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• C++, throw exception from initializer list

  - by aaa

  hello. what is the best way to throw exception from initializer list? for example: class C { T0 t0; // can be either valid or invalid, but does not throw directly T1 t1; // heavy object, do not construct if t0 is invalid, by throwing before C(int n) : t0(n), // throw exception if t0(n) is not valid t1() {} }; I thought maybe making wrapper, e.g. t0(throw_if_invalid(n)). What is the practice to handle such cases? Thanks

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• Hyphens or underscores in CSS and HTML identifiers?

  - by Török Gábor

  As both hyphen (-) and underscore (_) are valid characters in CSS and HTML identifiers, what are the advantages and disadvantages using one or the other? I prefer writing CSS class names with hyphens (e.g. field-text) and underscores for IDs (e.g. featured_content). Is there a best practice or it's only the matter of taste?

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• Best Practice for Uploading Many (2000+) Images to A Server

  - by bob

  Hello, I have a general question about this. When you have a gallery, sometimes people need to upload 1000's of images at once. Most likely, it would be done through a .zip file. What is the best way to go about uploading this sort of thing to a server. Many times, server have timeouts etc. that need to be accounted for. I am wondering what kinds of things should I be looking out for and what is the best way to handle a large amount of images being uploaded. I'm guessing that you would allow a user to upload a zip file (assuming the timeout does not effect you), and this zip file is uploaded to a specific directory, lets assume in this case a directory is created for each user in the system. You would then unzip the directory on the server and scan the user's folder for any directories containing .jpg or .png or .gif files (etc.) and then import them into a table accordingly. I'm guessing labeled by folder name. What kind of server side troubles could I run into? I'm aware that there may be many issues. Even general ideas would be could so I can then research further. Thanks! Also, I would be programming in Ruby on Rails but I think this question applies accross any language.

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• Example with Visitor Pattern

  - by devoured elysium

  public class Song { public string Genre { get; protected set; } public string Name { get; protected set; } public string Band { get; protected set; } public Song(string name, string band, string genre) { Name = name; Genre = genre; Band = band; } } public interface IMusicVisistor { void Visit(List<Song> items); } public class MusicLibrary { List<Song> _songs = new List<Song> { ...songs ... }; public void Accept(IMusicVisitor visitor) { visitor.Visit(_songs); } } and now here's one Visitor I made: public class RockMusicVisitor : IMusicVisitor { public List<Song> Songs { get; protected set; } public void Visit(List<Song> items) { Songs = items.Where(x => x.Genre == "Rock").ToList(); } } Why is this any better than just putting a public property Songs and then letting any kind of class do with it anything that it wants to? This example comes from this post.

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• Should I be relying on WebTests for data validation?

  - by Alexander Kahoun

  I have a suite of web tests created for a web service. I use it for testing a particular input method that updates a SQL Database. The web service doesn't have a way to retrieve the data, that's not its purpose, only to update it. I have a validator that validates the response XML that the web service generates for each request. All that works fine. It was suggested by a teammate that I add data validation so that I check the database to see the data after the initial response validator runs and compare it with what was in the input request. We have a number of services and libraries that are separate from the web service I'm testing that I can use to get the data and compare it. The problem is that when I run the web test the data validation always fails even when the request succeeds. I've tried putting the thread to sleep between the response validation and the data validation but to no avail; It always gets the data from before the response validation. I can set a break point and visually see that the data has been updated in the DB, funny thing is when I step through it in debug with the breakpoint it does validate successfully. Before I get too much more into this issue I have to ask; Is this the purpose of web tests? Should I be able to validate data through service calls in this manner or am I asking too much of a web test and the response validation is as far as I should go?

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• Reordering arguments using recursion (pro, cons, alternatives)

  - by polygenelubricants

  I find that I often make a recursive call just to reorder arguments. For example, here's my solution for endOther from codingbat.com: Given two strings, return true if either of the strings appears at the very end of the other string, ignoring upper/lower case differences (in other words, the computation should not be "case sensitive"). Note: str.toLowerCase() returns the lowercase version of a string. public boolean endOther(String a, String b) { return a.length() < b.length() ? endOther(b, a) : a.toLowerCase().endsWith(b.toLowerCase()); } I'm very comfortable with recursions, but I can certainly understand why some perhaps would object to it. There are two obvious alternatives to this recursion technique: Swap a and b traditionally public boolean endOther(String a, String b) { if (a.length() < b.length()) { String t = a; a = b; b = t; } return a.toLowerCase().endsWith(b.toLowerCase()); } Not convenient in a language like Java that doesn't pass by reference Lots of code just to do a simple operation An extra if statement breaks the "flow" Repeat code public boolean endOther(String a, String b) { return (a.length() < b.length()) ? b.toLowerCase().endsWith(a.toLowerCase()) : a.toLowerCase().endsWith(b.toLowerCase()); } Explicit symmetry may be a nice thing (or not?) Bad idea unless the repeated code is very simple ...though in this case you can get rid of the ternary and just || the two expressions So my questions are: Is there a name for these 3 techniques? (Are there more?) Is there a name for what they achieve? (e.g. "parameter normalization", perhaps?) Are there official recommendations on which technique to use (when)? What are other pros/cons that I may have missed?

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• Looking for exercises to learn SQL, using the Northwind database

  - by MedicineMan

  I am trying to become more familiar with SQL by writing queries against the Northwind database. I am looking for some exercises that would help me to learn SQL and features of SQL Server. It is important that the exercises have solutions, and in complicated cases, it would be great if there was an explanation for the query. Thanks for the answers so far but I still have not found what I am looking for: Is there any free resource, available online, without registration, that I can find a list of these exercises?

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• When to use a routing rule vs query string parameters with asp.net mvc

  - by mwright

  We're considering moving forward with a ASP.NET MVC project and the subject of routing versus parameters came up. Seeing as how you can easily set up either or a combination of both in ASP.NET MVC, are there any considerations that I should be aware of when using one or the other?

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• What is your strategy to avoid dynamic typing errors in Python (NoneType has no attribute x)?

  - by Koen Bok

  Python is one of my favorite languages, but I really have a love/hate relationship with it's dynamicness. Apart from the advantages, it often results in me forgetting to check a type, trying to call an attribute and getting the NoneType (or any other) has no attribute x error. A lot of them are pretty harmless but if not handled correctly they can bring down your entire app/process/etc. Over time I got better predicting where these could pop up and adding explicit type checking, but because I'm only human I miss one occasionally and then some end-user finds it. So I'm interested in your strategy to avoid these. Do you use type-checking decorators? Maybe special object wrappers? Please share...

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• how to aviod infinite loop in observer pattern?

  - by joseph

  Hello. I have only one class with many instances. Every instance is observer of couple of other instances. As well every instance can be observable by couple of another instances. How to avoid infinite loop of calling update() in observers?

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• Empty data problem - data layer or DAL?

  - by luckyluke

  I designing the new App now and giving the following question a lot of thought. I consume a lot of data from the warehouse, and the entities have a lot of dictionary based values (currency, country, tax-whatever data) - dimensions. I cannot be assured though that there won't be nulls. So I am thinking: create an empty value in each of teh dictionaries with special keyID - ie. -1 do the ETL (ssis) do the correct stuff and insert -1 where it needs to let the DAL know that -1 is special (Static const whatever thing) don't care in the code to check for nullness of dictionary entries because THEY will always have a value But maybe I should be thinking: import data AS IS let the DAL do the thinking using empty record Pattern still don't care in the code because business layer will have what it needs from DAL. I think is more of a approach thing but maybe i am missing something important here... What do You think? Am i clear? Please don't confuse it with empty record problem. I do use emptyCustomer think all the time and other defaults too.

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• effective retrieve for a voting system in PHP and MySQL

  - by Adnan

  Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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• How do I remove a folder from Windows Distributed File System?

  - by digiguru

  We recently moved to a webfarm and setup dfs, only to find a beta application was creating files like there was no tomorrow. 1.2 million files were replicated across the farm, and since then we have prevented the application from creating new files, but every time we try to remove the files, it replaces them on each server because of replication. The process of replacing them actually causes to server to run slowly and in some cases stall. Is there any way we can stop replication at a folder level?

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• Best practice? iphone: sync data

  - by Andy Jacobs

  So i'm working on a project where there is data visualization. My ultimate goal is that i have a set of data shipped with the download of the iphone app. But i want it connected to a backend, that if the iphone has a connection with the internet. it can sync the changes from the backend. The syncing is no problem or the connection between the backend & the iphone. But what should i use as data storage on my iphone? what is the best way. my data is purely text and doesn't have to be secure. But it's main feature should be updating certain parts of data ( adding and deleting are not so important ) so what is the easiest (read: least time consuming development ) or the best way? sqlite? plist? ..?

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• GAE modeling relationship options

  - by Sway

  Hi there, I need to model the following situation and I can't seem to find a consistent example on how to do it "correctly" for the google app engine. Suppose I've got a simple situation like the following: [Company] 1 ----- M [Stare] A company has one to many stores. Each store has an address made up of a address line 1, city, state, country, postcode etc. Ok. Lets say we need to create say an "Audit". An Audit is for a company and can be across one to many stares. So something like: [Audit] 1 ------ 1 [Company] 1 ------ M [Store] Now we need to query all of the "audits" based on the Store "addresses" in order to send the "Auditors" to the right locations. There seem to be numerous articles like this one: http://code.google.com/appengine/articles/modeling.html Which give examples of creating a "ContactCompany" model class. However they also say that you should use this kind of relationship only when you "really need to" and with "care" for performance. I've also read - frequently - that you should denormalize as much as possible thereby moving all of the "query-able" data into the Audit class. So what would you suggest as the best way to solve this? I've seen that there is an Expando class but I'm not sure if that is the "best" option for this. Any help or thoughts on this would be totally appreciated. Thanks in advance, Matt

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• What is the difference Between .erb , .rhtml and .html.erb ?

  - by sameera207

  Hi All, What is the difference Between .erb , .rhtml and .html.erb Which is recomanded thanks cheers sameera

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• In Ruby, how to implement global behaviour?

  - by Gordon McAllister

  Hi all, I want to implement the concept of a Workspace. This is a global concept - all other code will interact with one instance of this Workspace. The Workspace will be responsible for maintaining the current system state (i.e. interacting with the system model, persisting the system state etc) So what's the best design strategy for my Workspace, bearing in mind this will have to be testable (using RSpec now, but happy to look at alternatives). Having read thru some open source projects out there and I've seen 3 strategies. None of which I can identify as "the best practice". They are: Include the singleton class. But how testable is this? Will the global state of Workspace change between tests? Implemented all behaviour as class methods. Again how do you test this? Implemented all behaviour as module methods. Not sure about this one at all! Which is best? Or is there another way? Thanks, Gordon

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• Normalize or Denormalize in high traffic websites

  - by Inam Jameel

  what is the best practice for database design for high traffic websites like this one stackoverflow? should one must use normalize database for record keeping or normalized technique or combination of both? is it sensible to design normalize database as main database for record keeping to reduce redundancy and at the same time maintain another denormalized form of database for fast searching? or main database should be denormalize and one can make normalized views in the application level for fast database operations? or beside above mentioned approach? what is the best practice of designing high traffic websites???

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• Is JavaScript 's "new" Keyword Considered Harmful?

  - by Pablo Fernandez

  In another question, a user pointed out that the new keyword was dangerous to use and proposed a solution to object creation that did not use new... I didn't believe that was true, mostly because I've used Prototype, Scriptaculous and other excellent JavaScript libraries, and everyone of them used the new keyword... In spite of that, yesterday I was watching Douglas Crockford's talk at YUI theater and he said the exactly same thing, that he didn't use the new keyword anymore in his code. Is it 'bad' to use the new keyword? what are the advantages and disadvantages of using it?

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• Programming tips for writing document editors?

  - by Tesserex

  I'm asking this because I'm in the process of writing two such editors for my Mega Man engine, one a tileset editor, and another a level editor. When I say document editor, I mean the superset application type for things like image editors and text editors. All of these share things like toolbars, menu options, and in the case of image editors, and my apps, tool panes. We all know there's tons of advice out there for interface design in these apps, but I'm wondering about programming advice. Specifically, I'm doubting my code designs with the following things: Many menu options toggle various behaviors. What's the proper way to reliably tie the checked state of the option with the status of the behavior? Sometimes it's more complicated, like options being disabled when there's no document loaded. More and more consensus seems to be against using MDI, but how should I control tool panes? For example, I can't figure out how to get the panels to minimize and maximize along with the main window, like Photoshop does. When tool panels are responsible for a particular part of the document, who actually owns that thing? The main window, or the panel class? How do you do communication between the tool panels and the main window? Currently mine is all event based but it seems like there could be a better way. This seems to be a common class of gui application, but I've never seen specific pointers on code design for them. Could you please offer whatever advice or experience you have for writing them?

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• Including libraries in project. Best practise.

  - by mridang

  Hi guys, I'm writing a Python open-source app. My app uses some open source Python libraries. These libraries in turn use other open-source libraries. I intend to release my code at Sourceforge or Google Code but do I need to include the sources of the other libraries? Is this a good practice? ...or should I simply write this information into a README file informing the use about the other required libraries. I've placed all these libraries into a libs sub folder in my source directory. When checking my code into SVN, should I use something called svn:externals to link to other sources? Is there a way to dynamically update my libraries to the latest version or is this something I have to do manually when I release a new version. My sincerest apologies if my question sounds vague but I'm pretty lost in this matter and I don't know what to Google for. Thanks all.

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• Rails: find by day of week with timestamp

  - by Sleepycat

  I need to grab the records for same day of the week for the preceeding X days of the week. There must be a better way to do it than this: Transaction.find_by_sql "select * from transactions where EXTRACT(DOW from date) = 1 and organisation_id = 4 order by date desc limit 7" It gets me what I need but is Postgres specific and not very "Rails-y". Date is a timestamp. Anyone got suggestions?

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• Program Structure Design Tools? (Top Down Design)

  - by Lee Olayvar

  I have been looking to expand my methodologies to better involve Unit testing, and i stumbled upon Behavioral Driven Design (Namely Cucumber, and a few others). I am quite intrigued by the concept as i have never been able to properly design top down, only because keeping track of the design gets lost without a decent way to record it. So on that note, in a mostly language agnostic way, are there any useful tools out there i am (probably) unaware of? Eg, i have often been tempted to try building flow charts for my programs, but i am not sure how much that will help, and it seems a bit confusing to me how i could make a complex enough flow chart to handle the logic of a full program, and all its features.. ie, it just seems like flow charts would be limiting in the design scheme.. or possibly grow to an unmaintainable scale. BDD methods are nice, but with a system that is so tied to structure, tying into the language and unit testing seems like a must (for it to be worth it) and it seems to be hard to find something to work well with both Python and Java (my two main languages). So anyway.. on that note, any comments are much appreciated. I have searched around on here and it seems like top down design is a well discussed topic, but i haven't seen too much reference to tools themselves, eg, flow chart programs, etc. I am on Linux, if it matters (in the case of programs).

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• Factory Pattern - when do you say you need a specialised factory

  - by dbones

  Hi, I am having a little design crisis, I am making a Plane class, which is made of an engine 2 wings and N seats The engine takes in a engine size, and the wings have a span. would this still be feasible to have a PlaneFactory, when the factory may have to take in multiple parameters to setup the plane (wings, engine, no of seats) thanks in advance bones

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• How-to limit feature functionality

  - by ph0enix

  Are there any standard or "best practice" ways of limiting feature functionality for a particular application? Example: We have a product with a variety of features, and our customers can pick and choose which features they would like to use, and the cost of the product varies based on which features they are actually using. In the past, we have distributed along with our software installer an encrypted license file that contains information about the customer, as well as the collection of features that they have enabled. In code, we read from the license file and enable the functionality according to the license file. This seems to work fine, except there a few disadvantages: Upgrading users with new functionality can be sort of a pain If a particular feature shows up in multiple places throughout the application, a developer might not realize that this feature should be licensed, and forget to check the license file before granting functionality to the user If the license file becomes corrupted, deleted, moved, renamed, etc. the application will not run We're getting ready to roll out a new set of features, and I was just curious what others in the community have done to tackle this problem?

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