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  • Any tips of how to handle hierarchial trees in relational model?

    - by George
    Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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  • Best ways to construct Dynamic Search Conditions for Sql

    - by CoolBeans
    I have always wondered what's the best way to achieve this task. In most web based applications you have to provide search options on many different criteria. Based on what criteria is chosen behind the scene you modify your SQL. Generally, this is how I tend to go about it:- Have a base SQL template. In the base template have conditions like this WHERE [#PRE_COND1] AND [#PRE_COND2] .. so on and so forth. So an example SQL might look something like SELECT NAME,AGE FROM PERSONS [,#TABLE2] [,#TABLE3] WHERE [#PRE_COND1] AND [#PRE_COND2] ORDER BY [#ORD_COND1] AND [#ORD_COND2] etc. During run time after figuring out the all the search criteria user has entered, I replace the [#PRE_COND1]s and [#ORD_COND1]s with the appropriate SQLs and then execute the query. I personally do not like this brute force method. However, I never came across a better approach either. How do you accomplish such tasks generally given you are either using native JDBC or Spring JDBC? It is almost like I need a C MACRO like functionality in Java to do this.

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  • How to handle injecting dependencies into rich domain models?

    - by Arne
    In a web server project with a rich domain model (application logic is in the model, not in the services) how do you handle injecting the dependencies into the model objects? What are your experiences? Do you use some form of AOP? Like Springs @Configurable annotation? Load time or build time weawing? Problems you encountered? Do you use manual injection? Then how do you handle different instantiation scenarios (creating of the objects through an library [like Hibernate], creating objects with "new" ...)? Or do you use some other way of injecting the dependencies?

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  • Java: Friendlier way to get an instance of FontMetrics

    - by Martijn Courteaux
    Hi people, Is there a friendlier way to get an instance of FontMetrics than FontMetrics fm = Graphics.getFontMetrics(Font); I hate this way because of the following example: If you want to create in a game a menu and you want all the menuitems in the center of the screen you need fontmetrics. But, mostly, menuitems are clickable. So I create an array of Rectangles and all the rectangles fits around the items, so when the mouse is pressed, I can simply use for (int i = 0; i < rects.length; i++) if (rects[i].contains(mouseX, mouseY)) { ... } But to create the rects I also need FontMetrics for their coordinates. So this mean that I have to construct all my rectangles in the paint-method of my menu. So I want a way to get the FontMetrics so I can construct the Rectangles in a method called by the constructor. Hope you understand. Thanks in advance.

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  • help me to choose between two designs

    - by alex
    // stupid title, but I could not think anything smarter I have a code (see below, sorry for long code but it's very-very simple): namespace Option1 { class AuxClass1 { string _field1; public string Field1 { get { return _field1; } set { _field1 = value; } } // another fields. maybe many fields maybe several properties public void Method1() { // some action } public void Method2() { // some action 2 } } class MainClass { AuxClass1 _auxClass; public AuxClass1 AuxClass { get { return _auxClass; } set { _auxClass = value; } } public MainClass() { _auxClass = new AuxClass1(); } } } namespace Option2 { class AuxClass1 { string _field1; public string Field1 { get { return _field1; } set { _field1 = value; } } // another fields. maybe many fields maybe several properties public void Method1() { // some action } public void Method2() { // some action 2 } } class MainClass { AuxClass1 _auxClass; public string Field1 { get { return _auxClass.Field1; } set { _auxClass.Field1 = value; } } public void Method1() { _auxClass.Method1(); } public void Method2() { _auxClass.Method2(); } public MainClass() { _auxClass = new AuxClass1(); } } } class Program { static void Main(string[] args) { // Option1 Option1.MainClass mainClass1 = new Option1.MainClass(); mainClass1.AuxClass.Field1 = "string1"; mainClass1.AuxClass.Method1(); mainClass1.AuxClass.Method2(); // Option2 Option2.MainClass mainClass2 = new Option2.MainClass(); mainClass2.Field1 = "string2"; mainClass2.Method1(); mainClass2.Method2(); Console.ReadKey(); } } What option (option1 or option2) do you prefer ? In which cases should I use option1 or option2 ? Is there any special name for option1 or option2 (composition, aggregation) ?

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  • Object Events, how do are they implemented

    - by Malfist
    Events are really awesome, and I wouldn't know what I would do without them, but they're a mystery to me. I'm talking about events in a sense, a function(s) is called if a property, or value, a special event happens. I have only the vaguest idea how these actually work. I know it's an observer pattern, but I don't truly know how it works and/or how to implement it. Can someone explain that to me?

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  • How to Execute Base Class's Method Before Implementors's Method?

    - by DaveDev
    I have the following page public partial class GenericOfflineCommentary : OfflineFactsheetBase { } where OfflineFactsheetBase is defined as public class OfflineFactsheetBase : System.Web.UI.Page { public OfflineFactsheetBase() { this.Load += new EventHandler(this.Page_Load); this.PreInit += new EventHandler(this.Page_PreInit); } protected void Page_PreInit(object sender, EventArgs e) { if (Request.QueryString["data"] != null) { this.PageData = StringCompressor.DecompressString(Request.QueryString["data"]); this.ExtractPageData(); } } } OfflineFactsheetBase has the following virtual method: public virtual void ExtractPageData() { // get stuff relevant to all pages that impmement OfflineFactsheetBase } which is implemented in all pages that impmement OfflineFactsheetBase as follows: public partial class GenericOfflineCommentary : OfflineFactsheetBase { public override void ExtractPageData() { // get stuff relevant to an OfflineCommentary page. } } Currently, only GenericOfflineCommentary's ExtractPageData() is firing. How can I modify this to first run OfflineFactsheetBase's ExtractPageData() and then GenericOfflineCommentary's? edit: I'm trying to avoid having to call base.ExtractPageData() in every implementor. Is this possible?

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  • Android & Web: What is the equivalent style for the web?

    - by Legend
    I am quite impressed by the workflow I follow when developing Android applications: Define a layout in an xml file and then write all the code in a code-behind style. Is there an equivalent style for the web? I mean, with a predefined list of widgets that can be defined using a markup language and then control them using code? I have come across Google's Web Toolkit that does something like this but I'd like to hear what other's think as well.

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  • suggestions on syntax to express mathematical formula concisely

    - by aaa
    hello. I am developing functional domain specific embedded language within C++ to translate formulas into working code as concisely and accurately as possible. I post prototype in the comment, it is about 2 hundred lines long. Right now my language looks something like this (well, actually is going to look like): // implies two nested loops j=0:N, i=0,j (range(i) < j < N)[T(i,j) = (T(i,j) - T(j,i))/e(i+j)]; // implies summation over above expression sum(range(i) < j < N))[(T(i,j) - T(j,i))/e(i+j)]; I am looking for possible syntax improvements/extensions or just different ideas about expressing mathematical formulas as clearly and precisely as possible (in any language, not just C++). Can you give me some syntax examples relating to my question which can be accomplished in your language of choice which consider useful. In particular, if you have some ideas about how to translate the above code segments, I would be happy to hear them. Thank you just to clarify and give actual formula, my short-term goal is to express the following expression concisely where values in <> are already computed as 4-dimensional array

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  • CSS Sprite for images which have vertical as well as horizontal repeats

    - by Rachel
    I have four images, one of which has background repeat property in horizontal direction and three of which have background repeat in vertical direction. I have different CSS classes which currently uses this images as under: .sb_header_dropdown { background: url(images/shopping_dropdown_bg.gif) repeat-y top left; padding: 8px 3px 8px 15px; } .shopping_basket_dropdown .sb_body { background: url(images/shopping_dropdown_body_bg.png) repeat-y top left; margin: 0; padding: 5px 9px 5px 8px; position: relative; z-index: 99999; } .checkout_cart .co_header_left { background: url(images/bg.gif) repeat-x 0 -150px; overflow: hidden; padding-left: 3px; } .sb_dropdown_footer { background: url(images/shopping_dropdown_footer_bg.png) repeat-y top left; clear: both; height: 7px; font-size: 0; } So here am making 4 HTTP Request and I want to implement CSS Sprite for all 4 images such that I can reduce the number of HTTP Request from 4 to 1, also thing to keep in mind is that here we have background repeat for all 4 images, either on x-direction or on y-direction and so how should sprite be created and how it can be used in the CSS to reduce the number of HTTP request. I hope this question is clear.

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  • PHP: Star rating system concept?

    - by Prashant
    I am using PHP/MYSQL/JQUERY. I have a site which have news section. On news details page, I want to add star rating system which will allow user to rate the news story. I am using this jquery rating system http://www.fyneworks.com/jquery/star-rating/ Now, I am not getting what will be the database structure and then what I need to code in PHP. I need what logic will be applied for this, like if 1000 people voted for the article, some given rating as 2 or 3 or1 or 5. Then Where I should be storing (db structure) this all and what I'll calculate (in php code). If someone has any article which shows this concept please provide. Please help, to understand the logic and concept of this. Thanks!

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  • Is it okay to rely on javascript for menu layout?

    - by Ryan
    I have a website template where I do not know the number of menu items or the size of the menu items that will be required. The js below works exactly the way I want it to, however this is the most js I've every written. Are there any disadvantages or potential problems with this method that I'm not aware of because I'm a js beginner? I'm currently manually setting the padding for each site. Thank you! var width_of_text = 0; var number_of_li = 0; // measure the width of each <li> and add it to the total with, increment li counter $('li').each(function() { width_of_text += $(this).width(); number_of_li++; }); // calculate the space between <li>'s so the space is equal var padding = Math.floor((900 - width_of_text)/(number_of_li - 1)); // add the padding the all but the first <li> $('li').each(function(index) { if (index !== 0) { $(this).css("padding-left", padding); } });

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  • How to proxy calls to the instance of an object

    - by mr.b
    Edit: Changed question title from "Does C# allow method overloading, PHP style (__call)?" - figured out it doesn't have much to do with actual question. Also edited question text. What I want to accomplish is to proxy calls to a an instance of an object methods, so I could log calls to any of its methods. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); // need to write log message like "method A called" pc.inner.B(); // need to write log message like "method B called" // ... So, how can I proxy calls to an object instance in extensible way? Method overloading would be most obvious solution (if it was supported in PHP way). By extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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  • Is there a best practice for maintaining history in a database?

    - by Pete
    I don't do database work that often so this is totally unfamiliar territory for me. I have a table with a bunch of records that users can update. However, I now want to keep a history of their changes just in case they want to rollback. Rollback in this case is not the db rollback but more like revert changes two weeks later when they realized that they made a mistake. The distinction being that I can't have a transaction do the job. Is the current practice to use a separate table, or just a flag in the current table? It's a small database, 5 tables each with < 6 columns, < 1000 rows total.

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  • O(log n) algorithm for merging lists and computing rank?

    - by Eternal Learner
    Given two sorted lists, each containing n real numbers, is there a O(log?n) time algorithm to compute the element of rank i (where i coresponds to index in increasing order) in the union of the two lists, assuming the elements of the two lists are distinct? I can think of using a Merge procedure to merge the 2 lists and then find the A[i] element in constant time. But the Merge would take O(n) time. How do we solve it in O(log n) time?

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  • A cross-platform application WPF, ASP.NET, Silverlight, WP7, XAML

    - by J. Lennon
    Considering the fact that all applications will interact with the web project (which will use the cloud or web services).. Is there any way to share my class models between applications? If yes, what is the best way to do it? About sending / receiving data from the Webservice, serialize and deserialize, how can I do this in a simple way without having to manually populate the objects? Any information about this applications would be really helpful!

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  • A better name for INeedSomething... ?

    - by Daniel Severin
    I was trying pick a name for an interface through which I can pass something into an object like: If the object is INeedX then SetX(some x) method will be called; If the object is INeedY then SetY(some y) method will be called; and so on. (funny as hell, I know :) ) I try to find a different name for this kind of interfaces but I can't figure this out. Does anybody have an idea how to name the INeedSomething interface ?

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  • PHP: How do I access child properties from a method in a base object?

    - by Nick
    I'd like for all of my objects to be able to return a JSON string of themselves. So I created a base class for all of my objects to extend, with an AsJSON() method: class BaseObject { public function AsJSON() { $JSON=array(); foreach ($this as $key = $value) { if(is_null($value)) continue; $JSON[$key] = $value; } return json_encode($JSON); } } And then extend my child classes from that: class Package extends BaseObject { ... } So in my code, I expect to do this: $Box = new Package; $Box-SetID('123'); $Box-SetName('12x8x6'); $Box-SetBoxX('12'); $Box-SetBoxY('8'); $Box-SetBoxZ('6'); echo $Box-AsJSON(); But the JSON string it returns only contains the BaseClass's properties, not the child properties. How do I modify my AsJSON() function so that $this refers to the child's properties, not the parent's?

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  • Is this the correct why of speaking to a "Content Manager" Class?

    - by DeanMc
    I am creating a silverlight site. I am currently breaking out my ideas into pieces of functionality. One of the idea's I have is the concept of a content manager. This is essentially a UI control with 4 regions. Top, Bottom, Right & Left. I also have a collection of objects that are considered "Menu Items". These are controls that function as a way to navigate around, similar to links. The idea I have is to implement an IMenuItem interface. Among the standard pieces of information (Text, PageReference, etc) I was also going to hold a reference to the content manager. My idea behind this thinking is that I can pass the PageReference to a property on the ContentManager and then call a method which knows how to update the content manager accordingly. Is this the best way of implementing this or is their some sort of pattern for it?

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  • C#, Generic Lists and Inheritance

    - by Andy
    I have a class called Foo that defines a list of objects of type A: class Foo { List<A> Items = new List<A>(); } I have a class called Bar that can save and load lists of objects of type B: class Bar { void Save(List<B> ComplexItems); List<B> Load(); } B is a child of A. Foo, Bar, A and B are in a library and the user can create children of any of the classes. What I would like to do is something like the following: Foo MyFoo = new Foo(); Bar MyBar = new Bar(); MyFoo.Items = MyBar.Load(); MyBar.Save(MyFoo.Items); Obviously this won't work. Is there a clever way to do this that avoids creating intermediate lists? thanks, Andy

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  • Too many columns to index - use mySQL Partitions?

    - by Christopher Padfield
    We have an application with a table with 20+ columns that are all searchable. Building indexes for all these columns would make write queries very slow; and any really useful index would often have to be across multiple columns increasing the number of indexes needed. However, for 95% of these searches, only a small subset of those rows need to be searched upon, and quite a small number - say 50,000 rows. So, we have considered using mySQL Partition tables - having a column that is basically isActive which is what we divide the two partitions by. Most search queries would be run with isActive=1. Most queries would then be run against the small 50,000 row partition and be quick without other indexes. Only issue is the rows where isActive=1 is not fixed; i.e. it's not based on the date of the row or anything fixed like that; we will need to update isActive based on use of the data in that row. As I understand it that is no problem though; the data would just be moved from one partition to another during the UPDATE query. We do have a PK on id for the row though; and I am not sure if this is a problem; the manual seemed to suggest the partition had to be based on any primary keys. This would be a huge problem for us because the primary key ID has no basis on whether the row isActive.

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  • Explaining your system to a client

    - by Sir Graystar
    I'm currently developing a small Database Management System for a local company. How would you go about explaining how the system you have designed to a client? If they are non-technical and have no understanding of programming, how would you go about showing what the system will do and how it will do it? I guess some sort of visual representation of the system but this seems very patronising to me.

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