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• Inheriting from class that inherits from DynamicObject

  - by SeveQ

  Hello there, I'm experimenting with C# 4.0's dynamic object model. I've created an abstract class named "Block" that inherits from DynamicObject. It overrides TryGetMember and TrySetMember. Furthermore I've created a usable class named "Brush" that inherits from "Block". I want it to be usable dynamically. But when I create a dynamic object from it and try to access a runtime bound member, it pelts me with an exception telling me that the member doesn't exist. The overridden TryGetMember or TrySetMember methods of the abstract parent class aren't getting called. Is this behaviour to be expected? Thank you!

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• Mapping self-table one-to-many using non-PK clolumns

  - by Harel Moshe

  Hey, i have a legacy DB to which a Person object is mapped, having a collection of family-members, like this: class Person { ... string Id; /* 9-digits string */ IList<Person> Family; ... } The PERSON table seems like: Id: CHAR(9), PK FamilyId: INT, NOT NULL and several other non-relevant columns. I'm trying to map the Family collection to the PERSON table using the FamilyId column, which is not the PK as mentioned above. So, i actually have a one-to-many which is self-table-referential. I'm getting an error saying 'Cast is not valid' when my mapping looks like this: ... <set name="Family" table="Person" lazy="false"> <key column="FamilyId" /> <one-to-many class="Person" /> </set> ... because obviously, the join NHibernate is trying to make is between the PK column, Id, and the 'secondary' column, FamilyId, instead of joining the FamilyId column to itself. Any ideas please?

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• Calling function using 'new' is less expensive than without it?

  - by Matthew Taylor

  Given this very familiar model of prototypal construction: function Rectangle(w,h) { this.width = w; this.height = h; } Rectangle.prototype.area = function() { return this.width * this.height; }; Can anyone explain why calling "new Rectangle(2,3)" is consistently 10x FASTER than calling "Rectangle(2,3)" without the 'new' keyword? I would have assumed that because new adds more complexity to the execution of a function by getting prototypes involved, it would be slower. Example: var myTime; function startTrack() { myTime = new Date(); } function stopTrack(str) { var diff = new Date().getTime() - myTime.getTime(); println(str + ' time in ms: ' + diff); } function trackFunction(desc, func, times) { var i; if (!times) times = 1; startTrack(); for (i=0; i<times; i++) { func(); } stopTrack('(' + times + ' times) ' + desc); } var TIMES = 1000000; trackFunction('new rect classic', function() { new Rectangle(2,3); }, TIMES); trackFunction('rect classic (without new)', function() { Rectangle(2,3); }, TIMES); Yields (in Chrome): (1000000 times) new rect classic time in ms: 33 (1000000 times) rect classic (without new) time in ms: 368 (1000000 times) new rect classic time in ms: 35 (1000000 times) rect classic (without new) time in ms: 374 (1000000 times) new rect classic time in ms: 31 (1000000 times) rect classic (without new) time in ms: 368

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• iTextSharp Conversion from Table to pdfPTable

  - by Al.

  I have an old ASP.NET project originally done in ASP.NET 1.1 w/ iText.NET and converted to .NET 2.0 and iTextSharp 4.1.6.0. It uses lots of Table (I'm assuming pdfptable wasn't an option at the time it was created.) I am trying to convert this code to use the latest iTextSharp 5.0.0 dll and now see Table and cell have been removed. I started converting it anyway and soon found there is no equivalent to a lot of the functionality that Table offered. Mainly AddCell no longer allows a col,row setting. There are literally thousands of these calls in this code and the posibility of changing it to generate linearly row by row looks hopeless at the moment. The current code looks something like: Dim myTable As New Table(NumReq + 2, IngDS.Tables(0).Rows.Count + 3) myTable.SetWidths(Width) myTable.Width = 100 myTable.Padding = 2 myCell = New Cell(New Phrase("Some Text", New iTextSharp.text.Font(iTextSharp.text.Font.HELVETICA, 8, iTextSharp.text.Font.NORMAL, iTextSharp.text.Color.BLACK))) myCell.SetHorizontalAlignment(Element.ALIGN_RIGHT) myCell.GrayFill = 0.75 myTable.AddCell(myCell, Row, Col) myCell = New Cell(New Phrase("Other Text",New iTextSharp.text.Font(iTextSharp.text.Font.HELVETICA, 8, iTextSharp.text.Font.NORMAL, iTextSharp.text.Color.BLACK))) myCell.GrayFill = 0.75 myTable.AddCell(myCell, Row, Col+1) Before I embark down that road I was hoping someone would be able to point me in a direction that I'm just totally missing that will make this conversion much more simple. Any ideas? Thanks.

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• What's the difference between isPrototypeOf and intanceof in Javascript?

  - by Steffen Heil

  Hi In some of my own older code, I use the following: Object.prototype.instanceOf = function( iface ) { return iface.prototype.isPrototypeOf( this ); }; Then I do (for example) [].instanceOf( Array ) This works, but it seems the following would do the same: [] instanceof Array Now, surly this is only a very simple example. My question therefor is: Is a instanceof b ALWAYS the same as b.prototype.isPrototypeOf(a) ? Regards, Steffen

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• wcf class implementing two operation contracts in different service contracts with same name

  - by Archie

  Hello, I have declared two service contracts as follows: [ServiceContract] public interface IContract1 { [OperationContract] double Add(int ip); } [ServiceContract] public interface IContract2 { [OperationContract] double Add(double ip); } I have a class which implements these two contracts. I have created two end points for both the contracts. But I'm not able to access the service from client code. It displays a big error when i try to update the service reference as: Metadata contains an error that cannot be resolved.... There was no endpoint listening at ... etc. I know that you can't have two OperationContracts with the same name but is it possible to have two operation contracts in different service contracts with same name but different signature? Thanks.

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• Refactoring a C# derived class with method dependancies

  - by drelihan

  Hi Folks, I want to get your opinion on this. I have a class which is derived from a base class. I don't have control over the code in the base class and it is critical to the system that I derive from it. In my class I inherite two methods that are critical to the system and are used in pretty much every function, many times. I intend to refactor this derived class and extract some classes from it - this won't be a problem. What I'm not sure about is, is it worth extracting class if I have to constantly make call backs to my main class to access the two methods (or public wrappers to the methods)??? Thanks

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• "Undefined Symbols" when inheriting from stdexcept classes

  - by Austin Hyde

  Here is an exception defined in <stdexcept>: class length_error : public logic_error { public: explicit length_error(const string& __arg); }; Here is my exception: class rpn_expression_error : public logic_error { public: explicit rpn_expression_error(const string& __arg); }; Why do I get this error when <stdexcept> does not? Undefined symbols: rpn_expression_error::rpn_expression_error(/*string*/ const&), referenced from: ... ld: symbol(s) not found

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• Custom array class with assotiated objects

  - by FancyDancy

  I have a simple structure, it's just an array of model's objects. For example, it's a users with books. @books = Book.find(:all, :include = :users) I need to check, does user have a book? I have written a helper method: def has_book?(user_id) @books.select{|b| b.user_id == user_id}.any? end Then, i need to get only books from selected library def in_library(n) @books.select{|b| b.library == n} end I have tried to make custom Array class: class BooksList < Array def initialize(books) self << books end # its my custom methods def has_book?(user_id) self.select{|b| b.user_id == user_id}.any? end def in_library(n) self.select{|b| b.library == n} end end It works, but i have only one problem. I can't access Book's assotiated object (user). So i can't write: @books = BookList.new(Book.find(:all, :include => :users)) @books.first.user.id # it says undefined method `user' for #<Array:0x104b43e08>

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• C++ Access derived class member from base class pointer

  - by Peter

  class Base { public: int base_int; }; class Derived : Base { public: int derived_int }; Base* basepointer; basepointer-> //Access derived_int here, is it possible? If so, then how?

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• Why can't sub-packages see package private classes?

  - by Polaris878

  Okay so, I have this project structure: package A.B class SuperClass (this class is marked package private) package A.B.C class SubClass (inherits from super class) I'd rather not make SuperClass publicly visible... It is really just a utility class for this specific project (A.B). It seems to me that SubClass should be able to see SuperClass, because package A.B.C is a subpackage of A.B... but this is not the case. What would be the best way to resolve this issue? I don't think it makes sense to move everything in A.B.C up to A.B or move A.B down to A.B.C... mainly because there will probably be an A.B.D which inherits from stuff in A.B as well... I'm a bit new to Java, so be nice :D (I'm a C++ and .NET guy)

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• STI and polymorphs

  - by Alexey Poimtsev

  Hi, I have problem with my code class Post < ActiveRecord::Base end class NewsArticle < Post has_many :comments, :as => :commentable, :dependent => :destroy, :order => 'created_at' end class Comment < ActiveRecord::Base belongs_to :commentable, :polymorphic => true, :counter_cache => true end And on attempt go get comments for some NewsArticle i see in logs something like Comment Load (0.9ms) SELECT "comments".* FROM "comments" WHERE ("comments"."commentable_id" = 1 and "comments"."commentable_type" = 'Post') ORDER BY created_at Strange that "commentable_type" = 'Post'. What's wrong? PS: Rails 2.3.5 && ruby 1.8.7 (2010-01-10 patchlevel 249) [i686-darwin10]

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• HTML Frameset with just one frame and a body

  - by arik-so

  Hello, I am trying to create the following layout: an HTML file with a body, that has a certain width, and a frame, that fills the rest, so, more or less like this: <frameset cols="150px,*"> <body></body> <frame src="source.html" /> </frameset> The thing is, I need the body to have a certain width, not wider, but I also need its elements to be free to move OUTSIDE the body, over the frame, without creating a scrollbar. And I really need the body to be of limited width and the frame to fill the rest. Thanks in advance! EDIT: Okay, I will try to rephrase my problem. What I need, is something that I can put in to the frameset, that is like a border, BUT that is rendered on the main page, and not from a source, something where I can write directly and whose elements can overlap the other frame. I have tried using <noframes> but to no avail...

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• How to have a policy class implement a virtual function?

  - by dehmann

  I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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• How to use derived class shared variables in shared methods of base class

  - by KoolKabin

  Hi guys, I am trying to add shared members in derived classes and use that values in base classes... I have base class DBLayer public shared function GetDetail(byval UIN as integer) dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin) .... end function end class my derived class class User inherits dblayer public shared tabledname as string = "users" end class class item inherits dblayer public shared tabledname as string = "item" end class class category inherits dblayer public shared tabledname as string = "category" end class currently there is error using the tablename variable of derived class in base class but i want to use it... coz i dun know other techniques... if other solutions are better then u can post it or u can say how can i make it work? confused...

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• How do you declare an interface in C++?

  - by Aaron Fischer

  How do I setup a class that represents an interface? Is this just an abstract base class?

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• How to pull specific directory with git

  - by user281521

  hello, I have a project with git, and I just want to clone or pull a specific directory, like myproject/javascript just like subversion does. make some changes, commit and push back again. It's possible?

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• Implementation question involving implementing an interface

  - by Vivin Paliath

  I'm writing a set of collection classes for different types of Trees. I'm doing this as a learning exercise and I'm also hoping it turns out to be something useful. I really want to do this the right way and so I've been reading Effective Java and I've also been looking at the way Joshua Bloch implemented the collection classes by looking at the source. I seem to have a fair idea of what is being done, but I still have a few things to sort out. I have a Node<T> interface and an AbstractNode<T> class that implements the Node interface. I then created a GenericNode<T> (a node that can have 0 to n children, and that is part of an n-ary tree) class that extends AbstractNode<T> and implements Node<T>. This part was easy. Next, I created a Tree<T> interface and an AbstractTree<T> class that implements the Tree<T> interface. After that, I started writing a GenericTree<T> class that extends AbstractTree<T> and implements Tree<T>. This is where I started having problems. As far as the design is concerned, a GenericTree<T> can only consist of nodes of type GenericTreeNode<T>. This includes the root. In my Tree<T> interface I have: public interface Tree<T> { void setRoot(Node<T> root); Node<T> getRoot(); List<Node<T>> postOrder(); ... rest omitted ... } And, AbstractTree<T> implements this interface: public abstract class AbstractTree<T> implements Tree<T> { protected Node<T> root; protected AbstractTree() { } protected AbstractTree(Node<T> root) { this.root = root; } public void setRoot(Node<T> root) { this.root = root; } public Node<T> getRoot() { return this.root; } ... rest omitted ... } In GenericTree<T>, I can have: public GenericTree(Node<T> root) { super(root); } But what this means is that you can create a generic tree using any subtype of Node<T>. You can also set the root of a tree to any subtype of Node<T>. I want to be able to restrict the type of the node to the type of the tree that it can represent. To fix this, I can do this: public GenericTree(GenericNode<T> root) { super(root); } However, setRoot still accepts a parameter of type Node<T>. Which means a user can still create a tree with the wrong type of root node. How do I enforce this constraint? The only way I can think of doing is either: Do an instanceof which limits the check to runtime. I'm not a huge fan of this. Remove setRoot from the interface and have the base class implement this method. This means that it is not part of the contract and anyone who wants to make a new type of tree needs to remember to implement this method. Is there a better way? The second question I have concerns the return type of postOrder which is List<Node<T>>. This means that if a user is operating on a GenericTree<T> object and calls postOrder, he or she receives a list that consists of Node<T> objects. This means when iterating through (using a foreach construct) they would have perform an explicit cast to GenericNode<T> if they want to use methods that are only defined in that class. I don't like having to place this burden on the user. What are my options in this case? I can only think of removing the method from the interface and have the subclass implement this method making sure that it returns a list of appropriate subtype of Node<T>. However, this once again removes it from the contract and it's anyone who wants to create a new type of tree has to remember to implement this method. Is there a better way?

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• How to design this class hierarchy?

  - by devoured elysium

  I have defined an Event class: Event and all the following classes inherit from Event: AEvent BEvent CEvent DEvent Now, with the info I gather from all these Event classes, I will make a chart. With AEvent and BEvent, I will generate points for that chart, while with CEvent and DEvent I will paint certain regions of the chart. Now, how should I signal this in my class hierarchy? Should I make AEvent and BEvent inherit from PointEvent while CEvent and DEvent inherit from RegionEvent, being that both RegionEvent and PointEvent inherit from Event? Should I add a field with an Enum to Event with 2 values, Point and Region, and each of the child classes set their value to it? Should I use some kind of pattern here? Which one? Thanks.

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• Java: why does extending need an empty constructor?

  - by HH

  I have classes SearchToUser and getFilesToWord. GetFilesToWord must inherit SearchToUser fields. Extending works if an empty construction in SearchToUser-class, otherwise: cannot find symbol symbol : constructor SearchToUser() location: class SearchToUser public class GetFilesToWord extends SearchToUser{ ^ 1 error make: *** [all] Error 1 I cannot understand why the empty constructor is required for extending.

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• Can a class inherit from LambdaExpression in .NET? Or is this not recommended?

  - by d.

  Consider the following code (C# 4.0): public class Foo : LambdaExpression { } This throws the following design-time error: Foo does not implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) There's absolutely no problem with public class Foo : Expression { } but, out of curiosity and for the sake of learning, I've searched in Google System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) and guess what: zero results returned (when was the last time you saw that?). Needless to say, I haven't found any documentation on this method anywhere else. As I said, one can easily inherit from Expression; on the other hand LambdaExpression, while not marked as sealed (Expression<TDelegate> inherits from it), seems to be designed to prevent inheriting from it. Is this actually the case? Does anyone out there know what this method is about? EDIT (1): More info based on the first answers - If you try to implement Accept, the editor (C# 2010 Express) automatically gives you the following stub: protected override Expression Accept(System.Linq.Expressions.ExpressionVisitor visitor) { return base.Accept(visitor); } But you still get the same error. If you try to use a parameter of type StackSpiller directly, the compiler throws a different error: System.Linq.Expressions.Compiler.StackSpiller is inaccessible due to its protection level. EDIT (2): Based on other answers, inheriting from LambdaExpression is not possible so the question as to whether or not it is recommended becomes irrelevant. I wonder if, in cases like this, the error message should be Foo cannot implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) because [reasons go here]; the current error message (as some answers prove) seems to tell me that all I need to do is implement Accept (which I can't do).

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• Inheriting from the web client class

  - by robUK

  Hello, C# 2008 I am not sure how much work there is to inheriting from the web client class. Currently I am using it in my project. And I can't change to anything else. The customer would like to have a timeout after a certain period of time. The web client doesn't have this. So rather than re-invent the wheel, I am thinking of inheriting from the web client and adding this property. Do you think this is a suitable solution? Could it mean more work just to add this. What is the easiest way to go about this? Many thanks,

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• Combining multiple content types into a single search result with Drupal 6 and Views 2

  - by Chaulky

  Hi all, I need to create a somewhat advanced search functionality for my Drupal 6 site. I have a one-to-many relationship between two content types and need to search them, respecting that relationship. To make things more clear... I have content types TypeX and TypeY. TypeY has a node reference CCK field that relates it to a single node of TypeX. So, many nodes of TypeY reference the same node of TypeX. I want to use Views 2 to create a search page for these nodes. I want each search result to be a node of TypeX, along with all the nodes of TypeY that reference it. I know I could just theme the individual results and use a view to add the nodes of TypeY to the single node of TypeX... but that won't allow users to actually search TypeY... it would only search TypeX and merely display some nodes of TypeY along with it. Is there anyway to get the search to account for content in nodes of both content types, but merge the TypeY results into the "parent" node of TypeX? In database terms, it seems like I need to do a join, then filter by the search terms. But I can't figure out how to do this in Views. Thanks for any help i can get!!!

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• take values from table cells and turn into array

  - by liz

  using jquery I need to retrieve an array from table cells, format the data and pass it into a js function. the code i am using is this: var l1 = new Array(); $('table#datatable tbody td:first-child').each(function() { l1.push($(this).text()); }); this is the table fragment <tr> <th scope="row">Age: 0-4</th> <td>0</td> <td>9.7</td> </tr> <tr> <th scope="row">5-17</th> <td>23.6</td> <td>18.0</td> </tr> <tr> <th scope="row">Total 0-17</th> <td>20.6</td> <td>16.1</td> </tr> the table's id is "datatable". i want to return an array of the contents of each first td and then format it like this: 0,23.6,20.6 i am very new to using arrays...

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• Call the cast operator of template base class within the derived class

  - by yoni

  I have a template class, called Cell, here the definition: template <class T> class OneCell { ..... } I have a cast operator from Cell to T, here virtual operator const T() const { ..... } Now i have derived class, called DCell, here template <class T> class DCell : public Cell<T> { ..... } I need to override the Cell's cast operator (insert a little if), but after I need to call the Cell's cast operator. In other methods it's should be something like virtual operator const T() const { if (...) { return Cell<T>::operator const T; } else throw ... } but i got a compiler error error: argument of type 'const int (Cell::)()const' does not match 'const int' What can I do? Thank you, and sorry about my poor English.

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