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  • C#: Preferred pattern for functions requiring arguments that implement two interfaces

    - by JS Bangs
    The argument to my function f() must implement two different interfaces that are not related to each other by inheritance, IFoo and IBar. I know of two different ways of doing this. The first is to declare an empty interface that inherits from both: public interface IFooBar : IFoo, IBar { // nothing to see here } public int f(IFooBar arg) { // etc. } This, of course, requires that the classes declare themselves as implementing IFooBar rather than IFoo and IBar separately. The second way is to make f() generic with a constraint: public int f<T>(T arg) where T : IFoo, IBar { // etc. } Which of these do you prefer, and why? Are there any non-obvious advantages or disadvantages to each?

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  • Reverse Expression.Like criterion

    - by Joel Potter
    How should I go about writing a backwards like statement using NHibernate criteria? WHERE 'somestring' LIKE [Property] + '%' Sub Question: Can you access the abstract root alias in a SQLCriterion expression? This is somewhat achievable using the SQLCriterion expression Expression.Sql("? like {alias}.[Property] + '.%'", value, NHibernateUtil.String); However, in the case of class inheritance, {alias} is replaced with the incorrect alias for the column. Example (these classes are stored in separate tables): public abstract class Parent { public virtual string Property { get; set; } } public class Child : Parent { } The above query executed with Child as the root type will replace {alias} with the alias to the Child table rather than the Parent table. This results in an invalid column exception. I need to execute a like statement as above where the property exists on the parent table rather than on the root type table.

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  • In a Maven project, what are reasons for either a nested or a flat directory layout?

    - by Hanno Fietz
    As my Maven project grows, I'm trying to stay on top of the project structure. So far, I have a nested directory layout with 2-3 levels, where there's a POM on each level with module entries corresponding to the directories at that level. POM inheritance (parent property) does not necessarily follow this, and is not relevant for the purpose of this question. Now, while the nested structure seems pretty natural to Maven, and it's nice and clean as long as you are on one particular level, I'm starting to get confused by what I look at in my IDE (Eclipse and IntelliJ IDEA). I had a look at the Apache Felix sources, and they have a pretty complex project in what seems to be a flat directory structure, so I'm wondering if this would be a better way to go. What are some pros and cons for either approach that you have experienced in practice? Note that this question (which I found meanwhile) seems to be very similar. I'll leave it to the community to decide whether this should be closed as a duplicate.

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  • Teaching a mainframe COBOL programmer Java?

    - by Jared
    I’m trying to help someone learn Java who’s only programming experience is COBOL on the mainframe. I was wondering if anyone knew any good resources for object oriented concepts. I learned how to program with C++ so just understand the theory behind basic OOP. I’m more concerned about a way to get the basic concepts across, such as encapsulation and inheritance rather then Java syntax. I think it’d be better to teach the concepts of OOP then a language rather then trying to cram both a new language and paradigm in at the same time. Does anyone have any resources or ideas that could help this person learn OOP followed by Java?

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  • extra AuthorizationRule in web.config AuthorizationSection

    - by H07R0D
    I'm trying to modify the list of allowed users in web.config from a codebehind. <authorization> <allow users="alice, bob"/> <deny users="*"/> </authorization> I successfully retrieve the section I need config = WebConfigurationManager.OpenWebConfiguration("~"); authSection = (AuthorizationSection)config.GetSection("system.web/authorization"); When I iterate looking for the allow rule, I get two of them. foreach (AuthorizationRule rule in authSection.Rules) { if (rule.Action == AuthorizationRuleAction.Allow) { // manage the Users StringCollection } } The first item I get has 'alice' and 'bob' in the Users collection. The SECOND item I get has * Where is this second entry coming from? This is an Allow Rule, not a Deny rule. I could understand the * from a Deny rule. Is there some extra inheritance I'm not aware of?

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  • javascript inherance? with Private vars and methods too

    - by Totty
    Hy i need to inherent a class from another. Parent has private var "_data" and private method "_test" and public method "add" Now the child have a public method "add", that uses the private method from the parent "_test" and the private var "_data". How do i do this? var Parent = function(){ var _data = {}; var _test = function(){alert('test')}; this.add = function(){alert('add from parent')} } var Child = function(){ this.add = function(){// here uses the _data and _test from the Parent class alert('add from child') } } // something to inherent Child from Parent // instance Child and use the add method And i think im miss the prototype concept (http://stackoverflow.com/questions/892467/javascript-inheritance)

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  • C++ - what does the colon after a constructor mean?

    - by waitinforatrain
    I'd happily Google this but don't know what to call it to Google it. I have a piece of code here: class demo { private: unsigned char len, *dat; public: demo(unsigned char le = 5, unsigned char default) : len(le) { dat = new char[len]; for (int i = 0; i <= le; i++) dat[i] = default; } void ~demo(void) { delete [] *dat; } }; class newdemo : public demo { private: int *dat1; public: newdemo(void) : demo(0, 0) { *dat1 = 0; return 0; } }; (It's from a past exam paper and the question is to correct errors in the code so ignore errors!) My question is, what are the ": len(le) " and " : demo(0, 0)" called? Something to do with inheritance?

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  • Get class of caller's method (via inspect) in Python; or: super(Class,self).method() replacement wit

    - by Slava Vishnyakov
    Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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  • Constructor Type Coercion in C++

    - by Robert Mason
    Take the following class: class mytype { double num; public: mytype(int a) { num = sqrt(a); } void print() { cout << num; } } Say there is a method which takes a mytype: void foo(mytype a) { a.print(); } Is it legal c++ (or is there a way to implement this) to call foo(4), which would (in theory) output 2? From what I can glean you can overload type casts from a user defined class, but not to. Can constructor do this in a standards-compliant manner (assuming, of course, the constructor is not explicit). Hopefully there is a way to in the end have this legal: int a; cin >> a; foo(a); Note: this is quite obviously not the actual issue, but just an example for posting purposes. I can't just overload the function because of inheritance and other program-specific issues.

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  • OOP App Architecture: Which layer does a lazy loader sit in?

    - by JW
    I am planning the implemention an Inheritance Mapper pattern for an application component http://martinfowler.com/eaaCatalog/inheritanceMappers.html One feature it needs to have is for a domain object to reference a large list of aggreageted items (10,000 other domain objects) So I need some kind of lazy loading collection to be passed out of the aggregate root domain object to other domain objects. To keep my (php) model scripts organised i am storing them in two folders: MyComponent\ controllers\ models\ domain\ <- domain objects, DDD repository, DDD factory daccess\ <- PoEAA data mappers, SQL queries etc views\ But now I am racking my brains wondering where my lazy loading collection sits. Any suggestions / justifications for putting it in one place over another another? DDD = Domain Driven Design Patterns, Eric Evans - book PoEAA = Patterns of Application Architecture Patterns, Martin Fowler - book

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  • How to specify unique container styles for heterogenous hierarchies using SL3 and TreeView control

    - by rcecil
    Hello, Just look for strategies that have been successful in rendering hierarchies that represent inheritance structures using SL3/4 TreeViews. I need to render certain nodes differently than others, depending upon what kind of container they are (a choice between things, or simply a list of related things, etc.) So far, I've been very successful with the DataTemplate route: I've been able to use a technique described in Ted Glaza's post "Easy DataTemplateSelectors in Silverlight" (you may have retrieve a Google cache of this page). SO what I'm trying to discover is something on the order of a StyleSelector, not a DataTemplateSelector. I'm considering leveraging my current implementations of Glaza's pattern of selector objects to somehow detect the node type and set the ItemContainerStyle there, but it doesn't seem clear right now. Thanks for your thoughts.

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  • VS 2010 Entity Repository Error Class member EntityBase.id is unmapped.

    - by Steve
    In my project I have it set up so that all the tables in the DB has the property "id" and then I have the entity objects inherit from the EntityBase class using a repository pattern. I then set the inheritance modifier for "id" property in the dbml file o/r designer to "overrides" Public MustInherit Class EntityBase MustOverride Property id() As Integer End Class Public MustInherit Class RepositoryBase(Of T As EntityBase) Protected _Db As New DataClasses1DataContext Public Function GetById(ByVal Id As Integer) As T Return (From a In _Db.GetTable(Of T)() Where a.id = Id).SingleOrDefault End Function End Class Partial Public Class Entity1 Inherits EntityBase End Class Public Class TestRepository Inherits RepositoryBase(Of Entity1) End Class the line Return (From a In _Db.GetTable(Of T)() Where a.id = Id).SingleOrDefault however produces the error "Class member EntityBase.id is unmapped" when i use VS 2010 using the 4.0 framework but I never received that error with the old one. Any help would be greatly appreciated. Thanks in advance.

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  • casting between sibling classes, AS3

    - by felix-gasca
    I have two classes, derivedClassA and derivedClassB which both extend parentClass I'm declaring var o:parentClass and then, depending on what's going on, I want to cast o as either being of type derivedClassA or derivedClassB. Essentially, this: var o:parentClass ... if(shouldUseA) o = new derivedClassA(); else o = new derivedClassB(); o.doSomething(); But it's not working, I'm getting all sorts of errors. Isn't this how class inheritance works? I feel like I'm missing something really fundamental, but I can't figure out what. Am I supposed to be using interfaces instead? Is there another way of doing what I want?

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  • Can I serialize a BitArray to XML?

    - by SimonNet
    Hello I have a business class which I need to serialize to xml. It has a BitArray property. I have decorated it with [XmlAttribute] but the serialization is failing with To be XML serializable, types which inherit from ICollection must have an implementation of Add(System.Boolean) at all levels of their inheritance hierarchy. System.Collections.BitArray does not implement Add(System.Boolean). I am not sure whether its possible to serialize to xml? If not what would be an efficient means of serializing the BitArray Thanks for looking

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  • Has anybody managed to teach themself strong OOP skills through mainly developing with JavaScript?

    - by yaya3
    I am trying to do this, I'm a full time front-end dev and am aware that I am struglling to achieve this. When I am referring to OOP skills I am referring to understanding and being familiar with concepts like inheritance, polymorphism, encapsulation, abstaction. I am aware that it may be more likely to achieve what I'm after by focusing on another language in my spare time. This is the plan, but I'd be really intrigued to hear if anybody has managed to achieve this purely through JavaScript and how you did it. It'd be even better to hear from strong OOP developers from who use different programming languages to know if they have worked with developers who have managed to achieve this.

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  • Metric to measure object-orientedness

    - by Jono
    Is there a metric that can assist in determining the object-orientedness of a system or application? I've seen some pretty neat metrics in the .NET Reflector Add-ins codeplex project, but nothing like this yet. If such a metric doesn't exist, would it even be possible or useful? There are the 3 supposed tenets of object-oriented programming: encapsulation, inheritance, and polymorphism; a tool that ranked programs against these might be able to show areas of a C# (or similar) code base where the whole object-oriented ideal was discarded, and perhaps how many bugs are associated with that area versus the rest of the project.

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  • What's the best way to share one Entity Framework 4 data model among multiple applications (meant to

    - by Ivan
    A project (a "solution" to say in VS terms) of mine consists of an ASP.Net 4 Dynamic Data Entities web application, some WinForms applications, some WPF applications, some services. All they are intended to work with one SQL Server database, generated from an Entity Framework 4 model as table-per-type, with lots of inheritance and multiple self-referencing relations. Where do I best put my model? In a separate class library, a copy in every project, in one project, etc. What naming should I best use? Is it good idea to name it MySolution.MyClassLibrary.MySolutionEntities, or just MySolutionEntities or just MySolution? Can you share any useful experience on this subject?

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  • How do I dynamically assign the Model for a .find in Ruby on Rails?

    - by Angela
    I am trying to create a Single Table Inheritance. However, the Controller must be able to know which class to find or create. These are based on another class. For example, ContactEvent with type = Letter needs to grab attributes from a corresponding Model called Letter. Here's what I've tried to do and hit a snag, labelled below. I need to be able to dynamically call assign a value of EventClass so that it can be Letter.find(:conditions =) or Calls.find(:conditions =) depending on which type the controller is acting on. def new @contact_event = ContactEvent.new @contact_event.type = params[:event_type] # can be letter, call, postcard, email @contact_event.event_id = params[:event_id] # that ID to the corresponding Model @contact_event.contact_id = params[:contact] @EventClass = case when @contact_event.type == 'letter' then 'Letter' when @contact_event.type == 'call' then 'Call' when @contact_event.type == 'email' then 'Email' SNAG BELOW: @event = @EventClass.find(@contact_letter.letter_id) #how do I make @EventClass actually the Class?SNAG # substitution of variables into the body of the contact_event @event.body.gsub!("{FirstName}", @contact.first_name) @event.body.gsub!("{Company}", @contact.company_name) @evebt.body.gsub!("{Colleagues}", @colleagues.to_sentence) @contact_event.body = @event.body @contact_event.status = "sent" end

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  • WPF: Hidden parent and visible child

    - by oakskc
    As of last night, I decided to start learning about WPF and have been reading through a number of online tutorials and books. This is a huge shift. One feature that has fascinated me is the implicit property value inheritance. I know in the WinForms world, if a control is not visible then neither are any of the child controls. Same seems to be true in the WPF world, as expected. I wondered if explicitly setting the child control's Visibility property would allow for an invisible parent and visible child and it did not. Is this something that would be possible in WPF? Can you have a container control that is hidden with visible children? This is more an exercise of curiosity than anything. I'm still trying to wrap my head around a lot of what I've been reading.

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  • how to force ejb3 to reload value from data base and not use those of the context

    - by Kohan95
    Hello here I have a big problem that I hope to find help here I have two entities @Entity @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorColumn(name="Role", discriminatorType=DiscriminatorType.STRING) public class Utilisateur implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="id") private Long id; @Column(name="nom",nullable=false) private String nom; @Column(name="Role",nullable=false, insertable=false) private String Role ; //... } @Entity @Table(name="ResCom") @DiscriminatorValue("ResCom") public class ResCom extends Utilisateur { /... } the first thing I do ResCom rsCom= new ResCom(nom,prenom, email,civilite, SysQl.crypePasse(pass)); gr.create(rsCom); I check my database I see that property is ResCom insert but when I check the value of role I get null Utilisateur tets= gr.findByEmail(email); message=tets.getEmail()+" and Role :"+tets.getRole()+""; but in my bass it ResCom !!!!! the problem disappears when I deploy the project again I hope you have a solution And thank you in advance sorry for my English

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  • Suggested C++ books?

    - by Josh Bradley
    Ok, I've had one semester of C++ and will be taking a second semester in it after I have taken a Data Structure class this fall. In the first class, we dealt mainly with C++ syntax and the textbook we used was ok, but now I'm wanting to go ahead and purchase a great C++ book that encompasses a lot of the programming concepts used today. I'm learning Objective-C on my own and was able to get through the whole object-oriented stuff pretty easily, along with other things like pointers, inheritance, delegation, etc. It doesn't have to exactly have EVERYTHING in it, but I do want to buy the book with the most information in it. Money is no problem. So my question is what book did you use or still use for C++? Is it a book that you can reference back to if you ever forget how to do something small, or would you have to go online and find the answer.

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  • 'is instanceof' Interface bad design

    - by peterRit
    Say I have a class A class A { Z source; } Now, the context tells me that 'Z' can be an instance of different classes (say, B and C) which doesn't share any common class in their inheritance tree. I guess the naive approach is to make 'Z' an Interface class, and make classes B and C implement it. But something still doesn't convince me because every time an instance of class A is used, I need to know the type of 'source'. So all finishes in multiple 'ifs' making 'is instanceof' which doesn't sound quite nice. Maybe in the future some other class implements Z, and having hardcoded 'ifs' of this type definitely could break something. The escence of the problem is that I cannot resolve the issue by adding functions to Z, because the work done in each instance type of Z is different. I hope someone can give me and advice, maybe about some useful design pattern. Thanks

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  • Questions about my program and Polymorphism

    - by Strobe_
    Ok, so basically I'm creating a program which allows the user to select a shape (triangle, square, circle) and then it takes in a int and calculates the boundary length and area. I have no problem doing this and have a program that's working perfectly. (https://gist.github.com/anonymous/c63a03c129560a7b7434 4 classes) But now I have to implement this with polymorphism concepts and I'm honestly struggling as to how to do it. I have a basic idea of what I want to do when it comes to inheritance Main | Shapes / | \ triangle circle square But I don't understand how I'm supposed to override when all the methods within the triangle/square/circle classes are unique, there are no "abstract" methods as such that I could inherit from the "Shapes" class. If somebody could make look quickly at the code I linked and suggest a way to do this it would be much appreciated. Sorry if I was bad at explaining this. Thanks.

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  • rails: has_many :through + polymorphism validation?

    - by ramonrails
    I am trying to achieve this. Any hints? A project has many users through join model A user has many projects through join model Admin class inherits User class. It also has some Admin specific stuff. Admin like inheritance for Supervisor and Operator Project has one Admin, One supervisor and many operators. Now I want to 1. submit data for project, admin, supervisor and operator in a single project form 2. validate all and show errors on the project form. Project has_many :users, :through = :projects_users User has_many :projects, :through = :projects_users ProjectsUser = :id integer, :user_id :integer, :project_id :integer, :user_type :string ProjectUser belongs_to :project, belongs_to :user, :polymorphic = true Admin < User Supervisor < User Operator < User Is the approach correct? Any and all suggestions are welcome.

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  • Get class of caller's method (via inspect) in Python

    - by Slava Vishnyakov
    Is it possible to get reference to class B in this example? class A(object): pass class B(A): def test(self): test2() class C(B): pass import inspect def test2(): frame = inspect.currentframe().f_back cls = frame.[?something here?] # cls here should == B (class) c = C() c.test() Basically, C is child of B, B is child of A. Then we create c of type C. Then the call to c.test() actually calls B.test() (via inheritance), which calls to test2(). test2() can get the parent frame frame; code reference to method via frame.f_code; self via frame.f_locals['self']; but type(frame.f_locals['self']) is C (of course), but not B, where method is defined. Any way to get B?

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