructs the form to be filled out with the appropriate attributes. So far it sounds nice and should not be a problem with mongo. But now the tough for which I could not find a clean solution.... An attribute modeled in mongo looks like: { _id: 1234456, name: "Attribute name", type: 0, "description" } But what to do, if i need this attribute in several languages, like: { en: {name: "Attribute name", type: 0, "description"}, de: {name: "Name des Attributs, type: 0, "Beschreibung"} } I also need to ensure that the german attribute gets updated as soon as the english gets updated, for instance when type changes from 0 to 1. Any ideas on that?

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