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  • Composite Primary and Cardinality

    - by srini.venigalla
    I have some questions on Composite Primary Keys and the cardinality of the columns. I searched the web, but did not find any definitive answer, so I am trying again. The questions are: Context: Large (50M - 500M rows) OLAP Prep tables, not NOSQL, not Columnar. MySQL and DB2 1) Does the order of keys in a PK matter? 2) If the cardinality of the columns varies heavily, which should be used first. For example, if I have CLIENT/CAMPAIGN/PROGRAM where CLIENT is highly cardinal, CAMPAIGN is moderate, PROGRAM is almost like a bitmap index, what order is the best? 3) What order is the best for Join, if there is a Where clause and when there is no Where Clause (for views) Thanks in advance.

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  • java protected method accessibility

    - by JavaUser
    In the below code the Consumer class can access the protected method of Parent class.How is it possible since there is no relation between Parent and Consumer class.Please explain class Parent { public void method1(){ System.out.println("PUBLIC METHOD"); } private void method2(){ System.out.println("PRIVATE METHOD"); } protected void method3(){ System.out.println("PROTECTED METHOD"); } } public class Consumer { public static void main(String[] args){ Parent parentObj = new Parent(); parentObj.method1(); //parentObj.method2(); parentObj.method3(); } } Thanks

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Improve this generic abstract class

    - by Keivan
    I have the following abstract class design, I was wondering if anyone can suggest any improvements in terms of stronger enforcement of our requirements or simplifying implementing of the ControllerBase. //Dependency Provider base public abstract class ControllerBase<TContract, TType> where TType : TContract, class { public static TContract Instance { get { return ComponentFactory.GetComponent<TContract, TType>(); } } public TContract GetComponent<TContract, TType>() where TType : TContract, class { component = (TType)Activator.CreateInstance(typeof(TType), true); RegisterComponentInstance<TContract>(component); } } //Contract public interface IController { void DoThing(); } //Actual Class Logic public class Controller: ControllerBase<IController,Controller> { public void DoThing(); //internal constructor internal Controller(){} } //Usage public static void Main() { Controller.Instance.DoThing(); } The following facts should always be true, TType should always implement TContract (Enforced using a generic constraint) TContract must be an interface (Can't find a way to enforce it) TType shouldn't have public constructor, just an internal one, is there any way to Enforce that using ControllerBase? TType must be an concrete class (Didn't include New() as a generic constrain since the constructors should be marked as Internal)

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  • populate object graph from database

    - by Rama
    Hi, I would like to know the best way to populate an object that has a collection of child objects and each child object may inturn have a collection of objects, from database without making multiple calls to the database to get child objects for each object. basically in hierarchical format something like for example a customer has orders and each order has order items. is it best to retrieve the data in xml format (SQL server 2005), or retrieve a dataset by joining the related tables together and then map that the data to the object? thanks in advance for your help.

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  • jQuery find events handlers registered with an object

    - by ages04
    I need to find which event handlers an object has registered. eg. $("#el").click(function(){...}); $("#el").mouseover(function(){...}); Is there anyway I can use a function to find out that- $("#el") has click and mouseover registered and possibly iterate over the event handlers. If not a jQuery Object can we find this on a plain DOM object?

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  • How to access parent window variables from object

    - by Pickle
    I've got an XHTML 1.1 Strict document that is loading another XHTML 1.1 document in an <object> element (as <iframe> isn't part of the XHTML 1.1 spec). I'm having trouble in IE8 (don't care about 6 or 7) with accessing a javascript variable, Lightbox, in the parent window, from the document loaded in the <object>. In Firefox and everywhere I've seen online, I can just use window.parent.Lightbox. In IE8 however, I get it being undefined. window.parent does give me an object but it doesn't have my Lightbox variable. I've also tried window.Lightbox, window.top.Lightbox, and window.top.document.Lightbox, but all return undefined. I should mention I'm using Javascript to set the data property of the <object> - but I don't see how that could affect anything relevant. What Javascript Fu do I need to do to be able to access my Lightbox variable?

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  • Unserializing an API return object (PHP/Ebay API)

    - by DavidYell
    I have been working with the Ebay api for a project and have found it great. I have however found a problem now, more PHP related. When I read my items from Ebay, I store a bunch of details in the database. Currently, just for the sake of it really, I serialize the whole return object and store it in the database in a related table. The idea being, that when I display my information, I have all the details to hand should I need them. The problem arises in that the pricing information is always in a sub object. [ConvertedAdjustmentAmount] => __PHP_Incomplete_Class Object ( [__PHP_Incomplete_Class_Name] => eBayAmountType [_] => 0 [currencyID] => USD ) As you can see when I unserialize my object, my cunning plan falls foul of the Incomplete class problem. I have checked the following question, without success. http://stackoverflow.com/questions/965611/forcing-access-to-php-incomplete-class-object-properties The main issue lies, as far as I can see, in that the price class is stored in the Ebay api, so how do I recreate it? I have been reading this page, http://uk3.php.net/manual/en/function.unserialize.php and trying to figure out, unserialize_callback_func which I can't figure out either, so any help would be appreciated!

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  • Define an empty array in Perl class new()

    - by Laimoncijus
    Hi, I am just beginner with Perl, so if it sounds stupid - sorry for that :) My problem is - I am trying to write a class, which has an empty array, defined in constructor of a class. So I am doing this like this: package MyClass; use strict; sub new { my ($C) = @_; my $self = { items => () }; bless $self, ref $C || $C; } sub get { return $_[0]->{items}; } 1; Later I am testing my class with simple script: use strict; use Data::Dumper; use MyClass; my $o = MyClass->new(); my @items = $o->get(); print "length = ", scalar(@items), "\n", Dumper(@items); And while running the script I get following: $ perl my_test.pl length = 1 $VAR1 = undef; Why am I doing wrong what causes that I get my items array filled with undef? Maybe someone could show me example how the class would need to be defined so I would not get any default values in my array? Thanks!

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  • Listen to any change in the values of an Object in Actionscript

    - by Ali
    Hi All, I have an Object in actionscript which has a few dozens of properties each of which is defined to be bindable and has its own change event. I would like to listen to any changes made to this object without having to add a listener to all of its properties. Is there a way in actionscript using which I can listen to any change in the values of an Object ? Thanks, -A

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  • Resources for learning how to better read code

    - by rsteckly
    Hi, I recently inherited a large codebase and am having to read it. The thing is, I've usually been the dev starting a project. As a result, I don't have a lot of experience reading code. My reaction to having to read a lot of code is, well, umm to rewrite it. But I need to bring myself up to speed quickly and build on top of an existing system. Do other people have techniques they've learned to absorb a code base? At this point, I'm just reading through the code. I've tried generating UML diagrams using UModel. They're so big they won't print cleanly and when I zoom in, I really do lose the perspective of seeing all the relationships. How have other people dealt with this problem?

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • POST serialized JSON object to a Coldfusion remote method instead of using FORM

    - by zarko.susnjar
    I have javascript object which consists of complex array of structures with nested structures of other javascript objects created dynamicaly on page etc. long story. I can't use form since my vars would be like 2_34_x_y_foo_bar_235423 due to the nature of UI. When I send that stringified object using GET .ajax request to a remote cfc method everything runs ok until JSON becomes 4000+ chars long, and usually it will be longer then that. When I use POST .ajax, I get 302 status and redirection to cfcexplorer. Is there some way I could "attach" object to a form and send my data as form submit, or some way to send JSON object as it is now using ajax call?

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • How do I correct feature envy in this case?

    - by RMorrisey
    I have some code that looks like: class Parent { private Intermediate intermediateContainer; public Intermediate getIntermediate(); } class Intermediate { private Child child; public Child getChild() {...} public void intermediateOp(); } class Child { public void something(); public void somethingElse(); } class Client { private Parent parent; public void something() { parent.getIntermediate().getChild().something(); } public void somethingElse() { parent.getIntermediate().getChild().somethingElse(); } public void intermediate() { parent.getIntermediate().intermediateOp(); } } I understand that is an example of the "feature envy" code smell. The question is, what's the best way to fix it? My first instinct is to put the three methods on parent: parent.something(); parent.somethingElse(); parent.intermediateOp(); ...but I feel like this duplicates code, and clutters the API of the Parent class (which is already rather busy). Do I want to store the result of getIntermediate(), and/or getChild(), and keep my own references to these objects?

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  • Reading object tree from file into Python

    - by jjkparker
    I have a Python app that contains an object structure that the user can manipulate. What I want to do is allow the user to create a file declaring how the object structure should be created. For example, I would like the user to be able to create the following file: foo.bar.baz = true x.y.z = 12 and for my app to then create that object tree automatically. What's the best way to do something like this?

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  • Compromising design & code quality to integrate with existing modules

    - by filip-fku
    Greetings! I inherited a C#.NET application I have been extending and improving for a while now. Overall it was obviously a rush-job (or whoever wrote it was seemingly less competent than myself). The app pulls some data from an embedded device & displays and manipulates it. At the core is a communications thread in the main application form which executes a 600+ lines of code method which calls functions all over the place, implementing a state machine - lots of if-state-then-do type code. Interaction with the device is done by setting the state/mode globally and letting the thread do it's thing. (This is just one example of the badness of the code - overall it is not very OO-like, it reminds of the style of embedded C code the device firmware is written in). My problem is that this piece of code is central to the application. The software, communications protocol or device firmware are not documented at all. Obviously to carry on with my work I have to interact with this code. What I would like some guidance on, is whether it is worth scrapping this code & trying to piece together something more reasonable from the information I can reverse engineer? I can't decide! The reason I don't want to refactor is because the code already works, and changing it will surely be a long, laborious and unpleasant task. On the flip side, not refactoring means I have to sometimes compromise the design of other modules so that I may call my code from this state machine! I've heard of "If it ain't broke don't fix it!", so I am wondering if it should apply when "it" is influencing the design of future code! Any advice would be appreciated! Thanks!

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  • Where to start when doing a Domain Model?

    - by devoured elysium
    Let's say I've made a list of concepts I'll use to draw my Domain Model. Furthermore, I have a couple of Use Cases from which I did a couple of System Sequence Diagrams. When drawing the Domain Model, I never know where to start from: Designing the model as I believe the system to be. This is, if I am modelling a the human body, I start by adding the class concepts of Heart, Brain, Bowels, Stomach, Eyes, Head, etc. Start by designing what the Use Cases need to get done. This is, if I have a Use Case which is about making the human body swallow something, I'd first draw the class concepts for Mouth, Throat, Stomatch, Bowels, etc. The order in which I do things is irrelevant? I'd say probably it'd be best to try to design from the Use Case concepts, as they are generally what you want to work with, not other kind of concepts that although help describe the whole system well, much of the time might not even be needed for the current project. Is there any other approach that I am not taking in consideration here? How do you usually approach this? Thanks

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  • Modules vs. Classes and their influence on descendants of ActiveRecord::Base

    - by Chris
    Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario: class Product < ActiveRecord::Base has_many(:prices) # define private helper methods end module PrintProduct attr_accessor(:isbn) # override methods in ActiveRecord::Base end class Book < Product include PrintProduct end Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior: After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found. Why is that? Book is a direct descendant of Product! More interesting is the following.. As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such: class Product < ActiveRecord::Base end class PrintProduct < Product end class Book < PrintProduct end All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module. Any insight would be appreciated. I'm dying to know why these errors are occurring!

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