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  • How does one bind to a List<DataRow> collection in WPF XAML?

    - by Elan
    Using a DataTable or DataView, one can specify the binding in XAML for example as follows: <Image Source="{Binding Thumbnail}" /> In my case I have created a List collection of DataRow objects and the above is not working. This is my data source: List<DataRow> I could of course convert the List< to a DataTable, but I am curious if there was a way to specify the binding in XAML to access the "Thumbnail" column within the DataRow that is stored in a List< collection. Elan

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  • php not showing all images

    - by jera
    I a writing a gallery app in php. The images are dynamically displayed through php. On each load of the page, not all images are showing. it does this randomly, on each load. I have not had this problem before, as I am new to php. My previous apps where all in perl, and I had no dynamic image display problems when using that language. check it here: http://dev.system-engine.com/dev/exec/pcli.php?R=%27/Paintings%27&cfg=%22fgal%22 all help appreciated. thank, Jer A

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  • trying to fade out a top div on hover to reveal working links in text below using JQuery

    - by Heath
    I need to fade a div (and image) to reveal a div underneath (text with clickable links) using jQuery. <script> $(document).ready(function(){ $("img.a").hover( function() { $(this).stop().animate({"opacity": "0"}, "slow"); }, function() { $(this).stop().animate({"opacity": "1"}, "slow"); }); }); </script> Used the above code and all worked well, until I went to click the links. Seems the top hidden div is preventing me from doing so. Tried the replaceWith function and that allowed me to click the links too - but couldn't get it to go back to showing original div when I moused out. Also, bossman wants the transition to be gradual - like a fade... Any suggestions? Many thanks! Heath

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  • Examples of networked Flash games

    - by videodnd
    Maybe I am asking the wrong questions, because I don't see any sample projects out there. I know Flash developers have done Kiosks and renovated arcade games. "Come on, we see Flash everywhere." Is there a sample project I could be pointed towards, it would be an ass-saver. Can I prepare my swf files like an image gallery and receive XML commands to load it? Where do I start? Flash/After Effects skills have got me through so far, but I need help!!! It would be fun if it wasn't so stressful. Criteria TCP/IP socket connection Flash package XML commands load swf file in to a container Additional Questions How do I prepare my Flash files and XML sheet to receive commands "any sample out there"? What about e.data, urlLoad, xmlSocket Class, XMLCP/IP XML socket connection to load Is binary or XML method better for loading and reloading swf files? Do I need Red5 or a media server? videoDnd, Ambitious Development Noob

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  • Graphics/Vision Interesting Topics

    - by Myx
    Hello: I would like to do an interesting project for a computer graphics course. I know that there is a lot of literature out there (i.e. SIGGRAPH conference papers). I have a very large range of interest with regard to computer graphics (i.e. image processing, 3D modeling, rendering, animation). However, I've only taken computer vision/graphics for 2 semesters and thus don't have too much background experience, except for the class projects that I had to do. I've been looking through SIGGRAPH papers trying to see if there is anything that will be of interest to me but the literature is extremely vast. I was wondering if anyone has any topic suggestions, anything interesting that you ran across that you could recommend. I would prefer to do something fun yet slightly challenging (not really interested in making a shooter game). If this question does not belong here, I apologize and please let me know where I should move it. Thanks!

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  • How to change *.ico for button in running mode?

    - by karikari
    I am currently doing visual c++ for an Internet Explorer toolbar button. I have a registration script file (*.rgs) that defines or maybe register the features of my button inside the Windows registry. My objective is, I want my button to change its *.ico image, based on certain conditions process from my *.cpp file. My problem is, I don't understand, how can I somehow change the *.ico file for my button in real time, during my application is running? For example, IF f = 1, ico_file = green.ico; ELSE ico_file = red.ico; Any idea, that you guys can point to me, how can I change the *.ico file for my Internet Explorer toolbar button while the IE is running.

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  • Bitmapfontatlas cocos2d performance issue

    - by meboz
    This question was also asked in the cocos2d forums but they are a little slower than here. Hi, Im trying to resolve a performance issue in my game. I have all of my game images on the one spritesheet. I now have a score label for which i have generated a font file with the Hiero tool. Ideally I'd like to update my score label with the current score on every update. However there seems to be a significant performance hit when doing so, which i believe is the result of the game images texture and the font texture swapping each update. Can anyone suggest a way to avoid this? Possibly by combining the font images with the game images in the one image file to avoid the texture swapping? Cheers

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  • What is the maximum distance from an anchor point to a bezier curve?

    - by drawnonward
    Given a cubic bezier curve P0,P1,P2,P3 with the following properties: • Both P1 and P2 are on the same side of the line formed by P0 and P3. • P2 can be projected onto the line segment formed by P0 and P3 but P1 cannot. What is the T value for the point on the curve farthest from P3? Here is an image with an example curve. The curve bulges on the left, so there is a point on the curve farther from P3 than P0. I found this reference for finding the minimum distance from an arbitrary point to a curve. Is trial and error the only way to solve for maximum distance as well? Does it make any difference that the point is an anchor on the curve? Thanks

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  • design time usercontrols - I can't see anything!

    - by taglius
    newbie question, please forgive... I'm developing a Wpf UserControl that will eventually be bound to a business object. The usercontrol is little more than a series of laid out TextBlocks, and perhaps (later) an image or two. As I'm laying out the usercontrol, I can put dummy text into all the TextBlocks so I can see what the usercontrol will look like, but as soon as I change the text property to contain the Binding information: <TextBlock Margin="0,12.8,42,0" Name="lblLastName" FontSize="8" Height="19" VerticalAlignment="Top" Text="{Binding Mode=OneWay, Path=LastName}"/> Then I can no longer see the textbox, or any "placeholder" text. This makes it very difficult to adjust the location and sizes of all the controls on the UserControl. In WinFormas programming, you could set binding information independently of the Text property, so you could at least see the Placeholder text during design time development. It's going to be pretty hard to visually arrange a bunch of invisible TextBlocks! What's the standard solution for this?

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  • Is MacBook powerful enough to do Ipad development? or do I need a MacBook Pro?

    - by ronaldwidha
    The title probably says it all. Considering an ipad's processor is nothing compared to a macbook, I would think a Macbook should be more than capable to run the simulator. However, not knowing much about iphone/ipad development, I'd like to get some opinions on this. for e.g. how many apps are typically need to be run for ipad dev (editor, debugger, perf monitor, trace log, etc). are these apps resource (memory, cpu) intensive? please do not take into consideration the actual image, 3d, video, sound development. I understand one would need quite a beefy machine to produce these type of creative assets. What I'm looking at is a machine to do code development, physics, putting together the produced assets (images, vector graphics, 3d video, sound, etc).

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  • click li, go to next li

    - by steve
    Can't find a simple solution to this, I know it's easy and I've tried a few things but I can't quite get it to work. I'm currently working with a sidescrolling site and I want every time you click an image (contained in an li) it scrolls to the next li. I have jQuery plugin localscroll so it smoothly goes from one to the next, and that's working. I need to now write a code that triggers jQuery to utilize the localscroll function and go to the next li. Right now I have this, but I know it's not right: $(document).ready(function () { var gallery = $('.wrapper ul li') $(gallery).click(function() { $.localscroll().next(li); }); });

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  • [wxWidgets] How to store wxImage into database, using C++?

    - by Thomas Matthews
    I have some wxImages and I would like to store them into a BLOB (Binary Large OBject) field in a MySQL database. There are no methods in wxImage nor wxBitmap for obtaining the binary data as an array of unsigned char so I can load into the database. My current workaround is to write the image to a temporary file, then load the BLOB field directly from the file. Is there a more efficient method to load and store a wxImage object into a MySQL BLOB field? I am using MySql C++ connector 1.05, MS Visual Studio 2008, wxWidgets and C++.

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  • which is the best for build a Gantt-chart like application Flex or Flash Action Script?

    - by coderex
    Which is the best for build an application show like in image. For the better graphics and performance wise. I want to know Flash for Flex is more suitable for this. In Flash ca we be able to build a grid kind of applications easily? I headed that Flex have the functions to handle grid and other things. Drag & scroll Zoom like feature. but am not sure able the graphics of flex. Is the components are customizable.. Please help me.

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  • Doctrine_Table_Exception: Unknown relation alias [closed]

    - by Sadiqur Rahman
    I am getting following error message: Doctrine_Table_Exception: Unknown relation alias shoesTable in /home/public_html/projects/giftshoes/system/database/doctrine/Doctrine/Relation/Parser.php on line 237 My Code is below: ------------BaseShoe------------ <?php // Connection Component Binding Doctrine_Manager::getInstance()->bindComponent('Shoes', 'sadiqsof_giftshoes'); /** * BaseShoes * * This class has been auto-generated by the Doctrine ORM Framework * * @property integer $sku * @property string $name * @property string $keywords * @property string $description * @property string $manufacturer * @property float $sale_price * @property float $price * @property string $url * @property string $image * @property string $category * @property Doctrine_Collection $Viewes * * @package ##PACKAGE## * @subpackage ##SUBPACKAGE## * @author ##NAME## <##EMAIL##> * @version SVN: $Id: Builder.php 6820 2009-11-30 17:27:49Z jwage $ */ abstract class BaseShoes extends Doctrine_Record { public function setTableDefinition() { $this->setTableName('shoes'); $this->hasColumn('sku', 'integer', 4, array( 'type' => 'integer', 'fixed' => 0, 'unsigned' => false, 'primary' => true, 'autoincrement' => false, 'length' => '4', )); $this->hasColumn('name', 'string', 255, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '255', )); $this->hasColumn('keywords', 'string', 255, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '255', )); $this->hasColumn('description', 'string', null, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '', )); $this->hasColumn('manufacturer', 'string', 20, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '20', )); $this->hasColumn('sale_price', 'float', null, array( 'type' => 'float', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '', )); $this->hasColumn('price', 'float', null, array( 'type' => 'float', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '', )); $this->hasColumn('url', 'string', null, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '', )); $this->hasColumn('image', 'string', null, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '', )); $this->hasColumn('category', 'string', 50, array( 'type' => 'string', 'fixed' => 0, 'unsigned' => false, 'primary' => false, 'notnull' => true, 'autoincrement' => false, 'length' => '50', )); } public function setUp() { parent::setUp(); $this->hasMany('Viewes', array( 'local' => 'sku', 'foreign' => 'sku')); } } --------------ShoesTable-------- <?php class ShoesTable extends Doctrine_Table { function getAllShoes($from = 0, $total = 15) { $q = Doctrine_Query::create() ->from('Shoes') ->limit($total) ->offset($from); return $q->execute(array(), Doctrine::HYDRATE_ARRAY); } } ---------------Shoes Model----------------- <?php /** * Shoes * * This class has been auto-generated by the Doctrine ORM Framework * * @package ##PACKAGE## * @subpackage ##SUBPACKAGE## * @author ##NAME## <##EMAIL##> * @version SVN: $Id: Builder.php 6820 2009-11-30 17:27:49Z jwage $ */ class Shoes extends BaseShoes { function __construct() { parent::__construct(); $this->shoesTable = Doctrine::getTable('Shoes'); } function getAllShoes() { return $this->shoesTable->getAllShoes(); } }

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  • Python Threading

    - by anteater7171
    I'm trying to make a simple program that continually displays and updates a label that displays the CPU usage, while having other unrelated things going on. I've done enough research to know that threading is likely going to be involved. However, I'm having trouble applying what I've seen in simple examples of threading to what I'm trying to do. What I currently have going: import Tkinter import psutil,time from PIL import Image, ImageTk class simpleapp_tk(Tkinter.Tk): def __init__(self,parent): Tkinter.Tk.__init__(self,parent) self.parent = parent self.initialize() def initialize(self): self.labelVariable = Tkinter.StringVar() self.label = Tkinter.Label(self,textvariable=self.labelVariable) self.label.pack() self.button = Tkinter.Button(self,text='button',command=self.A) self.button.pack() def A (self): G = str(round(psutil.cpu_percent(), 1)) + '%' print G self.labelVariable.set(G) def B (self): print "hello" if __name__ == "__main__": app = simpleapp_tk(None) app.mainloop() In the above code I'm basically trying to get command A continually running, while allowing command B to be done when the users presses the button.

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  • iphone problem adding splashscreen

    - by zebra
    hi all, i've a little problem, i've add a default.png in my app and it work. I've modify my file, delete file and reference and upload my new file. On my iphone the image does not appear, only some second of blackscreen and after my app start. In the simulator the splashscreen appear. I've try to delete my app on iphone, make a clean all and rebuild & install but nothing... I've try to make clean all, close xcode, delete default.png to my project directory (sometimes exist, sometimes no), open xcode, add my file and build & install on my iphone but nothing... Any ideas?

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  • How to build march-0 for different architectures?

    - by Victor Lin
    I have some dylibs to load from python with ctypes. I can load libbass.dylib without problem, but I can't load the self-compiled libmp3lame.dylib. Here is the error I get. OSError: dlopen(libmp3lame.dylib, 6): no suitable image found. Did find: libmp3lame.dylib: mach-o, but wrong architecture Then, I inspect the file type of those libs. Here is the result of libbass.dylib: libbass.dylib: Mach-O universal binary with 2 architectures libbass.dylib (for architecture i386): Mach-O dynamically linked shared library i386 libbass.dylib (for architecture ppc): Mach-O dynamically linked shared library ppc And here is the self-compiled one: libmp3lame.dylib: Mach-O 64-bit dynamically linked shared library x86_64 I did compile the lame library with the install instructions: ./configure make make install I'm new to mac system, here comes the problem: how to build the libmp3lame.dylib so that it supports different architecture I want? Thanks.

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  • ApiChange Is Released!

    - by Alois Kraus
    I have been working on little tool to simplify my life and perhaps yours as developer as well. It is basically a command line tool that allows you to execute queries on your compiled .NET code base. The main purpose is to find out how big the impact of an api change would be if you changed this or that.  Now you can do high level operations like Diff public types for breaking changes. Who uses a method? Who uses a type? Who uses implements an interface? Who references me? What format has the binary  (32/64, Managed C++, Pure IL, Unmanaged)? Search for all event subscribers and unsubscribers. A unique feature is to check for event subscription imbalances. Forgotten event subscriptions are the 90% cause of managed memory leaks. It is done at a per class level. If one class does subscribe to one event more often than it does unsubscribe it is treated as possible event subscription imbalance. Another unique ability is to search for users of string literals which allows you to track users of a string constant which is not possible otherwise. For incremental builds the ShowRebuildTargets command can be used to identify the dependant targets that need a rebuild after you did compile one assembly. It has some heuristics in place to determine the impact of breaking changes and finds out which targets need to be recompiled as well. It has a ton of other features and a an API to access these things programmatically so you can build upon these simple queries create even better tools. Perhaps we get a Visual Studio plug in? You can download it from CodePlex here. It works via XCopy deployment. Simply let it run and check the command line help out. The best feature in my opinion is that the output of nearly all commands can be piped to Excel for further analysis. Since it does read also the pdbs it can show you the source file name and line number as well for all matches. The following picture shows the output of a –WhousesType query. The following command checks where type from BaseLibraryV1.dll are used inside DependantLibV1.dll. All matches are printed out with the reason and matching item along with file and line number. There is even a hyper link to the match which will open Visual Studio. ApiChange -whousestype "*" BaseLibraryV1.dll -in DependantLibV1.dll –excel The "*” is the actual query which means all types. The syntax is the same like in C# just that placeholders are allowed ;-). More info's can be found at the Codeplex Documentation.     The tool was developed in a TDD style manner which means that it is heavily tested and already used by a quite large user base inside the company I do work for. Luckily for you I got the permission to make it public so you take advantage of it. It is fully instrumented with tracing. If you find bugs simply add the –trace command line switch to find out what is failing and send me the output. How is it done? Your first guess might be that it uses reflection. Wrong. It is based on Mono Cecil a free IL parser with a fantastic API to access all internals of a managed assembly. The speed is awesome and to make it even faster I did make the tool heavily multi threaded. The query above did execute in 1.8s with the Excel output. On a rather slow machine I can analyze over 1500 assemblies in less than 40s with a very low memory consumption. The true power of Mono Cecil is that I can load an assembly like any other data file. I have no problems unloading a file but if I would have used reflection I would need to unload a whole AppDomain just to get rid of one assembly in my memory. Just to give you a glimpse how ApiChange.Api.dll can be used I show you one of the unit tests:           public void Can_Find_GenericMethodInvocations_With_Type_Parameters()         { // 1. Create an aggregator to collect our matches             UsageQueryAggregator agg = new UsageQueryAggregator();   // 2. This is the type we want to search for. Load it via the type query             var decimalType = TypeQuery.GetTypeByName(TestConstants.MscorlibAssembly, "System.Decimal");   // 3. register the type query which searches for uses of the Decimal type             new WhoUsesType(agg, decimalType);   // 4. Search for all users of the Decimal type in the DependandLibV1Assembly             agg.Analyze(TestConstants.DependandLibV1Assembly);   // Extract matches and assert             Assert.AreEqual(2, agg.MethodMatches.Count, "Method match count");             Assert.AreEqual("UseGenericMethod", agg.MethodMatches[0].Match.Name);             Assert.AreEqual("UseGenericMethod", agg.MethodMatches[1].Match.Name);         } Many thanks go from here to Jb Evian for the creation of Mono.Cecil. Without this fantastic piece of code it would have been much much harder. There are other options around like the Common Compiler Infrastructure  Metadata Api which should do the same thing but it was not a real option since the Microsoft reader did fail on even simple assemblies (at least in September 2009 this was the case). Besides this I found the CCI Apis much harder to use. The only real competitor was Reflector which does support many things but does not let me access his cool high level analyze commands. So I decided to dig into the IL specs and as a result you can query your compiled binaries from the command line or programmatically. The best thing is you try it out for yourself and give me some feedback what you miss. If you want to contribute or have a cool idea what should be added drop me a mail at A Kraus1@___No [email protected]. There is much more inside the tool I did not talk about it (yet).

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  • C# Exception when retrieving rows from a datagrid in virtual mode

    - by JamesM
    Hi all, I keep getting an exception (see below) when I retrieve a list of rows from a Virtual Mode datagrid, this only happens when I have more rows than I can display on screen and it doesn't happen every time. Is there anything I'm missing with regards to virtual mode? Update The image below shows the problem, the index is now outside the list range. The reason for this is say I have 10 items and I hide 5 as they are not needed and I want to run some code on the 5 that are visible, there are now 5 items but the index of some maybe between 5-9, how can I re-index? When I have run some code on the visible 5 I then show the hidden 5 so I don't want to disgard these, I'd need to reindex again when they are all visible. Many thanks.

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  • Example of tree.drop_mode with jQuery sortable anywhere

    - by fred
    Hello Everyone, I have a working tree of galleries next to a sortable list of image thumbnails. I've been vainly trying to set up the galleries tree so that users can add images to the galleries by dropping the sortable thumbnails on to the galleries tree. I've been told this requires drop_mode. All efforts to get it to work have failed and I can't really make heads or tails of the drop_mode documentation. I've sought out some working examples via Google of just such an application but have failed. Can anyone point me to a working example of either a draggable or sortable list that successfully drops on to a tree and passes along some parameters between the two? Thanks!

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  • How to detect generation loss of a transcoded audio.

    - by The Rook
    Lets say you have a 96 kbit mp3 and you Transcode the file into a 320 kbit mp3. How could you programmatically detect the original bit rate or quality? Generation loss is created because each time a lossy algorithm is applied new information will be deemed "unnecessary" and is discarded. How could an algorithm use this property to detect the transcoding of audio. 128 kbps LAME mp3 transcoded to 320 kbps LAME mp3 (I Feel You, Depeche Mode) 10.8 MB. This image was taken from the bottom of this site. The 2 tracks above look nearly identical, but the difference is enough to support this argument.

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  • Why is IE7 hiding my overflow when, as far as I can tell, all it's containing elements have overflow

    - by dougoftheabaci
    If you visit the site in question (haddongrant.com) and go to the Artwork section, if you click on an image and view it's stack in Safari, Chrome or Firefox you'll notice the images extend up and down the page, eventually disappearing over the edge. This is what you should be seeing. In Internet Explorer 7, however, the overflow gets cut off at some point before it ever gets to the end of the page. The problem is... I can't tell where! I've had a look and every containing element should show overflow. I don't know why IE7 isn't. Does anyone have any ideas where I might need to add an overflow-y:visible;?

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  • jQuery .queue() not working as expected

    - by Andrew
    The page in question is right here: http://s289116086.onlinehome.us/lawjournaltv/index.php I'm 90% of the way there, I'm just assuming there's an error with my syntax. Focus on the blue callout area with "Workers' Compensation" as the title: Basically, I've created a little slideshow there with the controls at the top and when you click on any of them both the callout and the background are to slide. As you can see it's working now, but the problem is that I want the new background to slide in over the old one. I've tried several things including the queue() method, delay(), and adding everything else to the animate() callback with no success (right now the background goes black and then the new image slides in). You guys have never let me down before, so I'm hoping this is an easy fix. Thanks in advance!

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  • Why do we (really) program to interfaces?

    - by Kyle Burns
    One of the earliest lessons I was taught in Enterprise development was "always program against an interface".  This was back in the VB6 days and I quickly learned that no code would be allowed to move to the QA server unless my business objects and data access objects each are defined as an interface and have a matching implementation class.  Why?  "It's more reusable" was one answer.  "It doesn't tie you to a specific implementation" a slightly more knowing answer.  And let's not forget the discussion ending "it's a standard".  The problem with these responses was that senior people didn't really understand the reason we were doing the things we were doing and because of that, we were entirely unable to realize the intent behind the practice - we simply used interfaces and had a bunch of extra code to maintain to show for it. It wasn't until a few years later that I finally heard the term "Inversion of Control".  Simply put, "Inversion of Control" takes the creation of objects that used to be within the control (and therefore a responsibility of) of your component and moves it to some outside force.  For example, consider the following code which follows the old "always program against an interface" rule in the manner of many corporate development shops: 1: ICatalog catalog = new Catalog(); 2: Category[] categories = catalog.GetCategories(); In this example, I met the requirement of the rule by declaring the variable as ICatalog, but I didn't hit "it doesn't tie you to a specific implementation" because I explicitly created an instance of the concrete Catalog object.  If I want to test the functionality of the code I just wrote I have to have an environment in which Catalog can be created along with any of the resources upon which it depends (e.g. configuration files, database connections, etc) in order to test my functionality.  That's a lot of setup work and one of the things that I think ultimately discourages real buy-in of unit testing in many development shops. So how do I test my code without needing Catalog to work?  A very primitive approach I've seen is to change the line the instantiates catalog to read: 1: ICatalog catalog = new FakeCatalog();   once the test is run and passes, the code is switched back to the real thing.  This obviously poses a huge risk for introducing test code into production and in my opinion is worse than just keeping the dependency and its associated setup work.  Another popular approach is to make use of Factory methods which use an object whose "job" is to know how to obtain a valid instance of the object.  Using this approach, the code may look something like this: 1: ICatalog catalog = CatalogFactory.GetCatalog();   The code inside the factory is responsible for deciding "what kind" of catalog is needed.  This is a far better approach than the previous one, but it does make projects grow considerably because now in addition to the interface, the real implementation, and the fake implementation(s) for testing you have added a minimum of one factory (or at least a factory method) for each of your interfaces.  Once again, developers say "that's too complicated and has me writing a bunch of useless code" and quietly slip back into just creating a new Catalog and chalking any test failures up to "it will probably work on the server". This is where software intended specifically to facilitate Inversion of Control comes into play.  There are many libraries that take on the Inversion of Control responsibilities in .Net and most of them have many pros and cons.  From this point forward I'll discuss concepts from the standpoint of the Unity framework produced by Microsoft's Patterns and Practices team.  I'm primarily focusing on this library because it questions about it inspired this posting. At Unity's core and that of most any IoC framework is a catalog or registry of components.  This registry can be configured either through code or using the application's configuration file and in the most simple terms says "interface X maps to concrete implementation Y".  It can get much more complicated, but I want to keep things at the "what does it do" level instead of "how does it do it".  The object that exposes most of the Unity functionality is the UnityContainer.  This object exposes methods to configure the catalog as well as the Resolve<T> method which is used to obtain an instance of the type represented by T.  When using the Resolve<T> method, Unity does not necessarily have to just "new up" the requested object, but also can track dependencies of that object and ensure that the entire dependency chain is satisfied. There are three basic ways that I have seen Unity used within projects.  Those are through classes directly using the Unity container, classes requiring injection of dependencies, and classes making use of the Service Locator pattern. The first usage of Unity is when classes are aware of the Unity container and directly call its Resolve method whenever they need the services advertised by an interface.  The up side of this approach is that IoC is utilized, but the down side is that every class has to be aware that Unity is being used and tied directly to that implementation. Many developers don't like the idea of as close a tie to specific IoC implementation as is represented by using Unity within all of your classes and for the most part I agree that this isn't a good idea.  As an alternative, classes can be designed for Dependency Injection.  Dependency Injection is where a force outside the class itself manipulates the object to provide implementations of the interfaces that the class needs to interact with the outside world.  This is typically done either through constructor injection where the object has a constructor that accepts an instance of each interface it requires or through property setters accepting the service providers.  When using dependency, I lean toward the use of constructor injection because I view the constructor as being a much better way to "discover" what is required for the instance to be ready for use.  During resolution, Unity looks for an injection constructor and will attempt to resolve instances of each interface required by the constructor, throwing an exception of unable to meet the advertised needs of the class.  The up side of this approach is that the needs of the class are very clearly advertised and the class is unaware of which IoC container (if any) is being used.  The down side of this approach is that you're required to maintain the objects passed to the constructor as instance variables throughout the life of your object and that objects which coordinate with many external services require a lot of additional constructor arguments (this gets ugly and may indicate a need for refactoring). The final way that I've seen and used Unity is to make use of the ServiceLocator pattern, of which the Patterns and Practices team has also provided a Unity-compatible implementation.  When using the ServiceLocator, your class calls ServiceLocator.Retrieve in places where it would have called Resolve on the Unity container.  Like using Unity directly, it does tie you directly to the ServiceLocator implementation and makes your code aware that dependency injection is taking place, but it does have the up side of giving you the freedom to swap out the underlying IoC container if necessary.  I'm not hugely concerned with hiding IoC entirely from the class (I view this as a "nice to have"), so the single biggest problem that I see with the ServiceLocator approach is that it provides no way to proactively advertise needs in the way that constructor injection does, allowing more opportunity for difficult to track runtime errors. This blog entry has not been intended in any way to be a definitive work on IoC, but rather as something to spur thought about why we program to interfaces and some ways to reach the intended value of the practice instead of having it just complicate your code.  I hope that it helps somebody begin or continue a journey away from being a "Cargo Cult Programmer".

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  • Where is the leak?

    - by Horatiu Paraschiv
    UIGraphicsBeginImageContext(targetSize); //instruments show here a leak 128bytes CGRect thumbnailRect = CGRectZero; thumbnailRect.origin = thumbnailPoint; thumbnailRect.size.width = scaledWidth; thumbnailRect.size.height = scaledHeight; [sourceImage drawInRect:thumbnailRect]; newImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); Hi I'm trying to scale a UIImage so I load it with [UIImage imageNamed:@"myImage.png"]; and then pass it into a method. In that method I have the code above that resizes my image and at the end of the method I have a return newImage; The instruments show me a leak at line UIGraphicsBeginImageContext(targetSize); //instruments show here a leak 128bytes What am I doing wrong? Where exactly is the leak?

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