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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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• 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 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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• 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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• 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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• '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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• 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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• 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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• What real life bad habits has programming given you? [closed]

  - by Jacob T. Nielsen

  Programming has given me a lot of bad habits and it continues to give me more everyday. But I have also gotten some bad habits from the mindset that I have put myself in. There simply are some things that are deeply rooted in my nature, though some of them I wish I could get rid of. A few: Looking for polymorphism, inheritance and patterns in all of God's creations. Explaining the size of something in pixels and colors in hex code. Using code related abstract terms in everyday conversations. How have you been damaged?

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• insert data into several tables

  - by csetzkorn

  Let us say I have a table (everything is very much simplified): create table OriginalData ( bla char(10) not null ) And I would like to insert its data (set based!) into two tables which model inheritance create table Statements ( Id int IDENTITY NOT NULL, ProposalDateTime DATETIME null ) create table Items ( StatementFk INT not null, ItemName NVARCHAR(255) null, primary key (StatementFk) ) Statements is the parent table and Items is the child table. I have no problem doing this with one row which involves the use of IDENT_CURRENT but I have no idea how to do this set based (i.e. enter several rows into both tables). Thanks. Best wishes, Christian

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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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• WPF DrawingVisual from my own class

  - by Robbskinizer

  Hi, Im trying to create my own class which contains a DrawingVisual, something like this public class MyObject { public DrawingVisual visual; public bool faceup; public bool flipped; } I have a drag and drop from a listview to a canvas, but when I try to get the object which back from the Canvas i only get the visual, not any of the other stuff in the class. How do i save "objects" and retreive it from a canvas? Im using my own MyCanvas which inheritance from Canvas, and using the AddVisualChild & AddLogicalChild etc. // Robbin

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• How do I map repeating columns in NHibernate without creating duplicate properties

  - by Ian Oakes

  Given a database that has numerous repeating columns used for auditing and versioning, what is the best way to model it using NHibernate, without having to repeat each of the columns in each of the classes in the domain model? Every table in the database repeats these same nine columns, the names and types are identical and I don't want to replicate it in the domain model. I have read the docs and I saw the section on inheritance mapping but I couldn't see how to make it work in this scenario. This seems like a common scenario because nearly every database I've work on has had the four common audit columns (CreatedBy, CreateDate, UpdatedBy, UpdateDate) in nearly every table. This database is no different except that it introduces another five columns which are common to every table.

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• VS 2010 Entity Repository Error

  - 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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• When is C++ covariance the best solution?

  - by Neil Butterworth

  This question was asked here a few hours ago and made me realise that I have never actually used covariant return types in my own code. For those not sure what covariance is, it's allowing the return type of (typically) virtual functions to differ provided the types are part of the same inheritance hierarchy. For example: struct A { virtual ~A(); virtual A * f(); ... }; struct B : public A { virtual B * f(); ... }; The different return types of the two f() functions are said to be covariant. Older versions of C++ required the return types to be the same, so B would have to look like: struct B : public A { virtual A * f(); ... }; So, my question: Does anyone have a real-world example where covariant return types of virtual functions are required, or produce a superior solution to simply returning a base pointer or reference?

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• Undefined behaviour with non-virtual destructors - is it a real-world issue?

  - by Roddy

  Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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• PHP5: restrict access to function to certain classes

  - by Tim

  Is there a way in PHP5 to only allow a certain class or set of classes to call a particular function? For example, let's say I have three classes ("Foo", "Bar", and "Baz"), all with similarly-named methods, and I want Bar to be able to call Foo::foo() but deny Baz the ability to make that call: class Foo { static function foo() { print "foo"; } } class Bar { static function bar() { Foo::foo(); print "bar"; } // Should work } class Baz { static function baz() { Foo::foo; print "baz"; } // Should fail } Foo::foo(); // Should also fail There's not necessarily inheritance between Foo, Bar, and Baz, so the use of protected or similar modifiers won't help; however, the methods aren't necessarily static (I made them so here for the simplicity of the example).

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• How can I use Object Oriented Javascript to interact with HTML Objects

  - by Steve

  I am very new to object orientated javascript, with experience writing gui's in python and java. I am trying to create html tables that I can place in locations throughout a webpage. Each html table would have two css layouts that control if it is selected or not. I can write all of the interaction if I only have one table. It gets confusing when I have multiple tables. I am wondering how to place these tables throughout a blank webpage and then access the tables individually. I think I am having trouble understanding how inheritance and hierarchy works in javascript/html. NOTE: I am not asking how to make a table. I am trying to dynamically create multiple tables and place them throughout a webpage. Then access their css independently and change it (move them to different locations or change the way the look, independently of the other tables).

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• Enterprise Library Validation Block - Should validation be placed on class or interface?

  - by Robert MacLean

  I am not sure where the best place to put validation (using the Enterprise Library Validation Block) is? Should it be on the class or on the interface? Things that may effect it Validation rules would not be changed in classes which inherit from the interface. Validation rules would not be changed in classes which inherit from the class. Inheritance will occur from the class in most cases - I suspect some fringe cases to inherit from the interface (but I would try and avoid it). The interface main use is for DI which will be done with the Unity block.

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• possible to show composition relationship in a diagram generated from PHP source code?

  - by ajsie

  i have tested several UML applications for whether they could show composition relationships in the UML diagrams generated form the PHP source code or not, and the result is they can't. i know that this is a typical problem for PHP cause we don't declare a data type when we code, so it's difficult for the UML applications to know if an instance variable is a reference to an object or not. i also tested nWire with the same result. will there never be applications that could show us a complete map over all object relationships more than just inheritance? i think it's a pity that you can't have a good view over all the relationships for an application. cause when i use an open source solution, i always want to know how the objects are related to each other. maybe we could make comments for the instance variable telling the software that this is an reference to an object? but that would mean that the mapping software is using this solution. i feel its a pity nWire/visual paradigm can't give us a complete map:(

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• contain new elements of an "instance" in javascript

  - by iamnotmad

  Hi, so I know there are tons of ways to simulate inheritance and other OO features. I have chosen one to use for my project and am wondering if I can create an instance and add stuff to it and keep it contained (within braces). Consider the following: function BaseClass(){ <this.stuff here> } function SubClass(){ this.superClass = BaseClass(); this.superClass(); <this.other stuff here> } myObj = new SubClass(); so myObj is an instance of SubClass. I can add things to myObj like: myObj.blah = "funtimes"; What I would like is to be able to add stuff to the "instance" and keep it organized in braces much like the constructor. psuedo code like: myObj = new SubClass() { var blah = "funtimes" <more instance specific stuff here> } Is something like this possible? Thanks!

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• Understanding reflection

  - by sdmiller

  I recently started work at a new company and a .net web application we have is built using reflection. I have only been out of school for a year and haven't worked with this concept. After studying the code... it looks like there is a single backend interface of type object that has about 20 classes that inherit from it. lots of generic gets and sets On the surface it looks like standard inheritance to me. I guess my question is, what makes this reflection? Is it because the interface is not strongly typed? Thanks

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• How/When/Where to Extend Gem Classes (via class_eval and Modules) in Rails 3?

  - by viatropos

  What is the recommended way to extend class behavior, via class_eval and modules (not by inheritance) if I want to extend a class buried in a Gem from a Rails 3 app? An example is this: I want to add the ability to create permalinks for tags and categories (through the ActsAsTaggableOn and ActsAsCategory gems). They have defined Tag and Category models. I want to basically do this: Category.class_eval do has_friendly_id :title end Tag.class_eval do has_friendly_id :title end Even if there are other ways of adding this functionality that might be specific to the gem, what is the recommended way to add behavior to classes in a Rails 3 application like this? I have a few other gems I've created that I want to do this to, such as a Configuration model and an Asset model. I would like to be able to add create an app/models/configuration.rb model class to my app, and it would act as if I just did class_eval. Anyways, how is this supposed to work? I can't find anything that covers this from any of the current Rails 3 blogs/docs/gists.

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• In Eclipse, how do I change the default modifiers in the class/type template?

  - by gustafc

  Eclipse's default template for new types (Window Preferences Code Style Code Templates New Java Files) looks like this: ${filecomment} ${package_declaration} ${typecomment} ${type_declaration} Creating a new class, it'll look something like this: package pkg; import blah.blah; public class FileName { // Class is accessible to everyone, and can be inherited } Now, I'm fervent in my belief that access should be as restricted as possible, and inheritance should be forbidden unless explicitly permitted, so I'd like to change the ${type_declaration} to declare all classes as final rather than public: package pkg; import blah.blah; final class FileName { // Class is only accessible in package, and can't be inherited } That seems easier said than done. The only thing I've found googling is a 2004 question on Eclipse's mailing list which was unanswered. So, the question in short: How can I change the default class/type modifiers in Eclipse? I'm using Eclipse Galileo (3.5) if that matters.

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• Propagate properties to parent control C#

  - by Martin Ch

  Is there any way how to propagate properties from child control into parent - so I can access property like - Parent.Property1 instead of Parent.Child.Property1 ? I cant use inheritance - my parent cant be extended child type - its inherited from different class. Also I dont wanna add code for each property from child to parent like: public object Property1 { get{ return Child.Property1; } set{ ChildProperty1 = value; } } Maybe using reflection - something like this? public PropertyInfo[] Properties { get{ return Child.GetType().GetProperties(); } set{ Child.GetType().GetProperties().SetValue() = value.GetValue()} } Thanks

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