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  • Linq to sql DataContext cannot set load options after results been returned

    - by David Liddle
    I have two tables A and B with a one-to-many relationship respectively. On some pages I would like to get a list of A objects only. On other pages I would like to load A with objects in B attached. This can be handled by setting the load options DataLoadOptions options = new DataLoadOptions(); options.LoadWith<A>(a => a.B); dataContext.LoadOptions = options; The trouble occurs when I first of all view all A's with load options, then go to edit a single A (do not use load options), and after edit return to the previous page. I understand why the error is occurring but not sure how to best get round this problem. I would like the DataContext to be loaded up per request. I thought I was achieving this by using StructureMap to load up my DataContext on a per request basis. This is all part of an n-tier application where my Controllers call Services which in turn call Repositories. ForRequestedType<MyDataContext>() .CacheBy(InstanceScope.PerRequest) .TheDefault.Is.Object(new MyDataContext()); ForRequestedType<IAService>() .TheDefault.Is.OfConcreteType<AService>(); ForRequestedType<IARepository>() .TheDefault.Is.OfConcreteType<ARepository>(); Here is a brief outline of my Repository public class ARepository : IARepository { private MyDataContext db; public ARepository(MyDataContext context) { db = context; } public void SetLoadOptions(DataLoadOptions options) { db.LoadOptions = options; } public IQueryable<A> Get() { return from a in db.A select a; } So my ServiceLayer, on View All, sets the load options and then gets all A's. On editing A my ServiceLayer should spin up a new DataContext and just fetch a list of A's. When sql profiling, I can see that when I go to the Edit page it is requesting A with B objects.

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  • nhibernate many to many deletes

    - by asi farran
    I have 2 classes that have a many to many relationship. What i'd like to happen is that whenever i delete one side ONLY the association records will be deleted with no concern which side i delete. simplified model: classes: class Qualification { IList<ProfessionalListing> ProfessionalListings } class ProfessionalListing { IList<Qualification> Qualifications void AddQualification(Qualification qualification) { Qualifications.Add(qualification); qualification.ProfessionalListings.Add(this); } } fluent automapping with overrides: void Override(AutoMapping<Qualification> mapping) { mapping.HasManyToMany(x => x.ProfessionalListings).Inverse(); } void Override(AutoMapping<ProfessionalListing> mapping) { mapping.HasManyToMany(x => x.Qualifications).Not.LazyLoad(); } I'm trying various combinations of cascade and inverse settings but can never get there. If i have no cascades and no inverse i get duplicated entities in my collections. Setting inverse on one side makes the duplication go away but when i try to delete a qualification i get a 'deleted object would be re-saved by cascade'. How do i do this? Should i be responsible for clearing the associations of each object i delete?

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  • Help with editing data in entity framework.

    - by Levelbit
    Title of this question is simple because there is no an easy explanation for what I'm trying to ask you. I hope you'll understand in the end :). I have to tables in my database: Company and Location (relationship:one to many) and corresponding entity sets. In my wpf application I have some datagrid which I want to fill with locations and to be able to edit every row in separate window as some form of details view (so I don't want to edit my data in datagrid). I did this by accessing Location entity from selected row and creating a new Location entity and then I copy properties from original entity to newly created. Something like cloning the object. After editing if I press OK changed data is copied to original object back, and if I press Cancel nothing happens. Of course, you probably thinking I could use NoTracking option and AttachAsModified method as was mentioned as solution in some earlier questions(see:http://stackoverflow.com/questions/803022/changing-entities-in-the-entityframework) by Alex James, but lets say I had some problems about that and I have my own reasons for doing this. Finally, because navigation property(Company) of my location entity is assigned to newly created location object(during cloning) from some reason in object context additional object as copy of object I want to edit from datagrid is created without my will(similar problem :http://blogs.msdn.com/alexj/archive/2009/12/02/tip-47-how-fix-up-can-make-it-hard-to-change-relationships.aspx). So, when I do ObjectContext.SaveChanges it inserts additional row of data into my database table Location, the same as the one i wanted to edit. I read about sth like this, but I don't quite understand why is that and how to block or override this. I hope I was clear as I could. Please, solutions or some other ideas.

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  • Entity Framework with ASP.NET MVC. Updating entity problem

    - by Kitaly
    Hi people. I'm trying to update an entity and its related entities as well. For instance, I have a class Car with a property Category and I want to change its Category. So, I have the following methods in the Controller: public ActionResult Edit(int id) { var categories = context.Categories.ToList(); ViewData["categories"] = new SelectList(categories, "Id", "Name"); var car = context.Cars.Where(c => c.Id == id).First(); return PartialView("Form", car); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(Car car) { var category = context.Categories.Where(c => c.Id == car.Category.Id).First(); car.Category = category; context.UpdateCar(car); context.SaveChanges(); return RedirectToAction("Index"); } The UpdateCar method, in ObjectContext class, follows: public void UpdateCar(Car car) { var attachedCar = Cars.Where(c => c.Id == car.Id).First(); ApplyItemUpdates(attachedCar, car); } private void ApplyItemUpdates(EntityObject originalItem, EntityObject updatedItem) { try { ApplyPropertyChanges(originalItem.EntityKey.EntitySetName, updatedItem); ApplyReferencePropertyChanges(updatedItem, originalItem); } catch (InvalidOperationException ex) { Console.WriteLine(ex.ToString()); } } public void ApplyReferencePropertyChanges(IEntityWithRelationships newEntity, IEntityWithRelationships oldEntity) { foreach (var relatedEnd in oldEntity.RelationshipManager.GetAllRelatedEnds()) { var oldRef = relatedEnd as EntityReference; if (oldRef != null) { var newRef = newEntity.RelationshipManager.GetRelatedEnd(oldRef.RelationshipName, oldRef.TargetRoleName) as EntityReference; oldRef.EntityKey = newRef.EntityKey; } } } The problem is that when I set the Category property after the POST in my controller, the entity state changes to Added instead of remaining as Detached. How can I update one-to-one relationship with Entity Framework and ASP.NET MVC without setting all the properties, one by one like this post?

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  • Entity Framework query

    - by carter-boater
    Hi all, I have a piece of code that I don't know how to improve it. I have two entities: EntityP and EntityC. EntityP is the parent of EntityC. It is 1 to many relationship. EntityP has a property depending on a property of all its attached EntityC. I need to load a list of EntityP with the property set correctly. So I wrote a piece of code to get the EntityP List first.It's called entityP_List. Then as I wrote below, I loop through the entityP_List and for each of them, I query the database with a "any" function which will eventually be translated to "NOT EXIST" sql query. The reason I use this is that I don't want to load all the attached entityC from database to memory, because I only need the aggregation value of their property. But the problem here is, the looping will query the databae many times, for each EntityP! So I am wondering if anybody can help me improve the code to query the database only once to get all the EntityP.IsAll_C_Complete set, without load EntityC to memory. foreach(EntityP p in entityP_List) { isAnyNotComoplete = entities.entityC.Any(c => c.IsComplete==false && c.parent.ID == p.ID); p.IsAll_C_Complete = !isAnyNotComoplete; } Thank you very much!

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  • What is Adobe Flex? Is it just Flash II?

    - by Adam Davis
    Question Alright, I'm confused by all the buzzwords and press release bingo going on. What is the relationship between flash and flex: Replace flash (not really compatible) Enhance flash The next version of flash but still basically compatible Separate technology altogether ??? If I'm starting out in Flash now, should I just skip to Flex? Follow up Ok, so what I'm hearing is that there's three different parts to the puzzle: Flash The graphical editor used to make "Flash Movies", ie it's an IDE that focuses on the visual aspect of "Flash" (Officially Flash CS3?) The official name for the display plugins (ie, "Download Flash Now!") A general reference to the entire technology stack In terms of the editor, it's a linear timeline based editor, best used for animations with complex interactivity. Actionscript The "Flash" programming language Flex An Adobe Flash IDE that focuses on the coding/programming aspect of "Flash" (Flex Builder?) A Flash library that enhances Flash and makes it easier to program for (Flex SDK?) Is not bound to a timeline (as the Flash IDE is) and so "standard" applications are more easily accomplished. Is this correct?

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  • Hibernate bit array to entity mapping

    - by teabot
    I am trying to map a normalized Java model to a legacy database schema using Hibernate 3.5. One particular table encodes a foreign keys in a one-to-many relationship as a bit array column. Consider tables 'person' and 'clubs' that describes people's affiliations to clubs: person .----.------. club: .----.---------.---------------------------. | id | name | | id | name | members | binary(members) | |----+------| |----+---------|---------+-----------------| | 1 | Bob | | 10 | Cricket | 0 | 000 | | 2 | Joe | | 11 | Tennis | 5 | 101 | | 3 | Sue | | 12 | Cooking | 7 | 111 | '----'------' | 13 | Golf | 3 | 100 | '----'---------'---------'-----------------' So hopefully it is clear that person.id is used as the bit index in the bit array club.members. In this example the members column tells us that: no one is a member of Cricket, Bob/Sue - Tennis, Bob/Sue/Joe - Cooking and Sue - Golf. In my Java domain I'd like to declare this with entities like so: class Person { private int id; private String name; ... } class Club { private Set<Person> members; private int id; private String name; ... } I am assuming that I must use a UserType implementation but have been unable to find any examples where the items described by the user type are references to entities - not literal field values - or composites thereof. Additionally I am aware that I'll have to consider how the person entities are fetched when a club instance is loaded. Can anyone tell me how I can tame this legacy schema with Hibernate?

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  • Objective-C: fetchManagedObjectsForEntity problem

    - by Meko
    Hi.I am trying to get value from CoreData entity name Person with predicate and then comparing with new data in dictionary.But it it returns every time 0 .And it creates about 5 person with same name. NSPredicate *predicate = [NSPredicate predicateWithFormat:@"userName == %@",[flickr usernameForUserID:@"owner"]]; peopleList = (NSMutableArray *)[flickr fetchManagedObjectsForEntity:@"Person" withPredicate:predicate]; NSEnumerator *enumerator = [peopleList objectEnumerator]; Person *person; BOOL exists = FALSE; while (person = [enumerator nextObject]) { NSLog(@" Person is: %@ ", person.userName); NSLog(@"Person ID IS %@",person.userID); NSLog(@"Dict ID is %@",[dict objectForKey:@"owner"]); if([person.userID isEqualToString:[dict objectForKey:@"owner"]]) { exists = TRUE; NSLog(@"-- Person Exists : %@--", person.userName); [newPhoto setPerson:person]; } } Here peopleList returns 0 and the enumerator also 0 and it does not use if and not comparing.In my entity I have Person and Photo entities.In Person I have userName and userID attributes and also one-to many relationship with Photo entity. I think problem in predicate but i cant figure out it .

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  • Designing bayesian networks

    - by devoured elysium
    I have a basic question about Bayesian networks. Let's assume we have an engine, that with 1/3 probability can stop working. I'll call this variable ENGINE. If it stops working, then your car doesn't work. If the engine is working, then your car will work 99% of the time. I'll call this one CAR. Now, if your car is old(OLD), instead of not working 1/3 of the time, your engine will stop working 1/2 of the time. I'm being asked to first design the network and then assign all the conditional probabilities associated with the table. I'd say the diagram of this network would be something like OLD -> ENGINE -> CAR Now, for the conditional probabilities tables I did the following: OLD |ENGINE ------------ True | 0.50 False | 0.33 and ENGINE|CAR ------------ True | 0.99 False | 0.00 Now, I am having trouble about how to define the probabilities of OLD. In my point of view, old is not something that has a CAUSE relationship with ENGINE, I'd say it is more a characteristic of it. Maybe there is a different way to express this in the diagram? If the diagram is indeed correct, how would I go to make the tables? Thanks

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  • Trouble understanding the whole OSGi web eco system

    - by Jens
    Hello, I am pretty new to the whole Java and OSGi world and I have trouble understanding the eco system of a OSGi web application. To be more precise I am at the moment trying to understand how all the parts of the eco system are related to each other: OSGi Framework (e.g. Apache Felix, Equinox, Knoplerfish) OSGi Runtime (e.g. Spring DM Server, Pax Runner, Apache Karaf) Web Extender (e.g. Pax Web Extender, Spring Web Extender) Web Container (e.g. Apache Tomcat, Jetty) To give you a visual representation of my actual understanding of their relationship check out this image: As far as I know the OSGi Framework is a implementation of the OSGi specification. The runtime is a distribution which adds additional functionality on top of the OSGi specification like logging for instance. Since there seem to be some differences in the classpath mechanism of OSGi and web containers like Tomcat you need some kind of translator. This part is handled by the "Web Extender". Would you please clarify this whole thing for me? Am I understanding everything correct?

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  • Attributes of attributevalue element in SAML 2 Attribute Statement

    - by AJ
    I am building a web service that receives a SAML attribute query and responds with an attribute statement. I know I can return one or multiple values of a SAML attribute. I have some values that are dependent on the other attribute values. I need to show that relationship. Let us say, the query is for the Subject Dave and the return values are his company and job title. Dave can work at multiple companies with job title at each company. I have two options of sending this data back: Send this as a complextype by defining an attribute organization and return xml within that attribute. <saml:Attribute name="company"> <saml:AttributeValue> <company name="company1" jobtitle="CIO"/> <company name="company2" jobtitle="VP"/> </saml:AttributeValue> Try to send multiple values of attributes somehow sending a reference in attributevalue element. <saml:Attribute name="company"> <attributeValue>company1</attributeValue> <attributeValue>company2</attributeValue> </saml:Attribute> <saml:Attribute name="jobTitle> <attributeValue company="company1">CIO</attributeValue> <attributeValue company="company2">VP</attributeValue> </saml:Attribute> Which approach will you prefer? Why? I am biased towards second approach as it does not require client to know about any schema. It does require them to know about non-standard attribute company in the attribute value.

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  • How best to use XPath with very large XML files in .NET?

    - by glenatron
    I need to do some processing on fairly large XML files ( large here being potentially upwards of a gigabyte ) in C# including performing some complex xpath queries. The problem I have is that the standard way I would normally do this through the System.XML libraries likes to load the whole file into memory before it does anything with it, which can cause memory problems with files of this size. I don't need to be updating the files at all just reading them and querying the data contained in them. Some of the XPath queries are quite involved and go across several levels of parent-child type relationship - I'm not sure whether this will affect the ability to use a stream reader rather than loading the data into memory as a block. One way I can see of making it work is to perform the simple analysis using a stream-based approach and perhaps wrapping the XPath statements into XSLT transformations that I could run across the files afterward, although it seems a little convoluted. Alternately I know that there are some elements that the XPath queries will not run across, so I guess I could break the document up into a series of smaller fragments based on it's original tree structure, which could perhaps be small enough to process in memory without causing too much havoc. I've tried to explain my objective here so if I'm barking up totally the wrong tree in terms of general approach I'm sure you folks can set me right...

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  • MVC nhibernate entiry mapping for dropdown list

    - by Rod McLeay
    Hi, I have a dropdown list on an ASP.NET MVC project that I am pretty sure is not binding to my model because of my nhibernate mapping. I have tried many variations on the asp mvc side resulting in this post here. MVC side of things seems fine I believe the issue may be that my object is trying to bind, but my mapping is out of whack. My mapping is: <many-to-one name="Project" lazy="false" class="AgileThought.ERP.Domain.Property.Project" column="ProjectGUID" /> My View gives an error saying that the GUID from the dropdownList selected value is not valid. Which I think may be that it is trying to push the GUID into my related project object. The value 'fd38c877-706f-431d-b624-1269184eeeb5' is invalid. My related project list binds to the dropdown list just fine, it is just not binding to my models Project entity. Does the related Project entity need to know about its relationship? Its really just a lookup list. Many thanks for your time and best regards, Rod

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  • dynamic check_box using field_for in rails

    - by Craig Whitley
    I have a many-to-many relationship with a link box, and I want to pull those models together into one form so I can update from the same page. I'm really struggling with getting the check_box to even show all the elements of my array - I've scoured the net and been working on this literally all day, and I'm finding it difficult to apply the information I'm reading to my problem. I'm also extremely new to RoR and I've been following a bit of an outdated video tutorial (pre 2.0) so apologies for my code. So far, I've got it to output only one key pair in the array (the last one) - although outside the form, the code used in the tutorial works exactly how it should. Thats of little use though! Host is the model for which the main form is for, and Billing is the outside model that I'm trying to add to the form. This is the code that works outside of the form from the tutorial: <% for billing in @billings -%> <%= check_box_tag('billing_title[]', billing.id, @host.billings.collect {|obj| obj.id}.include?(billing.id))%> <%= billing.title %><br /> <% end -%> I just need to know how to make it work inside the form. This is the aforementioned code that only retrieves the last array keypair after looping through them: <% f.fields_for :billings do |obj| %><br /> <%= check_box_tag('billing_title[]', billing.id, @billings.collect {|obj| obj.id}.include?(billing.id))%> <%= billing.title %><br /> <% end %> The debug(@billings) : --- - !ruby/object:Billing attributes: title: Every Month id: "1" attributes_cache: {} - !ruby/object:Billing attributes: title: 12 Months id: "2" attributes_cache: {} - !ruby/object:Billing attributes: title: 6 Months id: "5" attributes_cache: {} Any help really appreciated.

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  • Core Data - Entity Relationships Not Working as expected

    - by slimms
    I have set up my data model in xcode like so EntityA AttA1 AttA2 EntityB AttB1 AttB2 AttB3 I then set up the relationships EntityA Name: rlpToEntityB Destination: EntityB Inverse: rlpToEntityA To Many: Checked EntityB Name: rlpToEntityA Destination: EntityA Inverse: rlpToEntityB To Many: UnChecked i.e. relationship between the two where Each one of EntityA can have many EntityB's It is my understanding that if i fetch a subset of EntityB's I can then retrieve the values for the related EntityA's. I have this working so that i can retrieve the EntityB values using NSManagedObject *objMO = [fetchedResultsController objectAtIndexPath:indexPath]; strValueFromEntityB = [objMO valueForKey:@"AttB1"]; However, if I try to retrieve a related value from EntityA by doing the following strValueFromEntityA = [objMO valueForKey:@"AttA1"]; I get the error "The entity EntityB is not Key value coding-compliant for the key Atta1" Not surprisingly i suppose if i switch things around to fetch from EntityA i cannot access attributes of EntityB So it appears the defined relationshipare being ignored. Can anyone spot what i am doing wrong? I confess im very new to iPhone programming and especially to Core Data so please go easy on me and provide verbose explanations or point me in the direction a specific resource. I have downloaded the apple sample apps (Core Data Books, Top Songs and recipes) but I still can't work this out. Thanks in advance, Nev.

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  • The type of field isn't supported by declared persistence strategy "OneToMany"

    - by Robert
    We are new to JPA and trying to setup a very simple one to many relationship where a pojo called Message can have a list of integer group id's defined by a join table called GROUP_ASSOC. Here is the DDL: CREATE TABLE "APP"."MESSAGE" ( "MESSAGE_ID" INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1) ); ALTER TABLE "APP"."MESSAGE" ADD CONSTRAINT "MESSAGE_PK" PRIMARY KEY ("MESSAGE_ID"); CREATE TABLE "APP"."GROUP_ASSOC" ( "GROUP_ID" INTEGER NOT NULL, "MESSAGE_ID" INTEGER NOT NULL ); ALTER TABLE "APP"."GROUP_ASSOC" ADD CONSTRAINT "GROUP_ASSOC_PK" PRIMARY KEY ("MESSAGE_ID", "GROUP_ID"); ALTER TABLE "APP"."GROUP_ASSOC" ADD CONSTRAINT "GROUP_ASSOC_FK" FOREIGN KEY ("MESSAGE_ID") REFERENCES "APP"."MESSAGE" ("MESSAGE_ID"); Here is the pojo: @Entity @Table(name = "MESSAGE") public class Message { @Id @Column(name = "MESSAGE_ID") @GeneratedValue(strategy = GenerationType.IDENTITY) private int messageId; @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.PERSIST) private List groupIds; public int getMessageId() { return messageId; } public void setMessageId(int messageId) { this.messageId = messageId; } public List getGroupIds() { return groupIds; } public void setGroupIds(List groupIds) { this.groupIds = groupIds; } } When we try to execute the following test code we get <openjpa-1.2.3-SNAPSHOT-r422266:907835 fatal user error> org.apache.openjpa.util.MetaDataException: The type of field "pojo.Message.groupIds" isn't supported by declared persistence strategy "OneToMany". Please choose a different strategy. Message msg = new Message(); List groups = new ArrayList(); groups.add(101); groups.add(102); EntityManager em = Persistence.createEntityManagerFactory("TestDBWeb").createEntityManager(); em.getTransaction().begin(); em.persist(msg); em.getTransaction().commit(); Help!

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  • How can I get a distinct list of elements in a hierarchical query?

    - by RenderIn
    I have a database table, with people identified by a name, a job and a city. I have a second table that contains a hierarchical representation of every job in the company in every city. Suppose I have 3 people in the people table: [name(PK),title,city] Jim, Salesman, Houston Jane, Associate Marketer, Chicago Bill, Cashier, New York And I have thousands of job type/location combinations in the job table, a sample of which follow. You can see the hierarchical relationship since parent_title is a foreign key to title: [title,city,pay,parent_title] Salesman, Houston, $50000, CEO Cashier, Houston, $25000 CEO, USA, $1000000 Associate Marketer, Chicago, $75000 Senior Marketer, Chicago, $125000 ..... The problem I'm having is that my Person table is a composite key, so I don't know how to structure the start with part of my query so that it starts with each of the three jobs in the cities I specified. I can execute three separate queries to get what I want, but this doesn't scale well. e.g.: select * from jobs start with city = (select city from people where name = 'Bill') and title = (select title from people where name = 'Bill') connect by prior parent_title = title UNION select * from jobs start with city = (select city from people where name = 'Jim') and title = (select title from people where name = 'Jim') connect by prior parent_title = title UNION select * from jobs start with city = (select city from people where name = 'Jane') and title = (select title from people where name = 'Jane') connect by prior parent_title = title How else can I get a distinct list (or I could wrap it with a distinct if not possible) of all the jobs which are above the three people I specified?

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  • JSF Managed Property question

    - by kidvid
    I have a search page that I'll called "Parent." The search page references a country lookup page that I'll call "Child." When the user selects a country on Child's page and clicks on OK, I set the country back into the parent page. I do this by calling a method on the Parent page called "UpdateCountryCodeWithLookupValue(Child child)" When the user clicks on OK on the Child page, that method gets called in the parent, wherein it'll get the selected country code out of the Child page and set it into a text entry field. My question has to do with the proper way to set up this relationship in the faces config file. The way I have it now is that the child has a managed property for the parent. I.e., in my Child page I defined a method called "SetParent(Parent parent)". Is there any drawback to doing it this way? Would it be preferable to set the managed property so that the Child page class is a property of the parent instead of vice-versa? Let's say that I could have two Parent (search) pages open at the same time, and each of these was able to open the Child page (country code lookup). What would be the ramification for that circumstance in terms of the managed property in the faces config file? Thanks, Adrian

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  • Rails Polymorphic Association with multiple associations on the same model

    - by Matt Rogish
    My question is essentially the same as this one: http://stackoverflow.com/questions/1168047/polymorphic-association-with-multiple-associations-on-the-same-model However, the proposed/accepted solution does not work, as illustrated by a commenter later. I have a Photo class that is used all over my app. A post can have a single photo. However, I want to re-use the polymorphic relationship to add a secondary photo. Before: class Photo belongs_to :attachable, :polymorphic => true end class Post has_one :photo, :as => :attachable, :dependent => :destroy end Desired: class Photo belongs_to :attachable, :polymorphic => true end class Post has_one :photo, :as => :attachable, :dependent => :destroy has_one :secondary_photo, :as => :attachable, :dependent => :destroy end However, this fails as it cannot find the class "SecondaryPhoto". Based on what I could tell from that other thread, I'd want to do: has_one :secondary_photo, :as => :attachable, :class_name => "Photo", :dependent => :destroy Except calling Post#secondary_photo simply returns the same photo that is attached via the Photo association, e.g. Post#photo === Post#secondary_photo. Looking at the SQL, it does WHERE type = "Photo" instead of, say, "SecondaryPhoto" as I'd like... Thoughts? Thanks!

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  • How do I process a nested list?

    - by ddbeck
    Suppose I have a bulleted list like this: * list item 1 * list item 2 (a parent) ** list item 3 (a child of list item 2) ** list item 4 (a child of list item 2 as well) *** list item 5 (a child of list item 4 and a grand-child of list item 2) * list item 6 I'd like to parse that into a nested list or some other data structure which makes the parent-child relationship between elements explicit (rather than depending on their contents and relative position). For example, here's a list of tuples containing an item and a list of its children (and so forth): [('list item 1',), ('list item 2', [('list item 3',), [('list item 4', [('list item 5'),]] ('list item 6',)] I've attempted to do this with plain Python and some experimentation with Pyparsing, but I'm not making progress. I'm left with two major questions: What's the strategy I need to employ to make this work? I know recursion is part of the solution, but I'm having a hard time making the connection between this and, say, a Fibonacci sequence. I'm certain I'm not the first person to have done this, but I don't know the terminology of the problem to make fruitful searches for more information on this topic. What problems are related to this so that I can learn more about solving these kinds of problems in general?

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  • Entity Framework - Foreign key constraints not added for inherited entity

    - by Tri Q
    Hello, It appears to me that a strange phenomenon is occurring with inherited entities (TPT) in EF4. I have three entities. 1. Asset 2. Property 3. Activity Property is a derived-type of Asset. Property has many activities (many-to-many) When modeling this in my EDMX, everything seems fine until I try to insert a new Property into the database. If the property does not contain any Activity, it works, but all hell breaks loose when I add some new activities to the new Property. As it turns out after 2 days of crawling the web and fiddling around, I noticed that in the EF store (SSDL) some of the constraints between entities were not picked up during the update process. Property_Activity table which links properties and activities show only one constraint FK_Property_Activity_Activity but FK_Property_Activity_Property was missing. I knew this is an Entity Framework anomoly because when I switched the relationship in the database to: Asset <-- Asset_Activity <-- Activity After an update, all foreign key constraints are picked up and the save is successful, with or without activities in the new property. Is this intended or a bug in EF? How do I get around this problem? Should I abandon inheritance altogether?

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  • How to create a view to manage associations between HABTM models? (Rails)

    - by Chris Hart
    Hello, I am using Ruby on Rails and need to create a view that allows the creation of records through a HABTM relationship to another model. Specifically, I have the following models: Customer and ServiceOverride, and a join table customers_serviceoverrides. Using the customer view for create/update, I need to be able to create, update and delete ServiceOverrides and manage the attributes of the associated model(s) from the same view. Visually I'd prefer to have something like a plus/minus sign to add/delete service overrides, and each serviceoverride record has two string entities which need to be displayed and editable as well. However, if I could just get the code (a kind of nested form, I'm assuming?) working, I could work out the UI aspects. The models are pretty simple: class ServiceOverride < ActiveRecord::Base has_and_belongs_to_many :customers end class Customer < ActiveRecord::Base has_and_belongs_to_many :serviceoverrides end The closest thing I've found explaining this online is on this blog but it doesn't really address what I'm trying to do (both manage the linkages to the other model, and edit attributes of that model. Any help is appreciated. Thanks in advance. Chris

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  • Using NHibernate to select entities based on activity of children entities

    - by mannish
    I'm having a case of the Mondays... I need to select blog posts based on recent activity in the post's comments collection (a Post has a List<Comment> property and likewise, a Comment has a Post property, establishing the relationship. I don't want to show the same post twice, and I only need a subset of the entities, not all of the posts. First thought was to grab all posts that have comments, then order those based on the most recent comment. For this to work, I'm pretty sure I'd have to limit the comments for each Post to the first/newest Comment. Last I'd simply take the top 5 (or whatever max results number I want to pass into the method). Second thought would be to grab all of the comments, ordered by CreatedOn, and filter so there's only one Comment per Post. Then return those top (whatever) posts. This seems like the same as the first option, just going through the back door. I've got an ugly, two query option I've got working with some LINQ on the side for filtering, but I know there's a more elegant way to do it in using the NHibernate API. Hoping to see some good ideas here.

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  • How to put foreign key constraints on a computed fields in sql server?

    - by Asaf R
    Table A has a computed field called Computed1. It's persisted and not null. Also, it always computes to an expression which is char(50). It's also unique and has a unique key constraint on it. Table B has a field RefersToComputed1, which should refer to a valid Computed1 value. Trying to create a foreign key constraint on B's RefersToComputed1 that references A' Computed1 leads to the following error: Error SQL01268: .Net SqlClient Data Provider: Msg 1753, Level 16, State 0, Line 1 Column 'B.RefersToComputed1' is not the same length or scale as referencing column 'A.Computed1' in foreign key 'FK_B_A'. Columns participating in a foreign key relationship must be defined with the same length and scale. Q: Why is this error created? Are there special measures needed for foreign keys for computed columns, and if so what are they? Summary: The specific problem rises from computed, char based, fields being varchar. Hence, Computed1 is varchar(50) and not char(50). It's best to have a cast surrounding a computed field's expression to force it to a specific type. Credit goes to Cade Roux for this tip.

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  • How can I filter these Django records?

    - by mipadi
    I have a set of Django models as shown in the following diagram (the names of the reverse relationships are shown in the yellow bubbles): In each relationship, a Person may have 0 or more of the items. Additionally, the slug field is (unfortunately) not unique; multiple Person records may have the same slug fields. Essentially these records are duplicates. I want to obtain a list of all records that meet the following criteria: All duplicate records (that is, having the same slug) with at least one Entry OR at least one Audio OR at least one Episode OR at least one Article. So far, I have the following query: Person.objects.values('slug').annotate(num_records=Count('slug')).filter(num_records__gt=1) This groups all records by slug, then adds a num_records attribute that says how many records have that slug, but the additional filtering is not performed (and I don't even know if this would work right anyway, since, given a set of duplicate records, one may have, e.g., and Entry and the other may have an Article). In a nutshell, I want to find all duplicate records and collapse them, along with their associated models, into one record. What's the best way to do this with Django?

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