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  • Core Data not-reverse relationship subquery

    - by user561485
    Hi, I have the following entities in CoreData: Village - villageID Bookmark - (relation) village There are multiple villages with each an unique villageID. I have a entity Bookmark which only has a relation to a Village entity; it isn't possible to make a reverse relation. Now I would like to get the village entities where there exists a Bookmark relation. I've red something about subqueries, but I can't get it right for this situation. It must be something like: Village.villageID IN (Bookmark.village.villageID) It isn't possible to get first all the Bookmarks and then loop to get all the Villages, because of the design of the framework. Can this be done in CoreData (I presume the answer is "Yes, of course!") and how?

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  • Rails: bi-directional has_many :through relationship

    - by Chris
    I have three models in a Rails application: Game represents an instance of a game being played. Player represents an instance of a participant in a game. User represents a registered person who can participate in games. Each Game can have many Players, and each User can have many Players (a single person can participate in multiple games at once); but each Player is in precisely one Game, and represents precisely one User. Hence, my relationships are as follows at present. class Game has_many :players end class User has_many :players end class Player belongs_to :game belongs_to :user end ... where naturally the players table has game_id and user_id columns, but games and users have no foreign keys. I would also like to represent the fact that each Game has many Users playing in it; and each User has many Games in which they are playing. How do I do this? Is it enough to add class Game has_many :users, :through => :players end class User has_many :games, :through => :players end

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  • Entity framework Update fails when object is linked to a missing child

    - by McKay
    I’m having trouble updating an objects child when the object has a reference to a nonexising child record. eg. Tables Car and CarColor have a relationship. Car.CarColorId CarColor.CarColorId If I load the car with its color record like so this var result = from x in database.Car.Include("CarColor") where x.CarId = 5 select x; I'll get back the Car object and it’s Color object. Now suppose that some time ago a CarColor had been deleted but the Car record in question still contains the CarColorId value. So when I run the query the Color object is null because the CarColor record didn’t exist. My problem here is that when I attach another Color object that does exist I get a Store update, insert error when saving. Car.Color = newColor Database.SaveChanges(); It’s like the context is trying to delete the nonexisting color. How can I get around this?

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  • Entity Framework - Store parent reference on child relationship (one -> many)

    - by contactmatt
    I have a setup like this: [Table("tablename...")] public class Branch { public Branch() { Users = new List<User>(); } [Key] public int Id { get; set; } public string Name { get; set; } public List<User> Users { get; set; } } [Table("tablename...")] public class User { [Key] public int Id {get; set; } public string Username { get; set; } public string Password { get; set; } [ForeignKey("ParentBranch")] public int? ParentBranchId { get; set; } // Is this possible? public Branch ParentBranch { get; set; } // ??? } Is it possible for the User to know what parent branch it belongs to? The code above is not working. Entity Framework version 5.0 .NET 4.0 c#

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  • Audit many-to-many relationship in NHibernate

    - by Kendrick
    I have implemented listeners to audit changes to tables in my application using IPreUpdateEventListener and IPreInsertEventListener and everything works except for my many-to-many relationships that don't have additional data in the joining table (i.e. I don't have a POCO for the joining table). Each auditable object implements an IAuditable interface, so the event listener checks to see if a POCO is of type IAuditable, and if it is it records any changes to the object. Look up tables implement an IAuditableProperty inteface, so if a property of the IAuditable POCO is pointing to a lookup table, the changes are recorded in the log for the main POCO. So, the question is, how should I determine I'm working with a many-to-many collection and record the changes in my audit table? //first two checks for LastUpdated and LastUpdatedBy ommitted for brevity else if (newState[i] is IAuditable) { //Do nothing, these will record themselves separately } else if (!(newState[i] is IAuditableProperty) && (newState[i] is IList<object> || newState[i] is ISet)) { //Do nothing, this is a collection and individual items will update themselves if they are auditable //I believe this is where my many-to-many values are being lost } else if (!isUpdateEvent || !Equals(oldState[i], newState[i]))//Record only modified fields when updating { changes.Append(preDatabaseEvent.Persister.PropertyNames[i]) .Append(": "); if (newState[i] is IAuditableProperty) { //Record changes to values in lookup tables if (isUpdateEvent) { changes.Append(((IAuditableProperty)oldState[i]).AuditPropertyValue) .Append(" => "); } changes.Append(((IAuditableProperty)newState[i]).AuditPropertyValue); } else { //Record changes for primitive values if(isUpdateEvent) { changes.Append(oldState[i]) .Append(" => "); } changes.Append(newState[i]); } changes.AppendLine(); }

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  • How to insert rows in a many-to-many relationship

    - by GSound
    Hello, I am having an issue trying to save into an intermediate table. I am new on Rails and I have spent a couple of hours on this but can't make it work, maybe I am doing wrong the whole thing. Any help will be appreciated. =) The app is a simple book store, where a logged-in user picks books and then create an order. This error is displayed: NameError in OrderController#create uninitialized constant Order::Orderlist These are my models: class Book < ActiveRecord::Base has_many :orderlists has_many :orders, :through => :orderlists end class Order < ActiveRecord::Base belongs_to :user has_many :orderlists has_many :books, :through => :orderlists end class OrderList < ActiveRecord::Base belongs_to :book belongs_to :order end This is my Order controller: class OrderController < ApplicationController def add if session[:user] book = Book.find(:first, :conditions => ["id = #{params[:id]}"]) if book session[:list].push(book) end redirect_to :controller => "book" else redirect_to :controller => "user" end end def create if session[:user] @order = Order.new if @order.save session[:list].each do |b| @order.orderlists.create(:book => b) # <-- here is my prob I cant make it work end end end redirect_to :controller => "book" end end Thnx in advance! Manuel

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  • Hibernate many-to-many relationship

    - by Capitan
    I have two mapped types, related many-to-many. @Entity @Table(name = "students") public class Student{ ... @ManyToMany(fetch = FetchType.EAGER) @JoinTable( name = "students2courses", joinColumns = { @JoinColumn( name = "student_id", referencedColumnName = "_id") }, inverseJoinColumns = { @JoinColumn( name = "course_id", referencedColumnName = "_id") }) public Set<Course> getCourses() { return courses; } public void setCourses(Set<Course> courses) { this.courses = courses; } ... } __ @Entity @Table(name = "courses") public class Course{ ... @ManyToMany(fetch = FetchType.EAGER, mappedBy = "courses") public Set<Student> getStudents() { return students; } public void setStudents(Set<Student> students) { this.students = students; } ... } But if I update/delete Course entity, records are not created/deleted in table students2courses. (with Student entity updating/deleting goes as expected) I wrote abstract class HibObject public abstract class HibObject { public String getRemoveMTMQuery() { return null; } } which is inherited by Student and Course. In DAO I added this code (for delete() method): String query = obj.getRemoveMTMQuery(); if (query != null) { session.createSQLQuery(query).executeUpdate(); } and I ovrerided method getRemoveMTMQuery() for Course @Override @Transient public String getRemoveMTMQuery() { return "delete from students2courses where course_id = " + id + ";"; } Now it works but I think it's a bad code. Is there a best way to solve this problem?

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  • Core Data to-many relationship in code

    - by Jan Bezemer
    I have three entities: Session, User and Test. A session has 0-many users and a user can perform 0-6 tests. (I say 0 but in the real application always at least 1 is required, at least 1 user for a session and at least 1 test for a user. But I say 0 to express an empty start.) All entities have their own specific data attributes too. A user has a name, A session has a name, a test has six values to be filled in by the user, and so on. But my issue is with the relationships. How do I set multiple users and have them added to one session (same goes for multiple tests for one user). How do I show the content in a right way? How do I show a session that has multiple users and these users having completed multiple tests? Here's my code so far with regard to issue 1: Session *session = [NSEntityDescription insertNewObjectForEntityForName:@"Session" inManagedObjectContext:context]; session.name = @"Session 1"; User *users = [NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:context]; users.age = [NSNumber numberWithInt:28]; users.session = session; //sessie.users = users; [sessie addUserObject:users]; With regard to issue 2: I can log the session, but I can't get the user(s) logged from a session. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Session" inManagedObjectContext:context]; [fetchRequest setEntity:entity]; NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error]; for (Session *info in fetchedObjects) { NSLog(@"Name: %@", info.name); NSLog(@"Having problems with this: %@",info.user); //User *details = info.user; //NSLog(@"User: %@", details.age); }

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  • MySQL: List rows who have one but not another many-to-many relationship

    - by Svish
    Not quite sure how to ask or define this, but can't figure it out. I have three tables like this: persons person_id, first_name, last_name hobbies hobby_id, name persons_hobbies person_id, hobby_id I need to make two lists. Persons that have both hobby A and B, and persons that have hobby A but not B. How can I write these two queries? Can't figure out how to do this with joining and all...

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  • 1:M relationship in Hibernate and cascading operations

    - by EugeneP
    Table SUBCOURSE references COURSE COURSE(id, name) SUBCOURSE(id, course_id, name) So, 1:M. Hibernate generates for Course: @OneToMany(fetch = FetchType.LAZY, mappedBy = "course", cascade = CascadeType.ALL) public Set getSubCourses() { return this.subCourses; } for Subcourse it generates @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "course_id", nullable = false) public Course getCourse() { return this.course; } Now the problem is that cascading does not work as expected. I want to create a collection of SubCourse objects (Set), fill it and then bind it to setSubCourses() of Course object. Though, having ManyToOne thing in a Subcourses table, I need to manually setCourse() before adding to collection on each object. If I do not do so, an exception is raised. What can you recommend me?

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  • many-to-many relationship in CI (not using ORM)

    - by Ross
    I'm implementing a categories system in my CI app and trying to work out the best way of working with many to many relationships. I'm not using an ORM at this stage, but could use say Doctrine if necessary. Each entry may have multiple categories. I have three tables (simplified) Entries: entryID, entryName Categories: categoryID, categoryname Entry_Category: entryID, categoryID my CI code returns a record set like this: entryID, entryName, categoryID, categoryName but, as expected with Many-to-Many relationships, each "entry" is repeated for each "category". What would the best way to "group" the categories so that when I output the results, I am left with something like: Entry Name Appears in Category: Foo, Bar rather than: Entry Name Appears in Category: Foo Entry Name Appears in Category: Bar I believe the option is to track if the post ID matches a previous entry, and if so, store the respective category, and output it as one, rather than several, but am unsure of how to do this in CI. thanks for any pointers (I appreciate this is may be a vague/complex question without a better knowledge of the system).

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  • Rails - column not found for defined 'has_many' relationship

    - by Guanlun
    I define a Post class which can link or be linked to multiple posts. To do this I added a PostLink class which specifies post_to and post_from. I generated the PostLink class by rails g model post_link from_post:integer to_post:integer and of course rake db:migrate, and added belongs_to :from_post, :class_name => 'Post' belongs_to :to_post, :class_name => 'Post' to the class. And I also have has_many :post_links in my Post class. I ran rails console and Post.new.post_links and got nil printed out, which is expected. However after I save a Post using p = Post.new p.save and then run p.post_links, it prints out the following error message: SQLite3::SQLException: no such column: post_links.post_id: SELECT "post_links".* FROM "post_links" WHERE "post_links"."post_id" = 1 So anybody know why after saving it to the database post_link can not be accessed?

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  • C# Access the Properties of a Generic Object

    - by Jimbo
    I have a method that counts the number of Contacts each Supplier, Customer and Manufacturer has (this is a scenario to try make explaining easier!) The models are all created by Linq to SQL classes. Each Supplier, Customer and Manufacturer may have one or more Contacts public int CountContacts<TModel>(TModel entity) where TModel : class { return entity.Contacts.Count(); } The above of course doesnt work, because the 'entity' is generic and doesnt know whether it has the property 'Contacts'. Can someone help with how to achieve this?

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  • Generic method to create deep copy of all elements in a collection

    - by bwarner
    I have various ObservableCollections of different object types. I'd like to write a single method that will take a collection of any of these object types and return a new collection where each element is a deep copy of elements in the given collection. Here is an example for a specifc class private static ObservableCollection<PropertyValueRow> DeepCopy(ObservableCollection<PropertyValueRow> list) { ObservableCollection<PropertyValueRow> newList = new ObservableCollection<PropertyValueRow>(); foreach (PropertyValueRow rec in list) { newList.Add((PropertyValueRow)rec.Clone()); } return newList; } How can I make this method generic for any class which implements ICloneable?

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  • Generic Data Structure Description Language

    - by Jon Purdy
    I am wondering whether there exists any declarative language for arbitrarily describing the format and semantics of a data structure, that can be compiled to a specific implementation of that structure in any of a set of target languages. That is, something like a generic data definition language but geared toward describing arbitrary data structures such as vectors, lists, trees, etc., and the semantics of operations on those structures. I ask because I had an idea for a feasible implementation of this concept, and I'm just wondering whether it's worth it, and, consequently, whether it's been done before. Another, slightly more abstract question: is there any real difference between the normative specification of a data structure (what it does) and its implementation (how it does it)?

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  • Calling generic method in spring.net application context

    - by Bert Vandamme
    Hi, I'm trying to invoke this method in spring.net, but i'm having trouble getting the configuration right. Method: public void AddRepository(IRepository repository) where TEntity : IEntity { Repositories.Add(repository.GetType().Name, repository); } Config: <object type="Spring.Objects.Factory.Config.MethodInvokingFactoryObject, Spring.Core"> <property name="TargetObject"> <ref local="RepositoryFactory" /> </property> <property name="TargetMethod" value="AddRepository"/> <property name="Arguments"> <list> <ref object="BinaryAssetFileRepository"/> </list> </property> </object>" Is it possible to address generic methods in this way? Thx, Bert

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  • Is generic Money<T_amount> a good idea?

    - by jdk
    I have a Money Type that allows math operations and is sensitive to exchange rates so it will reduce one currency to another if rate is available to calculate in a given currency, rounds by various methods. It has other features that are sensitive to money, but I need to ask if the basic data type used should be made generic in nature. I've realized that the basic data type to hold an amount may differ for financial situations, for example: retail money might be expressed as all cents using int or long where fractions of cents do not matter, decimal is commonly used for its fixed behaviour, sometimes double seems to be used for big finance and large values sometimes a special BigInteger or 3rd-party type is used. I want to know if it would be considered good form to turn Money into Money<T_amount> so it can be used in any one of the above chosen scenarios?

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  • Generic type parameters using out

    - by Mikael
    Im trying to make a universal parser using generic type parameters, but i can't grasp the concept 100% private bool TryParse<T>(XElement element, string attributeName, out T value) where T : struct { if (element.Attribute(attributeName) != null && !string.IsNullOrEmpty(element.Attribute(attributeName).Value)) { string valueString = element.Attribute(attributeName).Value; if (typeof(T) == typeof(int)) { int valueInt; if (int.TryParse(valueString, out valueInt)) { value = valueInt; return true; } } else if (typeof(T) == typeof(bool)) { bool valueBool; if (bool.TryParse(valueString, out valueBool)) { value = valueBool; return true; } } else { value = valueString; return true; } } return false; } As you might guess, the code doesn't compile, since i can't convert int|bool|string to T (eg. value = valueInt). Thankful for feedback, it might not even be possible to way i'm doing it. Using .NET 3.5

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  • Issue converting Sitecore Item[] using ToList<T>

    - by philba888
    Working with Sitecore and Linq extensions. I am trying to convert to from an item array to the list using the following piece of code: Item variationsFolder = masterDB.SelectSingleItem(VariationsFolderID.ToString()); List<Item> variationList = variationsFolder.GetChildren().ToList<Item>(); However I keep getting this error whenever I try to build: 'Sitecore.Collections.ChildList' does not contain a definition for 'ToList' and the best extension method overload 'System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>)' has some invalid arguments I have the following usings: using System.Linq; using System.Xml.Linq; Am referencing: System.Core I've just copied this code from another location, so it should work fine, can only think that there is something simple (like a reference or something that I am missing).

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  • calling Overloaded method from a generic method.

    - by asela38
    How to create a generic method which can call overloaded methods? I tried but it gives a compilation error. Test.java:19: incompatible types found : java.lang.Object required: T T newt = getCloneOf(t); ^ import java.util.*; public class Test { private Object getCloneOf(Object s) { return new Object(); } private String getCloneOf(String s) { return new String(s); } private <T> Set<T> getCloneOf(Set<T> set){ Set<T> newSet = null; if( null != set) { newSet = new HashSet<T>(); for (T t : set) { T newt = getCloneOf(t); newSet.add(newt); } } } }

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  • Using Generics to typecast object type to generic type

    - by Shantanu Gupta
    I am very new to generics and trying to implement it. How can i use it here. private T returnValueFromGrid(int RowNo, int ColNo) { return Converter<dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value,T>; } I am trying to convert below value to generic type and then return it. dgvCurrencyMaster.Rows[RowNo].Cells[ColNo].Value Here i need to know two things. How to do the above problem and how to use this in my code. Please provide some eg.

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  • Is generic Money<TAmount> a good implementation idea?

    - by jdk
    I have a Money Type that allows math operations and is sensitive to exchange rates so it will reduce one currency to another if rate is available to calculate in a given currency, rounds by various methods. It has other features that are sensitive to money, but I need to ask if the basic data type used should be made generic in nature. I've realized that the basic data type to hold an amount may differ for financial situations, for example: retail money might be expressed as all cents using int or long where fractions of cents do not matter, decimal is commonly used for its fixed behaviour, sometimes double seems to be used for big finance and large values sometimes a special BigInteger or 3rd-party type is used. I want to know if it would be considered good form to turn Money into Money<T_amount> so it can be used in any one of the above chosen scenarios?

    Read the article

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