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Should I re-use UI elements across view controllers?

- by Endemic

In the iPhone app I'm currently working on, I'd like two navigation controllers (I'll call them A and B) to have toolbars that are identical in appearance and function. The toolbar in question will look like this: [(button) (flexible-space) (label)] For posterity's sake, the label is actually a UIBarButtonItem with a custom view. My design requires that A always appear directly before B on the navigation stack, so B will never be loaded without A having been loaded. Given this layout, I started wondering, "Is it worth it to re-use A's toolbar items in B's toolbar?" As I see it, my options are: 1. Don't worry about re-use, create the toolbar items twice 2. Create the toolbar items in A and pass them to B in a custom initializer 3. Use some more obscure method that I haven't thought of to hold the toolbar constant when pushing a view controller As far as I can see, option 1 may violate DRY, but guarantees that there won't be any confusion on the off chance that (for example) the button may be required to perform two different (no matter how similar) functions for either view controller in future versions of the app. Were that to happen, options 2 or 3 would require the target-action of the button to change when B is loaded and unloaded. Even if the button were never required to perform different functions, I'm not sure what its proper target would be under option 2. All in all, it's not a huge problem, even if I have to go with option 1. I'm probably overthinking this anyway, trying to apply the dependency injection pattern where it's not appropriate. I just want to know the best practice should this situation arise in a more extreme form, like if a long chain of view controllers need to use identical (in appearance and function) UI elements.

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Joomla get plugin id

- by Christian Sciberras

I wrote a Joomla plugin which will eventually load a library. The path to library is a plugin parameter, as such when the path is incorrect, a message pops up in the backend, together with a link to edit the plugin parameters: /administrator/index.php?option=com_plugins&view=plugin&client=site&task=edit&cid[]=36 See the 36 at the end? That's my plugin's id in the database (table jos_plugins). My issue is that this id changes on installation, ie, on different installs, it would be something else. So I need to find this id programmatically. The problem is that I couldn't find this id from the plugin object itself (as to why not, that would be joomla's arguably short-sighted design decision). So unless you know about some neat trick, (I've checked and double checked JPlugin and JPluginHelper classes), I'll be using the DB. Edit; Some useful links: http://docs.joomla.org/Plugin_Developer_Overview http://api.joomla.org/Joomla-Framework/Plugin/JPlugin.html http://api.joomla.org/Joomla-Framework/Plugin/JPluginHelper.html http://forum.joomla.org/viewtopic.php?p=2227737 Guess I'll be using the wisdom from that last link...

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Defining implicit and explicit casts for C# interfaces

- by ehdv

Is there a way to write interface-based code (i.e. using interfaces rather than classes as the types accepted and passed around) in C# without giving up the use of things like implicit casts? Here's some sample code - there's been a lot removed, but these are the relevant portions. public class Game { public class VariantInfo { public string Language { get; set; } public string Variant { get; set; } } } And in ScrDictionary.cs, we have... public class ScrDictionary: IScrDictionary { public string Language { get; set; } public string Variant { get; set; } public static implicit operator Game.VariantInfo(ScrDictionary s) { return new Game.VariantInfo{Language=sd.Language, Variant=sd.Variant}; } } And the interface... public interface IScrDictionary { string Language { get; set; } string Variant { get; set; } } I want to be able to use IScrDictionary instead of ScrDictionary, but still be able to implicitly convert a ScrDictionary to a Game.VariantInfo. Also, while there may be an easy way to make this work by giving IScrDictionary a property of type Game.VariantInfo my question is more generally: Is there a way to define casts or operator overloading on interfaces? (If not, what is the proper C# way to maintain this functionality without giving up interface-oriented design?)

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C++ const-reference semantics?

- by Kristoffer

Consider the sample application below. It demonstrates what I would call a flawed class design. #include <iostream> using namespace std; struct B { B() : m_value(1) {} long m_value; }; struct A { const B& GetB() const { return m_B; } void Foo(const B &b) { // assert(this != &b); m_B.m_value += b.m_value; m_B.m_value += b.m_value; } protected: B m_B; }; int main(int argc, char* argv[]) { A a; cout << "Original value: " << a.GetB().m_value << endl; cout << "Expected value: 3" << endl; a.Foo(a.GetB()); cout << "Actual value: " << a.GetB().m_value << endl; return 0; } Output: Original value: 1 Expected value: 3 Actual value: 4 Obviously, the programmer is fooled by the constness of b. By mistake b points to this, which yields the undesired behavior. My question: What const-rules should you follow when designing getters/setters? My suggestion: Never return a reference to a member variable if it can be set by reference through a member function. Hence, either return by value or pass parameters by value. (Modern compilers will optimize away the extra copy anyway.)

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Comparing lists of field-hashes with equivalent AR-objects.

- by Tim Snowhite

I have a list of hashes, as such: incoming_links = [ {:title => 'blah1', :url => "http://blah.com/post/1"}, {:title => 'blah2', :url => "http://blah.com/post/2"}, {:title => 'blah3', :url => "http://blah.com/post/3"}] And an ActiveRecord model which has fields in the database with some matching rows, say: Link.all => [<Link#2 @title='blah2' @url='...post/2'>, <Link#3 @title='blah3' @url='...post/3'>, <Link#4 @title='blah4' @url='...post/4'>] I'd like to do set operations on Link.all with incoming_links so that I can figure out that <Link#4 ...> is not in the set of incoming_links, and {:title => 'blah1', :url =>'http://blah.com/post/1'} is not in the Link.all set, like so: #pseudocode #incoming_links = as above links = Link.all expired_links = links - incoming_links missing_links = incoming_links - links expired_links.destroy missing_links.each{|link| Link.create(link)} One route I've tried: I'd rather not rewrite Array#- and such, and I'm okay with converting incoming_links to a set of unsaved Link objects; so I've tried overwriting hash eql? and so on in Link so that it ignored the id equality that AR::Base provides by default. But this is the only place this sort of equality should be considered in the application - in other places the Link#id default identity is required. Is there some way I could subclass Link and apply the hash, eql?, etc overwriting there? The other route I've tried is to pull out the attributes hash for each Link and doing a .slice('id',...etc) to prune the hashes down. But this requires writing seperate methods for keeping track of the Link objects while doing set operations on the hashes, or writing seperate Collection classes to wrap the incoming_links hash-list and Link-list which seems a bit overkill. What is the best way to design this interaction? Extra credit for cleanliness.

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two view controllers and reusability with delegate

- by netcharmer

Newbie question about design patterns in objC. I'm writing a functionality for my iphone app which I plan to use in other apps too. The functionality is written over two classes - Viewcontroller1 and Viewcontroller2. Viewcontroller1 is the root view of a navigation controller and it can push Viewcontroller2. Rest of the app will use only ViewController1 and will never access Viewcontroller2 directly. However, triggered by user events, Viewcontroller2 has to send a message to the rest of the app. My question is what is the best way of achieving it? Currently, I use two level of delegation to send the message out from Viewcontroller2. First send it to Viewcontroller1 and then let Viewcontroller1 send it to rest of the app or the application delegate. So my code looks like - //Viewcontroller1.h @protocol bellDelegate -(int)bellRang:(int)size; @end @interface Viewcontroller1 : UITableViewController <dummydelegate> { id <bellDelegate> delegate; @end //Viewcontroller1.m @implementation Viewcontroller1 -(void)viewDidLoad { //some stuff here Viewcontroller2 *vc2 = [[Viewcontroller2 alloc] init]; vc2.delegate = self; [self.navigationController pushViewController:vc2 animated:YES]; } -(int)dummyBell:(int)size { return([self.delegate bellRang:size]); } //Viewcontroller2.h @protocol dummyDelegate -(int)dummyBell:(int)size; @end @interface Viewcontroller2 : UITableViewController { id <dummyDelegate> delegate; @end //Viewcontroller2.m @implementation Viewcontroller2 -(int)eventFoo:(int)size { rval = [self.delegate dummyBell:size]; } @end

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specified size of td

- by ognjenb

<table class="data-table"> <tr> <th style="width: 200px;"> Description </th> </tr> <% foreach (var item in Model) { %> <tr> <td style="width: 200px;"> <%= Html.Encode(item.Description) %> </td> </tr> </table> browser html: <table class="data-table"> <tr> <th style="width: 200px;"> Description </th> </tr> <tr> <td > This is description </td> </tr> </table> Why this td size is not to apply on View page? In Design view on VS 2008 td size is applied, but after run project in my browser not have specified size

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RESTful API: How to model JSON representation?

- by Jan P.

I am designing a RESTful API for a booking application. You can request a list of accommodations. And that's where I don't really know how to design the JSON represenation. This is my XML representation: <?xml version="1.0" encoding="utf-8"?> <accommodations> <accommodation> <name>...</name> <category>couch</category> </accommodation> <accommodation> <name>...</name> <category>room</category> </accommodation> <accommodations> My first try to convert this to JSON resulted in this output (1): { "0": { "name": "...", "category": "couch" }, "1": { "name": "...", "category": "room" } } But as I looked how others APIs did it, I found something looking more like this (2): [ { "name": "...", "category": "couch" }, { "name": "...", "category": "room" } ] I know version 1 is an object, and version 2 an array. But which one is better in this case?

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Calling member functions dynamically

- by user652511

I'm pretty sure it's possible to call a class and its member function dynamically in Delphi, but I can't quite seem to make it work. What am I missing? // Here's a list of classes (some code removed for clarity) moClassList : TList; moClassList.Add( TClassA ); moClassList.Add( TClassB ); // Here is where I want to call an object's member function if the // object's class is in the list: for i := 0 to moClassList.Count - 1 do if oObject is TClass(moClassList[i]) then with oObject as TClass(moClassList[i]) do Foo(); I get an undeclared identifier for Foo() at compile. Clarification/Additional Information: What I'm trying to accomplish is to create a Change Notification system between business classes. Class A registers to be notified of changes in Class B, and the system stores a mapping of Class A - Class B. Then, when a Class B object changes, the system will call a A.Foo() to process the change. I'd like the notification system to not require any hard-coded classes if possible. There will always be a Foo() for any class that registers for notification. Maybe this can't be done or there's a completely different and better approach to my problem. By the way, this is not exactly an "Observer" design pattern because it's not dealing with objects in memory. Managing changes between related persistent data seems like a standard problem to be solved, but I've not found very much discussion about it. Again, any assistance would be greatly appreciated. Jeff

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Objective C - creating concrete class instances from base class depending upon type

- by indiantroy

Just to give a real world example, say the base class is Vehicle and concrete classes are TwoWheeler and FourWheeler. Now the type of the vehicle - TwoWheeler or FourWheeler, is decided by the base class Vehicle. When I create an instance of TwoWheeler/FourWheeler using alloc-init method, it calls the super implementation like below to set the value of common properties defined in the Vehicle class and out of these properties one of them is type that actually decides if the type is TwoWheeler or FourWheeler. if (self = [super initWithDictionary:dict]){ [self setOtherAttributes:dict]; return self; } Now when I get a collection of vehicles some of them could be TwoWheeler and others will be FourWheeler. Hence I cannot directly create an instance of TwoWheeler or FourWheeler like this Vehicle *v = [[TwoWheeler alloc] initWithDictionary:dict]; Is there any way I can create an instance of base class and once I know the type, create an instance of child class depending upon type and return it. With the current implementation, it would result in infinite loop because I call super implementation from concrete class. What would be the perfect design to handle this scenario when I don't know which concrete class should be instantiated beforehand?

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Python OOP - object has no attribute

- by user1744269

I am attempting to learn how to program. I really do want to learn how to program; I love the building and design aspect of it. However, in Java and Python, I have tried and failed with programs as they pertain to objects, classes, methods.. I am trying to develop some code for a program, but im stumped. I know this is a simple error. However I am lost! I am hoping someone can guide me to a working program, but also help me learn (criticism is not only expected, but APPRECIATED). class Converter: def cTOf(self, numFrom): numFrom = self.numFrom numTo = (self.numFrom * (9/5)) + 32 print (str(numTo) + ' degrees Farenheit') return numTo def fTOc(self, numFrom): numFrom = self.numFrom numTo = ((numFrom - 32) * (5/9)) return numTo convert = Converter() numFrom = (float(input('Enter a number to convert.. '))) unitFrom = input('What unit would you like to convert from.. ') unitTo = input('What unit would you like to convert to.. ') if unitFrom == ('celcius'): convert.cTOf(numFrom) print(numTo) input('Please hit enter..') if unitFrom == ('farenheit'): convert.fTOc(numFrom) print(numTo) input('Please hit enter..')

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Guidelines for creating a programming-language enjoyable to write programs in?

- by sub

I'm currently working on the topic of programming-languages and interpreter-design. I have already created several programming languages but couldn't reach my goal so far: Create a programming-language which focuses on giving the programmer a good feeling when writing code in it. It should just be fun and/or interesting and in no case annoying to write something in it. I get this feeling when writing code in Python. I sometimes get the opposite with PHP and in rare cases when having to reinvent some wheel in C++. So I've tried to figure out some syntactical features to make programming in my new language fun, but I just can't find any. Which concrete features, maybe mainly in terms of syntax, do/could make programming in a language fun? Examples: I find it enjoyable to program in Ruby because of it's use of code blocks. It would be nice if you could include exactly one example in your answer Those features do not have to already exist in any language! I'm doing this because I have experienced extreme rises in (my own) productivity when programming in languages I love (because of particular features).

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Update MySQl table onDrop?

- by dougvt

Hi all. I am writing a PHP/MySQL application (using CodeIgniter) that uses some jQuery functionality for dragging table rows. I have a table in which the user can drag rows to the desired order (kind of a queue for which I need to preserve the rank of each row). I've been trying to figure out how to (and whether I should) update the database each time the user drops a row, in order to simplify the UI and avoid a "Save" button. I have the jQuery working and can send a serialized list back to the server onDrop, but is it good design practice to run an update query this often? The table will usually have 30-40 rows max, but if the user drags row 1 far down the list, then potentially all the rows would need to be updated to update the rank field. I've been wondering whether to send a giant query to the server, to loop through the rows in PHP and update each row with its own Update query, to send a small serialized list to a stored procedure to let the server do all the work, or perhaps a better method I haven't considered. I've read that stored procedures in MySQL are not very efficient and use a separate process for each call. Any advice as to the right solution here? Thanks very much for your help!

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Get height of DIV and it's content with JQuery

- by user1012403

I have a div which contains several elements: <div class="menuItem designMenu" id="dMenu"> <ul class="menuList menu"> <li class="menuHeader">Design</li> <li class="projectHeader">Mother</li> <li class="projectBody">Some text here</li> <li class="more">More</li> </ul> </div> I need to get the height of the dMenu items that I can animate it upwards, including all the content inside. My Javascript currently: var designHeight = $("#dMenu").height(); Returns nothing. I've tried offsetHeight, scrollHeight, and everything else Google turns up. I'm running the JQuery at the end of the body, inside a document ready function. The reason to get the height to animate, instead of doing it manually, is that a: I'd like to learn how and b: I don't yet know how many items will be int he div. Thanks.

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Alert Box Methods

- by Vecta

I just need a little advice on what may be the best method for handling my situation. I'm in need of placing three buttons in the sidebar of the website I maintain. The website is massive and hard to handle. Currently, it's all HTML files (there are over 10,000 of them believe it or not). We're transitioning to a database website so I don't want to make any sweeping changes that are site-wide, as they may just be scrapped in our re-design process in coming months. However, these buttons are for an application process. When you click on them, an alert box will need to pop up to give you a bit of information and they either allow you to cancel the action or proceed. The buttons are currently located in the left nav which is included on every page of the website. Would it be possible to accomplish this using JS or jQuery? I'd be unable to easily add scripts into the tags on all of the applicable pages, but I'd like to avoid the browser driven "http://www...Says: blah blah" message if possible. Any insight is greatly appreciated! Thank you!

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Best strategies for reading J code

- by estanford

I've been using J for a few months now, and I find that reading unfamiliar code (e.g. that I didn't write myself) is one of the most challenging aspects of the language, particularly when it's in tacit. After a while, I came up with this strategy: 1) Copy the code segment into a word document 2) Take each operator from (1) and place it on a separate line, so that it reads vertically 3) Replace each operator with its verbal description in the Vocabulary page 4) Do a rough translation from J syntax into English grammar 5) Use the translation to identify conceptually related components and separate them with line breaks 6) Write a description of what each component from (5) is supposed to do, in plain English prose 7) Write a description of what the whole program is supposed to do, based on (6) 8) Write an explanation of why the code from (1) can be said to represent the design concept from (7). Although I learn a lot from this process, I find it to be rather arduous and time-consuming -- especially if someone designed their program using a concept I never encountered before. So I wonder: do other people in the J community have favorite ways to figure out obscure code? If so, what are the advantages and disadvantages of these methods?

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Write a completely fluid HTML page (using '%' instead of 'px' for EVERY element height/width)

- by barak manos

I am designing my HTML pages to be completely fluid: For every element in the mark-up (HTML), I am using 'style="height:%;width:%"' (instead of 'style="height:*px;width:*px"'). This approach seems to work pretty well, except for when changing the window measurements, in which case, the web page elements change their position and end up "on top of each other". I have come up with a pretty good run-time (java-script) solution to that: var elements = document.getElementsByTagName("*"); for (var i=0; i < elements.length; i++) { if (elements[i].style.height) elements[i].style.height = elements[i].offsetHeight+"px"; if (elements[i].style.width ) elements[i].style.width = elements[i].offsetWidth +"px"; } The only problem remaining is, that if the user opens up the website by entering the URL into a non-maximized window, then the page fits that portion of the window. Then, when maximizing the window, the page remains in its previous measurements. So in essence, I have solved the initial problem (when changing the window measurements), but only when the window is initially in its maximum size. Any ideas on how to tackle this problem? (given that I would like to keep my "% page-design" as is).

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Is there any trick to match two XML by one XSLT?

- by brain_pusher

Is there any trick to match two XML by one XSLT? I mean the way I can apply XSLT to a parameter passed. For example (I missed declarations to be short). XML1: XML to be transformed: <myData> <Collection> </Collection> </myData> XSLT need to be applied to the previous XML: <xsl:param name='items' /> <xsl:template match='Collection'>  </xsl:template> XML2: XML data passed as the parameter 'items': <newData> <Item>1</Item> <Item>2</Item> <Item>3</Item> </newData> And I need to create a set of nodes in the 'Collection' node in XML1 for each 'Item' element in XML2 using XSLT. And I do not know what XML2 contains exactly at design time. It is generated at runtime, so I can't place it inside XSLT, I know only its schema.

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jQuery removeClass(), how it works

- by centro

I have images on my page. User can add more images onto the page by clicking a button. New images are added asynchronously. Initially, each image on page use a special class to be used when the image is loaded. After the image is loaded, that class is removed. Each image being loaded has the class imageLoading: <img class="imageLoading" scr="someimage.png"> After those images are loaded, I remove that class (simplified code without details): $('img.imageLoading') .each(function(){ $(this) .load(function(){ $(this) .removeClass('imageloading'); });}); Visually, I see that style is removed. But when I run the query again: $('img.imageLoading') I see via debugging that all images, not just loading ones, are returned, i.e. it works like I didn't remove the class for the images that were already loaded. I had a look into the page source, and I saw that actually in HTML the class was not removed, though removeClass() was called. Is that behavior by design that all visual changes are applied but the class attribute is not removed in HTML code? If so, how it can be workarounded in this case. Or, probably, I missed something.

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A loop (while/foreach) with "offset" wrapping and

- by DarkGhostHunter

After applying what wrapping objects using math operator, I just tought it will be over. But no. By far. <?php $faces= array( 1 => '<div class="block">happy</div>', 2 => '<div class="block">sad</div>', (sic) 21 => '<div class="block">angry</div>' ); $i = 1; foreach ($faces as $face) { echo $face; if ($i == 3) echo '<div class="block">This is and ad</div>'; if ($i % 3 == 0) { echo "<br />"; // or some other wrapping thing } $i++; } ?> In the code I have to put and ad after the second one, becoming by that the third object. And then wrap the three all in a <div class="row"> (a br after won't work out by design reasons). I thought I will going back to applying a switch, but if somebody put more elements in the array that the switch can properly wrap, the last two remaining elements are wrapped openly. Can i add the "ad" to the array in the third position? That would make things simplier, only leaving me with guessing how to wrap the first and the third, the fourth and the sixth, an so on.

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include ::before pseudo class in javascript

- by user1955837

Why is this thing not working? If I remove ::before from javascript and css it works. But due to the design needs there has to be a ::before. How do I point to the class + ::before? $(function () { var sections = $("section"); var navigation_links = $("nav a"); sections.waypoint({ handler: function (event, direction) { var active_section; active_section = $(this); if (direction === "up") active_section = active_section.prev(); var active_link = $('nav a[href="#' + active_section.attr("id") + '"]'); navigation_links.removeClass("selected::before"); active_link.addClass("selected::before"); }, offset: '25%' }) }); css: .selected::before { display: block; content: ""; margin-top: 6px; width: 8px; height: 8px; background: url(../img/sprite.png) -126px -196px; background-size: 400px 480px; float: left; margin-left: 20px; margin-right: 20px; }

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How to process more that one XML document in XSLT?

- by brain_pusher

Is there any trick to match two XML by one XSLT? I mean the way I can apply XSLT to a parameter passed. For example (I missed declarations to be short). XML1: XML to be transformed: <myData> <Collection> </Collection> </myData> XSLT need to be applied to the previous XML: <xsl:param name='items' /> <xsl:template match='Collection'>  </xsl:template> XML2: XML data passed as the parameter 'items': <newData> <Item>1</Item> <Item>2</Item> <Item>3</Item> </newData> And I need to create a set of nodes in the 'Collection' node in XML1 for each 'Item' element in XML2 using XSLT. And I do not know what XML2 contains exactly at design time. It is generated at runtime, so I can't place it inside XSLT, I know only its schema.

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Main purpose of this task is to calculate volumes and surface areas of three dimensional geometric shapes like, cylinders, cones.

- by Csc_Girl_Geek

In Java Language Design your classes as below introducing: an Interface named “GeometricShapes” an abstract class named “ThreeDShapes” two child classes of ThreeDShapes: Cylinders and Cones. One test class names “TestShapes” Get the output for volumes and surface areas of cylinders and cones along with respective values of their appropriate input variables. Try to use toString() method and array. Your classes should be designed with methods that are required for Object-Oriented programming. So Far I Have: package Assignment2; public interface GeometricShapes { public void render(); public int[] getPosition(); public void setPosition(int x, int y); } package Assignment2; public abstract class ThreeDShapes implements GeometricShapes { public int[] position; public int[] size; public ThreeDShapes() { } public int[] getPosition() { return position; } public void setPosition(int x, int y) { position[0] = x; position[1] = y; } } package Assignment2; public class Cylinders extends ThreeDShapes { public Cylinder() { } public void render() { } } I don't think this is right and I do not know how to fix it. :( Please help.

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Storing data in XML or MongoDB

- by user766473

Here is my usecase. 1.Have some data, which I am storing now in the xml files. The data that I am storing is not persistent i.e I would be deleting the user data once the user logs out. 2.My server communicates with the client using the XML requests and responses. So initially we decided, since we are sending the XML as response, lets store it in XML so that conversion from database to XML format time is saved. 3.Client will request for XML based on some filter conditions. So will have to use XQUERY. 4.Maximum of 100 entries will be there in an XML, atleast as of now. Now I would like to hear some advice on whether I should use XML or mongodb. My Concerns : 1. How good is it to store temporary data in mongodb and delete/take backup once done with session 2. Conversion from mongodb json format to XML. 3. Handling the changes in the schema design. Cant use any other DB than mongodb. As some persistent operation or still done on mongodb. Thanks in advance.

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SQL Server: Why use shorter VARCHAR(n) fields?

- by chryss

It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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