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• Where to include business logic in a domain driven architecture

  - by Mike C.

  I'm trying to learn effective DDD practices as I go, but had a fundamental question I wanted to get some clarity on. I am using ASP.NET WebForms and I am creating a situation where a user places an order. Upon order submission, the code-behind retrieves the user, builds the order from the inputs on the form, calls the User.PlaceOrder() method to perform add the order object to the user's order collection, and calls the repository to save the record to the database. That is fairly simply and straightforward. Now I need to add logic to send an order confirmation email, and I'm not really sure the proper place to put this code or where to call it. In the olden days I would simply put that code in the code-behind and call it at the same time I was building the order, but I want to get a step closer to solid proper architecture so I wanted to get some information. Thanks for your help!

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• As a programmer what single discovery has given you the greatest boost in productivity?

  - by ChrisInCambo

  This question has been inspired by my recent discovery/adoption of distributed version control. I started using it (mercurial) just because I liked the idea of still being able to make commits at times when I couldn't connect to the central server. I never expected it would give me a large boost in general productivity, but a pleasant side effect I discovered was that making a new clone every time I started a new task and giving that clone a descriptive folder name is extremely effective at keeping me on task resulting is a noticeable productivity increase. So as a programmer what single discovery has given you the greatest boost in productivity? Extra respect for answers which involve tools or practices that aren't so obvious from the outside!

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• Extracting DCT coefficients from encoded images and video

  - by misha

  Is there a way to easily extract the DCT coefficients (and quantization parameters) from encoded images and video? Any decoder software must be using them to decode block-DCT encoded images and video. So I'm pretty sure the decoder knows what they are. Is there a way to expose them to whomever is using the decoder? I'm implementing some video quality assessment algorithms that work directly in the DCT domain. Currently, the majority of my code uses OpenCV, so it would be great if anyone knows of a solution using that framework. I don't mind using other libraries (perhaps libjpeg, but that seems to be for still images only), but my primary concern is to do as little format-specific work as possible (I don't want to reinvent the wheel and write my own decoders). I want to be able to open any video/image (H.264, MPEG, JPEG, etc) that OpenCV can open, and if it's block DCT-encoded, to get the DCT coefficients. In the worst case, I know that I can write up my own block DCT code, run the decompressed frames/images through it and then I'd be back in the DCT domain. That's hardly an elegant solution, and I hope I can do better. Presently, I use the fairly common OpenCV boilerplate to open images: IplImage *image = cvLoadImage(filename); // Run quality assessment metric The code I'm using for video is equally trivial: CvCapture *capture = cvCaptureFromAVI(filename); while (cvGrabFrame(capture)) { IplImage *frame = cvRetrieveFrame(capture); // Run quality assessment metric on frame } cvReleaseCapture(&capture); In both cases, I get a 3-channel IplImage in BGR format. Is there any way I can get the DCT coefficients as well?

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• Emulating a transaction-safe SEQUENCE in MySQL

  - by Michael Pliskin

  We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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• Manage bad_alloc exception in C++ construtor

  - by Jimmy zhang

  I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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• Design advices for quick navigation between view

  - by Thomas Joulin

  Usually, when a View requires a lot of bindings, or some UI Elements like a Bing Map, it takes a "while" to load (like between half a second and a second). I don't want a delay between a "tap" action (like tapping an element on a ListBox) and the navigation action (displaying a new page). I don't mind displaying the page progressively. For example, for a Bing Map, I don't mind displaying a black page with only a title, and a second later, having the Map appear. What are the best practices ? It could post a sample if i'm not clear enough

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• Three Java classes: point out all the issues you can find!

  - by Sicarius

  I wrote three classes for a colleague of mine (I'm new at this job). They compile just fine, but he tells me there are "defects, bugs, and style problems." He wants me to print the files out and mark the problems such as the standard coding conventions, best practices, format, design, and logic. I wrote this code when I was extremely tired and I plan to rewrite it completely. My mistake was showing to it before looking it over myself again. However, he still wants me to do the markings on paper. Any input is greatly appreciated! The three Java classes ['Station.java', 'ParserInt.java', 'ParserException.java'] are uploaded here: http://www.megaupload.com/?d=N2CUVSV2

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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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• Python: Data Object or class

  - by arg20

  I enjoy all the python libraries for scraping websites and I am experimenting with BeautifulSoup and IMDB just for fun. As I come from Java, I have some Java-practices incorporated into my programming styles. I am trying to get the info of a certain movie, I can either create a Movie class or just use a dictionary with keys for the attributes. My question is, should I just use dictionaries when a class will only contain data and perhaps almost no behaviour? In other languages creating a type will help you enforce certain restrictions and because of type checks the IDE will help you program, this is not always the case in python, so what should I do? Should I resort to creating a class only when there's both, behaviour and data? Or create a movie class even though it'll probably be just a data container? This all depends on your model, in this particular case either one is fine but I'm wondering about what's a good practice.

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• iOS sample projects to learn from

  - by DerMike

  I am just starting iOS development. I read some tutorials, watched stuff on iTunes U and wrote some sample code myself. Now I want to take the next step. I want to learn about best practices for iOS development in XCode. Are there any well written and well organized iOS projects that one could take a look at? (As I see it, iOS is not exactly the place for open source enthusiasts, however.) Thanks Mike.

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• Best way to carry & modify a variable through various instances and functions?

  - by bobsoap

  I'm looking for the "best practice" way to achieve a message / notification system. I'm using an OOP-based approach for the script and would like to do something along the lines of this: if(!$something) $messages->add('Something doesn\'t exist!'); The add() method in the messages class looks somewhat like this: class messages { public function add($new) { $messages = $THIS_IS_WHAT_IM_LOOKING_FOR; //array $messages[] = $new; $THIS_IS_WHAT_IM_LOOKING_FOR = $messages; } } In the end, there is a method in which reads out $messages and returns every message as nicely formatted HTML. So the questions is - what type of variable should I be using for $THIS_IS_WHAT_IM_LOOKING_FOR? I don't want to make this use the database. Querying the db every time just for some messages that occur at runtime and disappear after 5 seconds just seems like overkill. Using global constants for this is apparently worst practice, since constants are not meant to be variables that change over time. I don't even know if it would work. I don't want to always pass in and return the existing $messages array through the method every time I want to add a new message. I even tried using a session var for this, but that is obviously not suited for this purpose at all (it will always be 1 pageload too late). Any suggestions? Thanks!

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• Php string handling triks

  - by Dam

  Hi my question Need to get the 10 word before and 10 words after for the given text . i mean need to start the 10 words before the keyword and end with 10 word after the key word. Given text : "Twenty-three" The main trick : content having some html tags etc .. tags need to keep that tag with this content only . need to display the words from 10before - 10after content is bellow : <div id="hpFeatureBoxInt"><h3><a href="/go/homepage/i/int/news/world/1/-/news/1/hi/world/europe/8592190.stm">Suicide bombings hit Moscow Metro</a></h3><p>Past suicide bombings in Moscow have been blamed on Islamist rebels At least 35 people have been killed after two female suicide bombers blew themselves up on Moscow Metro trains in the morning rush hour,<h2><span class="dy">Top News Story</span></h2> officials say.<img height="150" width="201" alt="Emergency services carry a body from a Metro station in Moscow (29 March 2010)" src="http://wwwimg.bbc.co.uk/feedengine/homepage/images/_47550689_moscowap203_201x150.jpg">Twenty-three died in the first blast at 0756 (0356 GMT) as a<a href="#"> train stood </a>at the central Lubyanka station, beneath the offices of the FSB intelligence agency.About 40 minutes later, a second explosion ripped through a train at Park Kultury, leaving another 12 dead.No-one has said they carried out the worst attack in the capital since 2004. </p><p id="fbilisten"><a href="/go/homepage/i/int/news/heading/-/news/">More from BBC News</a></p></div> Thank you

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• Optional URL fragment in Codeigniter?

  - by DA

  This is maybe a simple syntax question or possibly a best-practices question in terms of codeigniter. I should start by saying I'm not a PHP or Codeigniter person so trying to get up to speed on helping on a project. I've found the CI documentation fairly good. The one question I can't find an answer to is how to make part of a URL optional. An example the CI documentation uses is this: example.com/index.php/products/shoes/sandals/123 and then the function used to parse the URI: function shoes($sandals, $id) For my example, I'd like to be able to modify the URL as such: example.com/index.php/products/shoes/all So, if no ID is passed, it's just ignored. Can that be done? Should that be done? A second question unrelated to my problem but pertaining to the example above, why would the variable $sandals be used as in the example, the value is 'sandals'? Shouldn't that variable be something like $shoetype?

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• Basic Python: Exception raising and local variable scope / binding

  - by SuperJdynamite

  I have a basic "best practices" Python question. I see that there are already StackOverflow answers tangentially related to this question but they're mired in complicated examples or involve multiple factors. Given this code: #!/usr/bin/python def test_function(): try: a = str(5) raise b = str(6) except: print b test_function() what is the best way to avoid the inevitable "UnboundLocalError: local variable 'b' referenced before assignment" that I'm going to get in the exception handler? Does python have an elegant way to handle this? If not, what about an inelegant way? In a complicated function I'd prefer to avoid testing the existence of every local variable before I, for example, printed debug information about them.

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• What happens to an instance of ServerSocket blocked inside accept(), when I drop all references to i

  - by Hanno Fietz

  In a multithreaded Java application, I just tracked down a strange-looking bug, realizing that what seemed to be happening was this: one of my objects was storing a reference to an instance of ServerSocket on startup, one thread would, in its main loop in run(), call accept() on the socket while the socket was still waiting for a connection, another thread would try to restart the component under some conditions, the restart process missed the cleanup sequence before it reached the initialization sequence as a result, the reference to the socket was overwritten with a new instance, which then wasn't able to bind() anymore the socket which was blocking inside the accept() wasn't accessible anymore, leaving a complete shutdown and restart of the application as the only way to get rid of it. Which leaves me wondering: with no references left to the ServerSocket instance, what would free the socket for a new connection? At what point would the ServerSocket become garbage collected? In general, what are good practices I can follow to avoid this type of bug?

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• What is the best to format messages for queueing?

  - by Tijmen

  I've been reading up on message queueing lately, and I'd like to implement a simple, extendable, system for my app. While there's a lot of good information on the subject of setting up a MQ system out there, I can't find a lot about the actual implementation. I'm looking for patterns and best practices on how to properly format messages for a queue, and ways to execute the jobs in PHP. Should I use JSON, serialized objects, text, URLs or XML? What information should I send? Is a worker with a switch($job['command']) {} (or something like that) the way to go, or are there any established patterns out there to implement a worker? Help greatly appreciated!

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• jQuery: what is it "forbidden" to do in plain Javascript

  - by flybywire

  A jQuery best practices question. I am writing a very jQuery intensive web page. I am new to jQuery and notice its power, but as I come with heavy javascript experience and knowledge, my question is: What should be done in jQuery and what in plain javascript. For example, there are callbacks that send a plain DOM object as an argument. Should I use that or should I wrap it ( like $(this)). Does it matter if I do this.x=y or $(this).attr("x", y).

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• What programming languages do you consider indispensable in your experience?

  - by Federico Ramponi

  Each programming language comes with its concepts, best practices, libraries, tools, community, in one word: culture. Learning more than one programming language will make you a better programmer, for the more concepts you learn, the faster you will feel comfortable when the next language or technology will come. Mine, so far, are C, some C++, and Python, and many times I read that it would be worth learning LISP, for "the profound enlightenment experience you will have when you finally get it" (quoting Eric Raymond). My questions are: Which is the next one you would consider a good investment to learn? Of the many programming languages you have learnt and worked with, which ones do you consider to be an essential part of one's CS culture, and why? EDIT. Further question: is there any language you would sincerely advise to avoid as a waste of time? (The famous, and questionable, slatings in this letter from Dijkstra come to my mind.)

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• Directory layout for a Python project with C extension modules

  - by Kamil Kisiel

  We have numerous projects in our organization that are mixed Python/C. Currently we're trying to standardize on a directory layout for our projects and are trying to come up with a convenient scheme. One point of contention is where to put C extension modules in the tree. We're tossing around a couple of options (relative to project root): ./src/package/subpackage/module.c or alongside the python modules in the package tree: ./package/subpackage/module.c or in a src directory in the subpackage: ./package/subpackage/src/module.c One reason for keeping them out of the package directories could be because it will lead to clutter, especially if there are other .c and .h files which aren't themselves modules but still need to be compiled. Also in the "integrated" scheme, what do you do with headers and files that are used by more than one module? Put them in a common top-level directory? I'd be interested to know what other people are using, or if there are any established best practices for this.

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• List show/add/remove View

  - by Michael

  Looking for some best practices of UI list on iPhone which has item add/modify/delete functions. Please refer to some sample codes or articles to build user friendly interface. The main application is tab bar application and one of the tabs supposed to show item management. The item itself consisting of 3 text items, first one can be label, it's short, the rest if it's not terribly complicated I would like to show below with small font or show when user taps on item entering edit mode... Not sure how to design all this and which views to use.

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• How to set the ReturnUrl for the Login link in MVC 3 app?

  - by user762196

  using System; using Microsoft.Practices.Unity; namespace <MyNameSpace> { public class UrlFactory { public static UrlFactory Current { get { return HttpApplicationUnityContext.Current.Resolve<UrlFactory>(); } } public string GetLoginUrl() { return String.Format("{0}/login?ReturnUrl={1}", MyConfig.BaseHttpUrl, <GET_PAGE_URL>); } } The user can be on any page on the site and click the Login link. But the ReturnUrl must always point to the exact page where he clicked it. I must take the user back to the page he clicked the login link. In my code above, how do I get the page url in <GET_PAGE_URL>? Thanks

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• Time complexity of a powerset generating function

  - by Lirik

  I'm trying to figure out the time complexity of a function that I wrote (it generates a power set for a given string): public static HashSet<string> GeneratePowerSet(string input) { HashSet<string> powerSet = new HashSet<string>(); if (string.IsNullOrEmpty(input)) return powerSet; int powSetSize = (int)Math.Pow(2.0, (double)input.Length); // Start at 1 to skip the empty string case for (int i = 1; i < powSetSize; i++) { string str = Convert.ToString(i, 2); string pset = str; for (int k = str.Length; k < input.Length; k++) { pset = "0" + pset; } string set = string.Empty; for (int j = 0; j < pset.Length; j++) { if (pset[j] == '1') { set = string.Concat(set, input[j].ToString()); } } powerSet.Add(set); } return powerSet; } So my attempt is this: let the size of the input string be n in the outer for loop, must iterate 2^n times (because the set size is 2^n). in the inner for loop, we must iterate 2*n times (at worst). 1. So Big-O would be O((2^n)*n) (since we drop the constant 2)... is that correct? And n*(2^n) is worse than n^2. if n = 4 then (4*(2^4)) = 64 (4^2) = 16 if n = 100 then (10*(2^10)) = 10240 (10^2) = 100 2. Is there a faster way to generate a power set, or is this about optimal?

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• How painful is a django project upload to a live (staging) site?

  - by Ignacio

  Hi, I've getting quite fast with a small django project of mine, which I'm developing locally, of course. But, as I had never worked with django before, I'm not aware of what it implies to upload it and test it on a production server. And I'm quite curious, since I'm very eager to test an early release live. I know there is this document, which I think it'll be really helpful: http://djangobook.com/en/2.0/chapter12/ But, are there any details I should take into account before, during and after the deployment? Any advice or best practices? Thanks.

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• Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

  - by user1459698

  I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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• ok.. what's with this 'var' thing in C#?? [closed]

  - by KevinDeus

  Possible Duplicate: Use of var keyword in C# I have ReSharper, which is a pretty good tool to remind me of some good programming practices.. for example it always recommends that I use the most narrowed convention I can use when passing variables to functions (such as recommending IEnumerable instead of List when I fail to use any of List's specific function. Awesome. However, one of its new behaviors (for C# 4.0) is to remind me at every opportunity to use 'var' when declaring variables. Now I know that there are some valid uses of 'var', but do I really want to use it all the time? I'm sure that ReSharper has a reason for this, but I can't figure it out.. for me it makes the code less readable..

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