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• Validation - Data Integrity

  - by Thomas

  A table can only store 10 records in a particular state, 10 users over 30 years for example, the others must be less than 30 years. It is a business rule and as such should be respected. How to ensure that state? Think: multiple users accessing this table.

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• Is it considered bad practice to have ViewModel objects hold the Dispatcher?

  - by stiank81

  My WPF application is structured using the MVVM pattern. The ViewModels will communicate asynchronously with a server, and when the requested data is returned a callback in the ViewModel is triggered, and it will do something with this data. This will run on a thread which is not the UI Thread. Sometimes these callbacks involve work that needs to be done on the UI thread, so I need the Dispatcher. This might be things such as: Adding data to an ObservableCollection Trigger Prism commands that will set something to be displayed in the GUI Creating WPF objects of some kind. I try to avoid the latter, but the two first points here I find to be reasonable things for ViewModels to do. So; is it okay to have ViewModels hold the Dispatcher to be able to Invoke commands for the UI thread? Or is this considered bad practice? And why?

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• Using a message class static method taking in an action to wrap Try/Catch

  - by Chris Marisic

  I have a Result object that lets me pass around a List of event messages and I can check whether an action was successful or not. I've realized I've written this code in alot of places Result result; try { //Do Something ... //New result is automatically a success for not having any errors in it result = new Result(); } catch (Exception exception) { //Extension method that returns a Result from the exception result = exception.ToResult(); } if(result.Success) .... What I'm considering is replacing this usage with public static Result CatchException(Action action) { try { action(); return new Result(); } catch (Exception exception) { return exception.ToResult(); } } And then use it like var result = Result.CatchException(() => _model.Save(something)); Does anyone feel there's anything wrong with this or that I'm trading reusability for obscurity?

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• Can I use an abstract class instead of a private __construct() when creating a singleton in PHP?

  - by Pheter

  When creating a Singleton in PHP, I ensure that it cannot be instantiated by doing the following: class Singleton { private function __construct() {} private function __clone() {} public static function getInstance() {} } However, I realised that defining a class as 'abstract' means that it cannot be instantiated. So is there anything wrong with doing the following instead: abstract class Singleton { public static function getInstance() {} } The second scenario allows me to write fewer lines of code which would be nice. (Not that it actually makes much of a difference.)

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• What do you do in your source control repository when you start a rewrite of a program?

  - by Max Schmeling

  I wrote an application a while back and have been maintaining it for a while now, but it's gotten to the point where there's several major new features to be added, a ton of changes that need made, and I know quite a few things I could do better, so I'm starting a rewrite of the entire program (using bits and pieces from original). My question is, what do you do with SVN at this point? Should I put the new version somewhere else, or should I delete the files I no longer need, add the new files, and just treat it like normal development in SVN? How have you handled this in the past?

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• What Quick Fixes Make You Queasy When You Code Them?

  - by KevDog

  We've all done them, the short fix that will get the system back up and running until we can Do The Right Thing. What have you marked in your code with the dreaded //Hack comment?

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• what if i keep my class members are public?

  - by anish

  In c++ instance variables are private by default,in Python variables are public by default i have two questions regarding the same:- 1: why Python have all the members are public by default? 2: People say you should your member data should be private what if i make my data to be public? what are the disadvantages of this approch? why it is a bad design?

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• jquery best controls that generated tree

  - by mazhar

  ok can someone tell me the best tree view control in jquery? apart from dynatree

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• Multiple steps form. All-in-one or multiple web pages.

  - by Andrew Florko

  Is it preferable to develop multiple steps form (80+ fields grouped into 5 steps) as single web page (tabbed) compared to page-per-step approach if users tend to complete form when started to populate? What are draw-backs big single page and page-per-step forms usually have? Thank you in advance!

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• Is there any difference between var name = function() {} & function name() {} in Javascript?

  - by Fletcher Moore

  Suppose we are inside a function and not in the global namespace. function someGlobalFunction() { var utilFunction1 = function() { } function utilFunction2 () { } utilFunction1(); utilFunction2(); } Are these synonymous? And do these functions completely cease to exist when someGlobalFunction returns? Should I prefer one or the other for readability or some other reason?

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• Double use of variables?

  - by Vaccano

  I have read that a variable should never do more than one thing. Overloading a variable to do more than one thing is bad. Because of that I end up writing code like this: (With the customerFound variable) bool customerFound = false; Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; customerFound = true; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; customerFound = true; } } } if (customerFound) { // Do something } But deep down inside, I sometimes want to write my code like this: (Without the foundCustomer variable) Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; } } } if (foundCustomer != null) { // Do something } Does this secret desires make me an evil programmer? (i.e. is the second case really bad coding practice?)

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• Correct way to protect a private API key when versioning a python application on a public git repo

  - by systempuntoout

  I would like to open-source a python project on Github but it contains an API key that should not be distributed. I guess there's something better than removing the key each time a "push" is committed to the repo. Imagine a simplified foomodule.py : import urllib2 API_KEY = 'XXXXXXXXX' urllib2.urlopen("http://example.com/foo?id=123%s" % API_KEY ).read() What i'm thinking is: Move the API_KEY in a second key.py module importing it on foomodule.py; i would then add key.py on .gitignore file. Same as 1 but using ConfigParser Do you know a good programmatic way to handle this scenario?

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• Generating new tasks in a foreach loop

  - by Scott Chamberlain

  I know from the codeing guidlines that I have read you should not do for (int i = 0; i < 5; i++) { Task.Factory.StartNew(() => Console.WriteLine(i)); } Console.ReadLine(); as it will write 5 5's, I understand that and I think i understand why it is happening. I know the solution is just to do for (int i = 0; i < 5; i++) { int localI = i; Task.Factory.StartNew(() => Console.WriteLine(localI)); } Console.ReadLine(); However is something like this ok to do? Task currentTask = myFirstTask; currentTask.Start(); foreach (Task task in _TaskList) { currentTask.ContinueWith((antecendent) => { if(antecendent.IsCompleated) { task.Start(); } else //do error handling; }); currentTask = task; } } or do i need to do this? Task currentTask = myFirstTask; foreach (Task task in _TaskList) { Task localTask = task; currentTask.ContinueWith((antecendent) => { if(antecendent.IsCompleated) { localTask.Start(); } else //do error handling; }); currentTask = task; }

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• jquery: How to deal with 'this' in ajax callbacks

  - by Svish

  I currently have code similar to this for a form: $('#some-form') .submit(function() { // Make sure we are not already busy if($(this).data('busy')) return false; $(this).data('busy', true); // Do post $.post("some/url", $(this).serialize(), function(data) { if(data.success) // Success is a boolean I set in the result on the server { // Deal with data } else { // Display error } $('#some-form') .removeData('busy'); }); return false; }); My issue is that I would like to somehow remove the need for knowing the form id in the post callback. In the end where I remove the busy data from the form, I'd like to somehow not have that hard coded. Is there any way I can do this? Is there a way I can hand whatever is in this to the post callback function? Since I know the id right now, I can get around it by doing what I have done, but I'd like to know how to not be dependant on knowing the id, since often I don't have an id. (For example if I have a link in each row in a table and all the rows have the same click handler.

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• Is it bad practice to use a C header instead of its C++ equivalent in C++ (e.g. stdio.h instead of c

  - by Maulrus

  It seems that a lot of people include example.h instead of cexample in their C++ code. I know that everything in the C++ versions is declared in namespace std, but I'm not aware of any other differences. So why do people use the C headers, and is it okay to do so?

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• What is the advantage of placing "{" on the same line as a conditional statement?

  - by DrLazer

  I have kind of got used to it now but in the past if i had to work on a piece of code someone else had written with the brackets placed in this way I would have to go through and change it all. Why would anybody do this, I can't think of a single advantage but lots of disadvantages.

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• 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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• Correct approach to validate attributes of an instance of class

  - by systempuntoout

  Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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• Is this SQL select code following good practice?

  - by acidzombie24

  I am using sqlite and will port to mysql (5) later. I wanted to know if I am doing something I shouldnt be doing. I tried purposely to design so I'll compare to 0 instead of 1 (I changed hasApproved to NotApproved to do this, not a big deal and I haven't written any code). I was told I never need to write a subquery but I do here. My Votes table is just id, ip, postid (I don't think I can write that subquery as a join instead?) and that's pretty much all that is on my mind. Naming conventions I don't really care about since the tables are created via reflection and is all over the place. select id, name, body, upvotes, downvotes, (select 1 from UpVotes where IPAddr=? AND post=Post.id) as myup, (select 1 from DownVotes where IPAddr=@0 AND post=Post.id) as mydown from Post where flag = '0' limit ?, ?"

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• To change checkbox text or to not change?

  - by Axarydax

  Hi, I'm having an argument with a co-worker, and I'm trying to convince him that it's a bad idea to change checkbox text (label) according to the checkbox state. For example, we have a combobox that automatically picks selected value (and is disabled) when checkbox next to it is checked and is enabled when checkbox is cleared. His idea is to show Autoselect when checkbox is checked and Manual select when it's cleared. I'm sure that this will confuse the user as users tend to think that checking a checkbox next to a verb will make it true, only to find that the label has changed to something else. What is your opinion on this matter? P.S. I remember reading about changing checkbox text somewhere, in a book or blog article, but can't remember where. It would be great to have this in writing :-)

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• The Wheel Invention - Beneficial For Learning?

  - by Sarfraz

  Hello, Chris Coyier of css-tricks.com has written a good article titled Regarding Wheel Invention. In a paragraph he says: On the “reinventing” side, you benefit from complete control and learning from the process. And on the very next line he says: On the other side, you benefit from speed, reliability, and familiarity. Also often at odds are time spent and cost. He is right in both statements I think. I really like his first statement. I do actually sometimes re-invent the wheel to learn more and gain complete control over what I am inventing. I wonder why people are so much against that or rather biased. Isn't there the benefit of learning and getting complete control or probably some other benefits too. I would love to see what you have to say about this.

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• Patterns for avoiding jQuery silent fails

  - by Matias

  Is there any good practice to avoid your jQuery code silently fail? For example: $('.this #is:my(complexSelector)').doSomething(); I know that every time this line get executed, the selector is intended to match at least one element, or certain amount of elements. Is there any standard or good way to validate that? I thought about something like this: var $matchedElements = $('.this #is:my(complexSelector)'); if ($matchedElements.length < 0) throw 'No matched elements'; $matchedElements.doSomething(); Also I think unit testing would be a valid option instead of messing the code. My question may be silly, but I wonder whether there is a better option than the things that I'm currently doing or not. Also, maybe I'm in the wrong way checking if any element match my selector. However, as the page continues growing, the selectors could stop matching some elements and pieces of functionality could stop working inadvertently.

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• Sys. engineer has decided to dynamically transform all XSLs into DLLs on website build process. DLL

  - by John Sullivan

  Hello, OS: Win XP. Here is my situation. I have a browser based application. It is "wrapped" in a Visual Basic application. Our "Systems Engineer Senior" has decided to spawn DLL files from all of our XSL pages (many of which have duplicate names) upon building a new instance of the website and have the active server pages (ASPX) use the DLL instead. This has created a "known issue" in which ~200 DLL naming conflicts occur and, thus, half of our application is broken. I think a solution to this problem is that, thankfully, we're generating the names of the DLLs and linking them up with our application dynamically. Therefore we can do something kludgy like generate a hash and append it to the end of the DLL file name when we build our website, then always reference the DLL that had some kind of random string / hash appended to its name. Aside from outright renaming the DLLs, is there another way to have multiple DLLs with the same name register for one application? I think the answer is "No, only between different applications using a special technique." Please confirm. Another question I have on my mind is whether this whole idea is a good practice -- converting our XSL pages (which we use in mass -- every time a response from our web app occurs) into DLL functions that call a "function" to do what the XSL page did via an active server page (ASPX), when we were before just sending an XML response to an XSL page via aspx.

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• 'goto' usage

  - by Landon

  I've long been under the impression that 'goto' should never be used if possible. While perusing libavcodec (which is written in C) the other day, I noticed multiple uses of it. Is it ever advantageous to use 'goto' in a language that supports loops and functions? If so, why?

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• CSS Brace Styles

  - by Nimbuz

  I'm unable to figure how the standard (or just popular) brace style names apply to CSS. Here're all the brace styles: /* one - pico? */ selector { property: value; property: value; } /* two */ selector { property: value; /* declaration starts on newline */ property: value; } /* three */ selector { property: value; property: value; } /* four - Allman or GNU?*/ selector { property: value; /* declaration starts on newline */ property: value; }? /* five */ selector { property: value; property: value; } /* six - horstmann? */ selector { property: value; /* declaration starts on newline */ property: value; } /* seven - banner?*/ selector { property: value; property: value; } /* eight */ selector { property: value; /* declaration starts on newline */ property: value; } Can someone please name each brace style for me? Many thanks!

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