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  • How to Correct & Improve the Design of this Code?

    - by DaveDev
    HI Guys, I've been working on a little experiement to see if I could create a helper method to serialize any of my types to any type of HTML tag I specify. I'm getting a NullReferenceException when _writer = _viewContext.Writer; is called in protected virtual void Dispose(bool disposing) {/*...*/} I think I'm at a point where it almost works (I've gotten other implementations to work) and I was wondering if somebody could point out what I'm doing wrong? Also, I'd be interested in hearing suggestions on how I could improve the design? So basically, I have this code that will generate a Select box with a number of options: // the idea is I can use one method to create any complete tag of any type // and put whatever I want in the content area <% using (Html.GenerateTag<SelectTag>(Model, new { href = Url.Action("ActionName") })) { %> <%foreach (var fund in Model.Funds) {%> <% using (Html.GenerateTag<OptionTag>(fund)) { %> <%= fund.Name %> <% } %> <% } %> <% } %> This Html.GenerateTag helper is defined as: public static MMTag GenerateTag<T>(this HtmlHelper htmlHelper, object elementData, object attributes) where T : MMTag { return (T)Activator.CreateInstance(typeof(T), htmlHelper.ViewContext, elementData, attributes); } Depending on the type of T it'll create one of the types defined below, public class HtmlTypeBase : MMTag { public HtmlTypeBase() { } public HtmlTypeBase(ViewContext viewContext, params object[] elementData) { base._viewContext = viewContext; base.MergeDataToTag(viewContext, elementData); } } public class SelectTag : HtmlTypeBase { public SelectTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("select"); //base.MergeDataToTag(viewContext, elementData); } } public class OptionTag : HtmlTypeBase { public OptionTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("option"); //base.MergeDataToTag(viewContext, _elementData); } } public class AnchorTag : HtmlTypeBase { public AnchorTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("a"); //base.MergeDataToTag(viewContext, elementData); } } all of these types (anchor, select, option) inherit from HtmlTypeBase, which is intended to perform base.MergeDataToTag(viewContext, elementData);. This doesn't happen though. It works if I uncomment the MergeDataToTag methods in the derived classes, but I don't want to repeat that same code for every derived class I create. This is the definition for MMTag: public class MMTag : IDisposable { internal bool _disposed; internal ViewContext _viewContext; internal TextWriter _writer; internal TagBuilder _tag; internal object[] _elementData; public MMTag() {} public MMTag(ViewContext viewContext, params object[] elementData) { } public void Dispose() { Dispose(true /* disposing */); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!_disposed) { _disposed = true; _writer = _viewContext.Writer; _writer.Write(_tag.ToString(TagRenderMode.EndTag)); } } protected void MergeDataToTag(ViewContext viewContext, object[] elementData) { Type elementDataType = elementData[0].GetType(); foreach (PropertyInfo prop in elementDataType.GetProperties()) { if (prop.PropertyType.IsPrimitive || prop.PropertyType == typeof(Decimal) || prop.PropertyType == typeof(String)) { object propValue = prop.GetValue(elementData[0], null); string stringValue = propValue != null ? propValue.ToString() : String.Empty; _tag.Attributes.Add(prop.Name, stringValue); } } var dic = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); var attributes = elementData[1]; if (attributes != null) { foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(attributes)) { object value = descriptor.GetValue(attributes); dic.Add(descriptor.Name, value); } } _tag.MergeAttributes<string, object>(dic); _viewContext = viewContext; _viewContext.Writer.Write(_tag.ToString(TagRenderMode.StartTag)); } } Thanks Dave

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  • Concurrent usage of table causing issues

    - by Sven
    Hello In our current project we are interfacing with a third party data provider. They need to insert data in a table of ours. This inserting can be frequent every 1 min, every 5min, every 30, depends on the amount of new data they need to provide. The use the isolation level read committed. On our end we have an application, windows service, that calls a webservice every 2 minutes to see if there is new data in this table. Our isolation level is repeatable read. We retrieve the records and update a column on these rows. Now the problem is that sometimes this third party provider needs to insert a lot of data, let's say 5000 records. They do this per transaction (5rows per transaction), but they don't close the connection. They do one transaction and then the next untill all records are inserted. This caused issues for our process, we receive a timeout. If this goes on for a long time the database get's completely unstable. For instance, they maybe stopped, but the table somehow still stays unavailable. When I try to do a select on the table, I get several records but at a certain moment I don't get any response anymore. It just says retrieving data but nothing comes anymore until I get a timeout exception. Only solution is to restart the database and then I see the other records. How can we solve this. What is the ideal isolation level setting in this scenario?

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  • C++ Dynamic object construction

    - by Rajesh Subramanian
    I have a base class, class Msg { ParseMsg() { ParseMsgData(); ParseTrailer(); } virtual void ParseMsgData() = 0; ParseTrailer(); }; and derived classes, class InitiateMsg { void ParseMsgData() { ... } }; class ReadOperationMsg { void ParseMsgData() { ... } }; class WriteOperationMsg { void ParseMsgData() { ... } }; and the scenario is below, void UsageFunction(string data) { Msg* msg = ParseHeader(data); ParseMsg } Msg* ParseHeader(string data) { Msg *msg = NULL; .... switch() { case 1: msg = new InitiateMsg(); break; case 2: msg = new ReadOperationMsg{(); break; case 3: msg = new WriteOperationMsg{(); break; .... } return msg; } based on the data ParseHeader method will decide which object has to be created, So I have implemented ParseHeader function outside the class where I am using. How can I make the ParseHeader function inside the Msg class and then use it? In C# the same is achieved by defining ParseHeader method as static with in class and use it from outside,

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  • Does string inherits from Object in Javascript?

    - by Morgan Cheng
    Is Object the base class of all objects in Javascript, just like other language such as Java & C#? I tried below code in Firefox with Firebug installed. var t = new Object(); var s1 = new String('str'); var s2 = 'str'; console.log(typeof t); console.log(typeof s1); console.log(typeof s2); The console output is object object string So, s1 and s2 are of diffeent type?

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  • [MySQL] Load data from .csv applying regex before insert into table

    - by Gabriel L. Oliveira
    I know that there is a code to import .csv data into a mysql table, and I'm using this one: LOAD DATA INFILE "file.csv" INTO TABLE foo FIELDS TERMINATED BY "," LINES TERMINATED BY "\\r\\n"; The data inside this .csv are lines like this example: 08/e0/Breast_Cancer_Res_2001_Nov_2_3(1)_55-60.tar.gz Breast Cancer Res. 2001 Nov 2; 3(1):55-60 PMC13900 b0/ac/Breast_Cancer_Res_2001_Nov_9_3(1)_61-65.tar.gz Breast Cancer Res. 2001 Nov 9; 3(1):61-65 PMC13901 I just want the first part (the .tar.gz path), always on the pattern (letter or number)(letter or number) / (letter or number)(letter or number)/... and the part starting by 'PMC', always on the pattern PMC(number...) where 'number' means a number between 0 to 9 and a letter means a letter between a to z (both upper and lower case) So, applying the LOAD DATA, and the regex, and inserting the result entries on my sql table, the result table should be: 1 08/e0/Breast_Cancer_Res_2001_Nov_2_3(1)_55-60.tar.gz PMC13900 2 b0/ac/Breast_Cancer_Res_2001_Nov_9_3(1)_61-65.tar.gz PMC13901 What should be the SQL command to do all this?

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  • Mapping element via joining table with NHibernate

    - by NhibernateIdiot
    This is stuff ive done lots of times before but my mind is just blanking at the moment, i will try and give a simple overview of my current situation. I currently have 3 tables as shown below: Office > id, name Person > id, name Office_Personnel > office_id, person_id I then have a model for Person (id, name) and Office, however the Office model contains personnel information: public class Office { int Id {get;set;} string Name {get;set;} ICollection<Person> Personnel {get;set;} } Mapping person is easy, but now im a bit stumped as to why office wont map properly. I chose to use a set when I was mapping the Personnel as there shouldn't be any duplicates, however it doesn't seem to work as I would expect... <set name="Personnel" table="office_personnel" cascade="all"> <key column="office_id" /> <one-to-many class="Person"/> </set> Now one thing that strikes me as odd is that there is no indication as to what person should be binding to (person_id). It keeps trying to find *office_id* column within the Person table. I'm sure this is just some simple problem and im being an idiot, but any help would be great! On a side note, I was weighing up if I should even bother having a middle man table, as I could directly put an Office_Id column within the Person table, but im not 100% sure if in my real project the Person class could be in multiple Offices further down the line...

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  • Actionscript - combining AS2 assets into a single SWF

    - by Justin Bachorik
    Hi guys, I have a flash project that I'm trying to export as a single SWF. There's a main SWF file that loads about 6 other SWFs, and both the main and the child SWFs reference other external assets (images, sounds, etc). I'd like to package everything as a single .swf file so I don't have to tote the other assets around with the .swf. All the coding is done in the timeline, but the assets haven't been imported into the Flash Authoring environment and I don't have time to do that right now (there are too many references to them everywhere). I'm hoping that there's just an option I'm missing that allows this sort of packaged export, but I haven't found anything like that. I don't have access to Flex or mxmlc (and as the AS is timeline-based, they wouldn't necessarily help me). Any thoughts? Thanks! PS...if there's no way of doing exactly what I'm saying, I could deal with having all the assets in a "assets" folder or something like that, so I'd just be toting around main.swf and an assets folder. The problem here is that all the references to the assets assume that they're in the same folder as the main.swf file, so everything's assumed to be local...is there a way to change the scope of all external references in Flash (so, for example, all local references in the code are actually searched in /assets)?

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  • Inserting Row in Table inside Form tag autosubmitting in firefox/chrome

    - by user1861489
    I have a form that will have dynamic elements inserted with javascript and am experiencing some strange behavior. When I click the button to add another element to the table in the form, it adds the element but seems to to a form post immediately (without intending to submit the form yet) I have created a simplified example of the page that has the same behavior. the first table element is created on page load and subsequent elements are added when clicking on the button. this form works successfully in IE. does anyone have an idea of how to prevent this behavior? here is the code sample. <!DOCTYPE html> <html> <head> <title>Test Creating Form</title> <meta http-equiv="Content-type" content="text/html;charset=UTF-8"> <style type="text/css"> td{font-family:verdana;} </style> <script type="text/javascript"> var counter = 0; function makeTitle(title){ if(counter){ title += " " + counter; } counter++; var tbl = document.getElementById('tbl'); var tr = tbl.insertRow(-1) var td1 = tr.insertCell(-1); td1.innerHTML = title; } function load1(){ makeTitle('Primary Specimen'); } </script> </head> <body onload="load1();"> <form action="formtest.htm" method="post" name="testForm" id="testForm"> <table id="tbl" border="1"></table> <button onclick="makeTitle('Alternate Specimen')" id="clone" >Add Another Specimen</button> </form> </body> </html>

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  • How to have variables with dynamic data types in Java?

    - by Nazgulled
    Hi, I need to have a UserProfile class that it's just that, a user profile. This user profile has some vital user data of course, but it also needs to have lists of messages sent from the user friends. I need to save these messages in LinkedList, ArrayList, HashMap and TreeMap. But only one at a time and not duplicate the message for each data structure. Basically, something like a dynamic variable type where I could pick the data type for the messages. Is this, somehow, possible in Java? Or my best approach is something like this? I mean, have 2 different classes (for the user profile), one where I host the messages as Map<K,V> (and then I use HashMap and TreeMap where appropriately) and another class where I host them as List<E> (and then I use LinkedList and ArrayList where appropriately). And probably use a super class for the UserProfile so I don't have to duplicate variables and methods for fields like data, age, address, etc... Any thoughts?

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  • javascript function object's inheritFrom method

    - by gawpertron
    I've come across this.inheritFrom that enables you to inherit from a super class. var superClass = function() { this.foo = 'foo'; this.bar = 'bar'; } var subClass = function() { this.inheritFrom = superClass; this.inheritFrom(); this.myFunction = function() { return this.foo; }; } I've looked in Mozilla and MSDN, but I can't seem to find it documented any where. As far as I can see it works in IE6 and Firefox 3. Any reason why it wouldn't be documented?

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  • Why can a public class not inherit from a less visible one?

    - by Dan Tao
    I apologize if this question has been asked before. I've searched SO somewhat and wasn't able to find it. I'm just curious what the rationale behind this design was/is. Obviously I understand that private/internal members of a base type cannot, nor should they, be exposed through a derived public type. But it seems to my naive thinking that the "hidden" parts could easily remain hidden while some base functionality is still shared and a new interface is exposed publicly. I'm thinking of something along these lines: Assembly X internal class InternalClass { protected virtual void DoSomethingProtected() { // Let's say this method provides some useful functionality. // Its visibility is quite limited (only to derived types in // the same assembly), but at least it's there. } } public class PublicClass : InternalClass { public void DoSomethingPublic() { // Now let's say this method is useful enough that this type // should be public. What's keeping us from leveraging the // base functionality laid out in InternalClass's implementation, // without exposing anything that shouldn't be exposed? } } Assembly Y public class OtherPublicClass : PublicClass { // It seems (again, to my naive mind) that this could work. This class // simply wouldn't be able to "see" any of the methods of InternalClass // from AssemblyX directly. But it could still access the public and // protected members of PublicClass that weren't inherited from // InternalClass. Does this make sense? What am I missing? }

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  • Get derived class type from a base's class static method

    - by Marco Bettiolo
    Hi, i would like to get the type of the derived class from a static method of its base class. How can this be accomplished? Thanks! class BaseClass { static void Ping () { Type t = this.GetType(); // should be DerivedClass, but it is not possible with a static method } } class DerivedClass : BaseClass {} // somewhere in the code DerivedClass.Ping();

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  • Why can't I create an abstract constructor on an abstract C# class?

    - by Anthony D
    I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one. public abstract class A { abstract A(int a, int b); } However I get a message saying the abstract modifier is invalid on this item. My goal was to force some code like this. public class B : A { public B(int a, int b) : base(a, b) { //Some other awesome code. } } This is all C# .NET code. Can anyone help me out? Update 1 I wanted to add some things. What I ended up with was this. private A() { } protected A(int a, int b) { //Code } That does what some folks are saying, default is private, and the class needs to implement a constructor. However that doesn't FORCE a constructor with the signature A(int a, int b). public abstract class A { protected abstract A(int a, int b) { } } Update 2 I should be clear, to work around this I made my default constructor private, and my other constructor protected. I am not really looking for a way to make my code work. I took care of that. I am looking to understand why C# does not let you do this.

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  • Help on MySQL table indexing when GROUP BY is used in a query

    - by Silver Light
    Thank you for your attention. There are two INNODB tables: Table authors id INT nickname VARCHAR(50) status ENUM('active', 'blocked') about TEXT Table books author_id INT title VARCHAR(150) I'm running a query against these tables, to get each author and a count of books he has: SELECT a. * , COUNT( b.id ) AS book_count FROM authors AS a, books AS b WHERE a.status != 'blocked' AND b.author_id = a.id GROUP BY a.id ORDER BY a.nickname This query is very slow (takes about 6 seconds to execute). I have an index on books.author_id and it works perfectly, but I do not know how to create an index on authors table, so that this query could use it. Here is how current EXPLAIN looks: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE a ALL PRIMARY,id_status_nickname NULL NULL NULL 3305 Using where; Using temporary; Using filesort 1 SIMPLE b ref key_author_id key_author_id 5 a.id 2 Using where; Using index I've looked at MySQL manual on optimizing queries with group by, but could not figure out how I can apply it on my query. I'll appreciate any help and hints on this - what must be the index structure, so that MySQL could use it?

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  • PHP inheriting/extending a particular instance of an Object

    - by delta9
    Is there any way to force PHP to extend an existing/particular (and for that matter, already instantiated) instance of an object? This imaginary code should explain what I am wondering: class Base { public $var; function __construct($var){ $this->var = $name; } } class Extender extends Base { function __construct($parent) { parent = $parent; } } $base = new Base('yay!'); $extender = new Extender($base); echo 'Extended base var value: '.$extender->var.'<br/>'; Output (would be): Extended base var value: yay! To be clear, I am wanting to instantiate an object that extends a PARTICULAR INSTANCE of another object, one that has already been instantiated. I am aware that I can pass a reference to an object to another object (via it's constructor function) and then add it as a property of the receiving object, I'm wondering if there is a real way to do this?

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  • are Hierarchical SIngletons in Java possible?

    - by Zach H
    I've been toying with an interesting idea (No idea if I'll include it in any code, but it's fun to think about) Let's say we have a program that requires a large number of classes, all of a certain subclass. And those classes all need to be singletons. Now, we could write the singleton pattern for each of those classes, but it seems wasteful to write the same code over and over, and we already have a common base class. It would be really nice to create a getSingleton method of A that when called from a subclass, returns a singleton of the B class (cast to class A for simplicity) class A{ public A getSingleton(){ //Wizardry } } class B extends A{ } A blargh = B.getSingleton() A gish = B.getSingleton() if(A == B) System.out.println("It works!") It seems to me that the way to do this would be to recognize and call B's default constructor (assuming we don't need to pass anything in.) I know a little of the black magic of reflection in Java, but i'm not sure if this can be done. Anyone interested in puzzling over this?

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  • Storing multiple discarded datas in a single variable using a string accumulator

    - by dan
    For an assignment for my intro to python course, we are to write a program that generates 100 sets of x,y coordinates. X must be a float between -100.0 and 100.0 inclusive, but not 0. Y is Y = ((1/x) * 3070) but if the absolute value of Y is greater than 100, both numbers must be discarded (BUT STORED) and another set generated. The results must be displayed in a table, and then after the table, the discarded results must be shown. The teacher said we should use a "string accumulator" to store the discarded data. This is what I have so far, and I'm stuck at storing the discarded data. # import random.py import random # import math.py import math # define main def main(): x = random.uniform(-100.0, 100.0) while x == 0: x = random.uniform(-100.0, 100.0) y = ((1/x) * 3070) while math.fabs(y) > 100: xDiscarded = yDiscarded = y = ((1/x) * 3070) As you can see, I run into the problem of when abs(y) 100, I'm not too sure how to store the discarded data and let it accumulate every time abs(y) 100. I'm cool with the data being stored as "351.2, 231.1, 152.2" I just don't know how to turn the variable into a string and store it. We haven't learned arrays yet so I can't do that. Any help would be much appreciated. Thanks!

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  • C# casting question: from IEnumerable to custom type

    - by Sarah Vessels
    I have a custom class called Rows that implements IEnumerable<Row>. I often use LINQ queries on Rows instances: Rows rows = new Rows { row1, row2, row3 }; IEnumerable<Row> particularRows = rows.Where<Row>(row => condition); What I would like is to be able to do the following: Rows rows = new Rows { row1, row2, row3 }; Rows particularRows = (Rows)rows.Where<Row>(row => condition); However, I get a "System.InvalidCastException: Unable to cast object of type 'WhereEnumerableIterator1[NS.Row]' to type 'NS.Rows'". I do have a Rows constructor taking IEnumerable<Row>, so I could do: Rows rows = new Rows { row1, row2, row3 }; Rows particularRows = new Rows(rows.Where<Row>(row => condition)); This seems bulky, however, and I would love to be able to cast an IEnumerable<Row> to be a Rows since Rows implements IEnumerable<Row>. Any ideas?

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  • Container<ImplementerOfIInterface> is not Container<IInterface>. Why not?

    - by Chris Simmons
    Why wouldn't DoesntWork() work below? The error is: Cannot implicitly convert type 'List' to 'IEnumerable'. An explicit conversion exists (are you missing a cast?). I know this is something about generic/templates I'm not getting, but List is IEnumerable and Implementer is an IInterface. I don't see why this needs to be casted (or if it really can be). public interface IInterface { // ... } public class Implementer : IInterface { // ... } IEnumerable<IInterface> DoesntWork() { List<Implementer> result = new List<Implementer>(); return result; }

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  • Class lookup structure array in C++

    - by wyatt
    I'm trying to create a structure array which links input strings to classes as follows: struct {string command; CommandPath cPath;} cPathLookup[] = { {"set an alarm", AlarmCommandPath}, {"send an email", EmailCommandPath}, {"", NULL} }; which will be used as follows: CommandPath *cPath = NULL; string input; getline(cin, input); for(int i = 0; cPathLookup[i] != ""; i++) { if(cPathLookup[i].command == input) cPath = new cPathLookup[i].cPath; } Obviously, this code is meaningless, but I think my intention is apparent - depending on input, I'd like cPath to be initialized as either a new AlarmCommandPath or a new EmailCommandPath. I could handle it with a function returning an instance depending on input, but a whole sequence of ifs just seems inelegant. I should also note that, in case it's not apparent and important, that AlarmCommandPath and EmailCommandPath are derived from CommandPath, and CommandPath is an abstract class. Thanks for any help you can offer. EDIT: I just noticed that, in spite of CommandPath being abstract, I have a declaration: CommandPath *cPath = NULL; in working code. Why does that compile?

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  • Ways to make (relatively) safe assumptions about the type of concrete subclasses?

    - by Kylotan
    I have an interface (defined as a abstract base class) that looks like this: class AbstractInterface { public: bool IsRelatedTo(const AbstractInterface& other) const = 0; } And I have an implementation of this (constructors etc omitted): class ConcreteThing { public: bool IsRelatedTo(const AbstractInterface& other) const { return m_ImplObject.has_relationship_to(other.m_ImplObject); } private: ImplementationObject m_ImplObject; } The AbstractInterface forms an interface in Project A, and the ConcreteThing lives in Project B as an implementation of that interface. This is so that code in Project A can access data from Project B without having a direct dependency on it - Project B just has to implement the correct interface. Obviously the line in the body of the IsRelatedTo function cannot compile - that instance of ConcreteThing has an m_ImplObject member, but it can't assume that all AbstractInterfaces do, including the other argument. In my system, I can actually assume that all implementations of AbstractInterface are instances of ConcreteThing (or subclasses thereof), but I'd prefer not to be casting the object to the concrete type in order to get at the private member, or encoding that assumption in a way that will crash without a diagnostic later if this assumption ceases to hold true. I cannot modify ImplementationObject, but I can modify AbstractInterface and ConcreteThing. I also cannot use the standard RTTI mechanism for checking a type prior to casting, or use dynamic_cast for a similar purpose. I have a feeling that I might be able to overload IsRelatedTo with a ConcreteThing argument, but I'm not sure how to call it via the base IsRelatedTo(AbstractInterface) method. It wouldn't get called automatically as it's not a strict reimplementation of that method. Is there a pattern for doing what I want here, allowing me to implement the IsRelatedTo function via ImplementationObject::has_relationship_to(ImplementationObject), without risky casts? (Also, I couldn't think of a good question title - please change it if you have a better one.)

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  • List all foreign key constraints that refer to a particular column in a specific table

    - by Sid
    I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • custom sorting or ordering a table without resorting the whole shebang

    - by fuugus
    for ten years we've been using the same custom sorting on our tables, i'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and would'nt like to have our replication replicate unnecessary entries. i had a look into nested sets, but it does'nt seem to do the job for us. base table: id | a_sort ---+------- 1 10 2 20 3 30 after inserting insert into table (a_sort) values(15) an entry at the second position. id | a_sort ---+------- 1 10 2 20 3 30 4 15 ordering the table with select * from table order by a_sort and resorting all the a_sort entries, updating at least id=(2,3,4) will of course produce the desired output id | a_sort ---+------- 1 10 4 20 2 30 3 40 the column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem. also we've found some pretty neat ways to do this task fast. only; how the heck can we reduce the updates in the db to 1 or 2 max. seems like an awfully common problem. the captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".. but this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)

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