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• Mixing table per subclass and per hierarchy in hibernate

  - by Xelluloid

  In my database there are two three tables. The first one, table ABSTRACT, holds three columns id, type, someText This table contains all abstract information for the abstract class abstract. Now the two tables CONCRETEONE and CONCRETETWO contain all information for the concrete classes concreteOne and concreteTwo. Now I know I could use the table per subclass strategy from hibernate to create a mapping with inheritance. But as I have a column that marks the type of the concrete implementation could it be possible to create some mixed behaviour like a table per subclass strategy with an discriminator?

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• How to isolate data per customer, Django powered website

  - by Sawwy

  I have recently started learning python and django and working on a project that includes building a website for collecting information from customers. I am currently trying to figure out best way to isolate the customer data (collected information is sensitive and should only be accessible by customer and the service provider). I found this post Postgresql - one database for everyone, or one-database per customer and my question is that can I automate the model inheritance with customer creation via admin? To be specific, when save() is called for adding customer via django admin, this should create the customer specific tables (create a new set of tables with 'company_name' -prefix). For more information of the environment, I have extended the basic user registration with custom UserProfile adding 'company' and 'role' fields for each user. Upon login, the 'company' of the user will be checked to filter out tables without the 'company_name' prefix. 'Role' will further filter the which company-specific tables and set rights (view, edit). will appreciate any suggestions if more elegant methods could be used to solve the data isolation problem than model inheritance.

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• Persisting non-entity class that extends an entity (jpa) - example?

  - by Michal Minicki

  The JPA tutorial states that one can have a non-entity that extends entity class: Entities may extend both entity and non-entity classes, and non-entity classes may extend entity classes. - http://java.sun.com/javaee/5/docs/tutorial/doc/bnbqa.html Is it possible to persist such structure? I want to do this: @Entity abstract class Test { ... } class FirstConcreteTest extends Test { ... } // Non-ntity class SecondConcreteTest extends Test { ... } // Non-entity Test test = new FirstConcreteTest(); em.persist(test); What I would like it to do is to persist all fields mapped on abstract Test to a common database table for all concrete classes (first and second), leaving all fields of first and second test class unpersisted (these can contain stuff like EJBs, jdbc pools, etc). And a bonus question. Is it possible to persist abstract property too? @Entity abstract class Test { @Column @Access(AccessType.PROPERTY) abstract public String getName(); } class SecondConcreteTest extends Test { public String getName() { return "Second Concrete Test"; } }

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• Inheritance security rules violated while overriding member - SecurityRuleSet.Level2

  - by Page Brooks

  I have a class that inherits from Exception. In .NET 4, I started receiving a runtime error: Inheritance security rules violated while overriding member: MyBusinessException.GetObjectData(System.Runtime.Serialization.SerializationInfo, System.Runtime.Serialization.StreamingContext)'. Security accessibility of the overriding method must match the security accessibility of the method being overriden. I think the issue is caused by the fact that I am overriding GetObjectData. I know one answer for resolving the issue is to set the SecurityRuleSet: [assembly: SecurityRules(SecurityRuleSet.Level1)] This is not an acceptable answer, I'd like to know how to fix the issue without having to relax the default security rules in .NET 4.

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• Entity Framework Model with inheritance and RIA Services

  - by TimothyP

  Hi, We have an entity framework model with has some inheritance in it. The following example is not the actuall model, but just to make my point... Let's say Base class: Person Child classes: Employee, Customer The database has been generated, the DomainService has been created and we can get to the data: lstCustomers.ItemsSource = context.Persons; EntityQuery<Person> query = context.GetPeopleQuery().Take(4); context.Load(query); But how can I modify the query to only return Customers ?

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• Inheritance of Custom Attributes on Abstract Properties

  - by Marty Trenouth

  I've got a custom attribute that I want to apply to my base abstract class so that I can skip elements that don't need to be viewed by the user when displaying the item in HTML. It seems that the properties overriding the base class are not inheriting the attributes. Does overriding base properties (abstract or virtual) blow away attributes placed on the original property? From Attribute class Defination [AttributeUsage(AttributeTargets.Property, Inherited = true, AllowMultiple = false)] public class NoHtmlOutput : Attribute { } From Abstract Class Defination [NoHtmlOutput] public abstract Guid UniqueID { get; set; } From Concrete Class Defination public override Guid UniqueID{ get{ return MasterId;} set{MasterId = value;}} From class checking for attribute Type t = o.GetType(); foreach (PropertyInfo pi in t.GetProperties()) { if (pi.GetCustomAttributes(typeof(NoHtmlOutput), true).Length == 1) continue; // processing logic goes here }

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• Using implicit conversion as a substitute for multiple inheritance in .NET

  - by Daniel Plaisted

  I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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• JSP template inheritance

  - by Ryan

  Coming from a background in Django, I often use "template inheritance", where multiple templates inherit from a common base. Is there an easy way to do this in JSP? If not, is there an alternative to JSP that does this (besides Django on Jython that is :) base template <html> <body> {% block content %} {% endblock %} </body> <html> basic content {% extends "base template" %} {% block content %} <h1>{{ content.title }} <-- Fills in a variable</h1> {{ content.body }} <-- Fills in another variable {% endblock %} Will render as follows (assuming that conten.title is "Insert Title Here", and content.body is "Insert Body Here") <html> <body> <h1>Insert title Here <-- Fills in a variable</h1> Insert Body Here <-- Fills in another variable </body> <html>

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• Table-per-type inheritance insert problem

  - by gzak

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

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• insert into several inheritance tables with OUTPUT - sql servr 2005

  - by csetzkorn

  Hi, I have a bunch of items – for simplicity reasons – a flat table with unique names seeded via bulk insert: create table #items ( ItemName NVARCHAR(255) ) The database has this structure: create table Statements ( Id INT IDENTITY NOT NULL, Version INT not null, FurtherDetails varchar(max) null, ProposalDateTime DATETIME null, UpdateDateTime DATETIME null, ProposerFk INT null, UpdaterFk INT null, primary key (Id) ) create table Item ( StatementFk INT not null, ItemName NVARCHAR(255) null, primary key (StatementFk) ) Here Item is a child of Statement (inheritance). I would like to insert items in #items using a set based approach (avoiding triggers and loops). Can this be achieved with OUTPUT in my scenario. A ‘loop based’ approach is just too slow where I use something like this: insert into Statements (Version, FurtherDetails, ProposalDateTime, UpdateDateTime, ProposerFk, UpdaterFk) VALUES (1, null, getdate(), getdate(), @user_id, @user_id) etc. This is a start for the OUTPUT based approach – but I am not sure whether this would work in my case as ItemName is only inserted into Item: insert into Statements ( Version, FurtherDetails, ProposalDateTime, UpdateDateTime, ProposerFk, UpdaterFk ) output inserted.Id ... ??? Thanks. Best wishes, Christian

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• C++ vtable resolving with virtual inheritance

  - by Tomas Cokis

  I was curious about C++ and virtual inheritance - in particular, the way that vtable conflicts are resolved between bass and child classes. I won't pretend to understand the specifics on how they work, but what I've gleamed so far is that their is a small delay caused by using virtual functions due to that resolution. My question then is if the base class is blank - ie, its virtual functions are defined as: virtual void doStuff() = 0; Does this mean that the resolution is not necessary, because there's only one set of functions to pick from? Forgive me if this is an stupid question - as I said, I don't understand how vtables work so I don't really know any better.

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• Rails table inheritance issue

  - by Tristan O'Neil

  I've setup some models in the table inheritance fashion and everything seems to be all fine and dandy. But, when I use a collection select field to select values from one of the models it saves it but it saves the ID of the data and not the actual value of the data. So when I try to display the value on the show view it just shows the corresponding ID and not the actual value. Here is my setup. I'm using formtastic as a side note. View <%= show_field "County", @company.county %> Form <%= f.input :county, :label => 'County', :as => :select, :collection => County.find(:all) %> Base Model class Tag < ActiveRecord::Base before_create :set_type before_update :set_type attr_accessible :type, :name, :category belongs_to :company def set_type self.type = self.category end end Inherited Model class County < Tag end

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• Inheritance in kohana

  - by Binaryrespawn

  Hi all, I have recently started to use Kohana and I know inheritance is in infancy stages at the moment. The work around is using a $_has_one annotation on the child class model. In may case i have "page" as the parent of "article". I have something like, protected $_has_one = array('mypage'=>array('model'=>'page', 'foreign_key'=>'id')); In my controller, I have an action which queries the database. In this query I am trying to access fields form the parent of "article" which is the "page". $n->articles=ORM::factory('article')->where('expires','=',0) ->where('articledate','<',date('y-m-d')) ->where('expirydate','>',date('y-m-d')) ->where('mypage->status','=','PUBLISHED') ->order_by('articledate','desc') ->find_all(); The status column resides in the page table and my query is generating an error to the effect of "cannot find status", clearly because it belongs to the parent. Any ideas ?

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• Inheritance vs specific types in Financial Modelling for cashflows

  - by BlueTrin

  Hello, I have to program some financial applications where I have to represent a schedule of flows. The flows can be of 3 types: - fee flow (just a lump payment at some date) - floating rate flow (the flow is dependant of an interest rate to be determined at a later date) - fixed rate flow (the flow is dependant of an interest rate determined when the deal is done) I need to keep the whole information and I need to represent a schedule of these flows. Originally I wanted to use inheritance and create three classes FeeFlow, FloatingFlow, FixedFlow all inheriting from ICashFlow and implement some method GetFlowType() returning an enum then I could dynamic_cast the object to the correct type. That would allow me to have only one vector to represent my schedule. What do you think of this design, should I rather use three vectors vector, vector and vector to avoid the dynamic casts ?

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• Template inheritance: X is not a template

  - by user2923917

  I am trying to build a inheritance-structure which looks like: Base - template Grandpa - template Father class Base {}; template <int x> class Grandpa: public Base {}; template <int x> class Father: public Grandpa<x> {}; However, the compiler complains when compiling Father, that Grandpa is not a template. I guess it is just some synthatic issue, however everything I've tried so far led to even more compiler complaints ;) Any idea whats wrong?

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• how to implement inheritance in hibernate ??

  - by user359057

  Hi guys i am working in a web application. I have a entities as BaseEntity --Which contains user login info like createdBy,createdTime,EditedBy,editedTime Employee -- which contains employee information like name,address,etc... RegularEmployee --which contains salary ,bonus tht kind of fields and ContactEmployee -- which contains HourlyRate,contactPeriod etc.... My inheritance structure is BaseEntity <--- Employee <---- RegularEmployee (i.e. Employee extends BaseEntity and RegularEmployee extends Employee ContractEmployee also extend Employee Class ). How to design database structure in this case considering all the tables have id and version fields (all tables should at least have these two fields).

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• [C++] Simple inheritance question

  - by xbonez

  I was going over some sample questions for an upcoming test, and this question is totally confusing me. Any help would be appreciated. Consider the following code: class GraduateStudent : public Student { ... }; If the word "public" is omitted, GraduateStudent uses private inheritance, which means which of the following? GraduateStudent objects may not use methods of Student. GraduateStudent does not have access to private objects of Student. No method of GraduateStudent may call a method of Student. Only const methods of GraduateStudent can call methods of Student.

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• [Principles] Concrete Type or Interface for method return type?

  - by SDReyes

  In general terms, whats the better election for a method's return type: a concrete type or an interface? In most cases, I tend to use concrete types as the return type for methods. because I believe that an concrete type is more flexible for further use and exposes more functionality. The dark side of this: Coupling. The angelic one: A concrete type contains per-se the interface you would going to return initially, and extra functionality. What's your thumb's rule? Is there any programming principle for this? BONUS: This is an example of what I mean http://stackoverflow.com/questions/491375/readonlycollection-or-ienumerable-for-exposing-member-collections

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• How to have operations with character/items in binary with concrete operations?

  - by Piperoman

  I have the next problem. A item can have a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can have some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have tried to set binary flags to states, and use AND to combine different states, checking before if it is possible or not to do it, or change to another status. Does there exist a concrete approach to solve this problem efficiently without having an interminable switch that checks every state with every new state? It is relatively easy to check 2 different states, but if there exists a third state it is not trivial to do.

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• How to have operations with character/items on binary with concrete operations on C++?

  - by Piperoman

  I have the next problem. A item can have a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can have some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have tried to set binary flags to states, and use AND to combine different states, checking before if it is possible or not to do it, or change to another status. Does there exist a concrete approach to solve this problem efficiently without having an interminable switch that checks every state with every new state? It is relatively easy to check 2 different states, but if there exists a third state it is not trivial to do.

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• How to had operation with character/items on binary with concrete operations on C++?

  - by Piperoman

  I have the next problem. A item can had a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can had some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have try to set binary flags to states, and use AND to set operation to combine different states, checking before if is possible or not to do it, or change to another status. Exist a concrete patron to solve this problem efficiently without had a interminable switch that check every states with everynew states? It is relative easy to check 2 different states, but if exist a third state it is not trivial to do.

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• Is this a pattern? Proxy/delegation of interface to existing concrete implementation

  - by Ian Newson

  I occasionally write code like this when I want to replace small parts of an existing implementation: public interface IFoo { void Bar(); } public class Foo : IFoo { public void Bar() { } } public class ProxyFoo : IFoo { private IFoo _Implementation; public ProxyFoo(IFoo implementation) { this._Implementation = implementation; } #region IFoo Members public void Bar() { this._Implementation.Bar(); } #endregion } This is a much smaller example than the real life cases in which I've used this pattern, but if implementing an existing interface or abstract class would require lots of code, most of which is already written, but I need to change a small part of the behaviour, then I will use this pattern. Is this a pattern or an anti pattern? If so, does it have a name and are there any well known pros and cons to this approach? Is there a better way to achieve the same result? Rewriting the interfaces and/or the concrete implementation is not normally an option as it will be provided by a third party library.

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• Can YAML have inheritance?

  - by Jason

  This question involves a lot of symfony but it should be easy enough for someone to follow who only knows YAML and not symfony. My symfony models come from a three-step process: First, I create the tables in MySQL. Second, I run a symfony command (symfony doctrine:build-schema) to convert my table structure into a YAML file. Third, I run another symfony command (symfony doctrine:build-model) to convert the YAML file into PHP code. Here's the problem: there are some tables in the database that I don't want to end up in my symfony code. For example, let's say I have two tables: one called my_table and another called wordpress. The YAML file I end up with might look like this: MyTable: connection: doctrine tableName: my_table Wordpress: connection: doctrine tableName: wordpress That's great except the wordpress table has nothing to do with my symfony models. The result is that every single time I make a change to my database and generate this YAML file, I have to manually remove wordpress. It's annoying! I'd like to be able to create a file called baseConfig.php or something that looks like this: $config = array( 'MyTable' => array( 'connection' => 'doctrine', 'tableName' => 'my_table', ), 'Wordpress' => array( 'connection' => 'doctrine', 'tableName' => 'wordpress', ), ); And then I could have a separate file called config.php or something where I could make modifications to the base config: unset($config['Wordpress']); So my question is: is there any way to convert YAML into executable PHP code (as opposed to load YAML INTO PHP code like what sfYaml::load() does) to achieve this sort of thing? Or is there maybe some other way to achieve YAML inheritance? Thanks, Jason

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• Inheritance using prototype / "new"

  - by mikkol

  Hi I'm new in Javascript OO and want to know more about about inheritance. Hope you can provide some advice! I see this great post: How to "properly" create a custom object in JavaScript? which talks about how a class is inherited as I see in other websites, ex.: function man(x) { this.x = x; this.y = 2; } man.prototype.name = "man"; man.prototype.two = function() { this.y = "two"; } function shawn() { man.apply(this, arguments); }; shawn.prototype = new man; The above post claims that in order not to call "man"'s constructor while inheriting, one can use a helper like this instead: function subclassOf(base) { _subclassOf.prototype= base.prototype; return new _subclassOf(); } function _subclassOf() {}; shawn.prototype = subclassOf(man); While I understand its intention, I don't see why we can't call shawn.prototype = man.prototype; I see it works exactly the same. Or is there something I'm missing? Thanks in advance!

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