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Search found 650 results on 26 pages for 'flaws and pitfalls'.

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  • Python 3: timestamp to datetime: where does this additional hour come from?

    - by Beau Martínez
    I'm using the following functions: # The epoch used in the datetime API. EPOCH = datetime.datetime.fromtimestamp(0) def timedelta_to_seconds(delta): seconds = (delta.microseconds * 1e6) + delta.seconds + (delta.days * 86400) seconds = abs(seconds) return seconds def datetime_to_timestamp(date, epoch=EPOCH): # Ensure we deal with `datetime`s. date = datetime.datetime.fromordinal(date.toordinal()) epoch = datetime.datetime.fromordinal(epoch.toordinal()) timedelta = date - epoch timestamp = timedelta_to_seconds(timedelta) return timestamp def timestamp_to_datetime(timestamp, epoch=EPOCH): # Ensure we deal with a `datetime`. epoch = datetime.datetime.fromordinal(epoch.toordinal()) epoch_difference = timedelta_to_seconds(epoch - EPOCH) adjusted_timestamp = timestamp - epoch_difference date = datetime.datetime.fromtimestamp(adjusted_timestamp) return date And using them with the passed code: twenty = datetime.datetime(2010, 4, 4) print(twenty) print(datetime_to_timestamp(twenty)) print(timestamp_to_datetime(datetime_to_timestamp(twenty))) And getting the following results: 2010-04-04 00:00:00 1270339200.0 2010-04-04 01:00:00 For some reason, I'm getting an additional hour added in the last call, despite my code having, as far as I can see, no flaws. Where is this additional hour coming from?

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  • Developing ASP.NET MVC UI Extensions - best approach

    - by user252160
    What are the best practices in developing rich UI extensions for ASP.NET MVC (I mean asynchronous / partial loading, slick effects, skinning etc) ? I saw that Telerik has an MVC suite of extensions, but haven't tried them yet, so I cannot comment on them. My biggest concern as of the moment is how to structure the code of my extensions so that C#, ASP markup, and JQuery remain separate from each other, yet encapsulated in a way that the extension must be easy to distribute and reuse. I know that the user control approach had many flaws, yet it sort of allowed application developers to just reference a control, set some parameters and get it going in a few minutes. I'd like to achieve the same kind of portability/reusability as I still keep the code easy to extend and build upon. Now, some ideas that come to mind as topics for discussion are: template helpers vs. extension method helpers or a possible integration efficient use of jQuery - naming conventions - - asynchronous action loading - etc you can add whatever comes to your mind

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  • Boost Thread Specific Storage Question (boost/thread/tss.hpp)

    - by Hassan Syed
    The boost threading library has an abstraction for thread specific (local) storage. I have skimmed over the source code and it seems that the TSS functionality can be used in an application with any existing thread regardless of weather it was created from boost::thread --i.e., this implies that certain callbacks are registered with the kernel to hook in a callback function that may call the destructor of any TSS objects when the thread or process is going out of scope. I have found these callbacks. I need to cache HMAC_CTX's from OpenSSL inside the worker threads of various web-servers (see this, detailed, question for what I am trying to do), and as such I do not controll the life-time of the thread -- the web-server does. Therefore I will use the TSS functionality on threads not created by boost::thread. I just wanted to validate my assumptions before I started implementing the caching logic, are there any flaws in my logic ?

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  • OOP Design for an Economy

    - by waiwai933
    Not sure where to start, so I'm just going to plow in. Let's say I'm trying to represent an economy in OOP. A basic design I've come up with is: class Person{ int $money; // Money someone has in wallet/purse int $bank_account_id; function getAmountOfMoney() function addMoney($amountToAdd) function subtractMoney($amountToSubtract) } class BankAccount{ int $money; // Money in Bank Account int $interest_per_year; function giveInterest() function depositMoney() // Calls $person->subtractMoney() function withdrawMoney() // Calls $person->addMoney() } Are there any design flaws here?

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  • Using Subversion in Xcode

    - by Kevin L.
    It seems that all of the initial Google results for "using subversion with xcode" are actually just tutorials for installing and configuring svn and Xcode, as opposed to actually using the two (i.e. interacting with svn via Xcode's GUI). Is anyone aware of a good guide that teaches the tricks and pitfalls of working with svn via Xcode's GUI? Something that bridges the gap between the most excellent Version Control with Subversion book and the Xcode IDE (as in pure Xcode GUI without any terminal command use)? Edit: We all love our terminal commands, and we all love Eclipse but (and I mean this in the nicest possible way) neither is really the point of the question. I’d prefer to use svn via Xcode’s IDE instead of via terminal just as I prefer (well, for this case) to code in Xcode’s IDE instead of using vim and gcc. Apple engineers spent a good bit of time implementing that SCM menu in Xcode; someone has to have seen a usage guide somewhere.

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  • Subclassing UIScrollView for drawing w/o views

    - by David Dunham
    I'm contemplating subclassing UIScrollView (the way UITextView does) to draw a fairly large amount of text (formatted in ways that NSTextView can't). So far the view won't actually scroll. I'm setting contentSize, and when I drag, I see the scroll indicator. But nothing changes (and I don't get a drawRect: message). An alternate approach is to use a child view, and I've done this. The view can be over 5000 pixels high, however, and I'm a bit concerned about performance on an actual device. (The other approach, be like UITableView, would be a huge pain -- I'm "porting" Mac Cocoa code, and a collection of views would be a huge architecture change.) I've done some searching, but haven't found anyone who is using UIScrollView to do the drawing. Has anyone done this and know of any pitfalls?

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  • Declarative authorization and the if_attribute not working...

    - by ro
    I've been having almost the same issues as Victor Martin (you can see the questions asked here). I've got declarative authorization working for just about everything that doesn't involve using conditionals. E.g. has_permission_on :users, :to => [:edit, :update, :destroy] do if_attribute :user => is { current_user } end Are there any common pitfalls with Declarative Authorization? I'm using authlogic and I'm suspicious the 'current_user' method in the application controller might be the source of the problem.

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  • Differences Between Java and HTML5 -- Squeezed Background

    - by ashes999
    I noticed some (slightly disturbing) differences between the HTML5 and the Java versions of the playN showcase (source). (I just downloaded everything yesterday, so presumably I'm running the latest samples.) Specifically, two flaws I noticed in the HTML5 version: The text on the buttons is quite blurry (not anti-aliased, but actually blurry) compared to the Java version The background in the "Swirl" sample is restricted to one corner of the app; it doesn't cover the entire visible space the way it does in the Java version. Are these bugs, or the expected behaviour?

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  • Is wordpress a good platform for webapp development?

    - by darlinton
    I am planning a webapp to control bank paying orders. In a quick review, the user goes online and creates a payment order. This order goes to other people that pays it and register the payment on the system. The system keeps track of all the payments, keeping the account balance up-to-date. The system needs a login system, bank integration, and to support at some point thousands of clients. We can find articles on the web about the benefits of using wordpress platform to build webapps. However, I could not find discussion with counterarguments to user wordpress. As the platform the most important choice in webapp project, I would to know more about the pitfalls and harms for choosing wordpress. The question is: What are the benefits and harms for choosing wordpress as a development platform for a webapp that need to be integrated with other system (backend systems) and to handle thousands of users (does it scale up?)?

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  • Common programming mistakes for Scala developers to avoid

    - by jelovirt
    In the spirit of Common programming mistakes for Java developers to avoid? Common programming mistakes for JavaScript developers to avoid? Common programming mistakes for .NET developers to avoid? Common programming mistakes for Haskell developers to avoid? Common programming mistakes for Python developers to avoid? Common Programming Mistakes for Ruby Developers to Avoid Common programming mistakes for PHP developers to avoid? what are some common mistakes made by Scala developers, and how can we avoid them? Also, as the biggest group of new Scala developers come from Java, what specific pitfalls they have to be aware of? For example, one often cited problem Java programmers moving to Scala make is use a procedural approach when a functional one would be more suitable in Scala. What other mistakes e.g. in API design newcomers should try to avoid.

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  • Programming user interface advice?

    - by onurozcelik
    Hi, In my project I going to generate a user interface through programming. Scalability of this UI is very important requirement. So far I am using two dimensional graphics for generating the UI. I think there may be different solutions but for the moment I know only two. First one is supplying X,Y coordinates of each two dimensional graphic on my UI.(I do not prefer this solution because I do not want to calculate X,Y coordinates of each graphic. For the moment I don't have a logic for doing this easily) Second one(which is currently I am using now) is using layouts which organizes its contents according to size of item. In this solution I don't have to calculate X,Y coordinates of each item.(Layout is doing this for me) But this approach may have its own pitfalls. I am very new to user interface programming. Can you give me advice about this issue?

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  • Multiple merchant accounts with Activemerchant gem.

    - by sosborn
    I am developing a rails site that will allow a group of merchants (5 - 10) to accept credit card orders online. I plan on using the Activemerchant gem to handle the processing. In this case, each merchant will have their own merchant accounts to handle the payments. Storing banking information like that is not something I am a fan of. This could be solved by queing orders and allowing the merchant to log in to the site, input their credentials and process the order. However, if I go that route then it seems to me that I would have to store the customers' credit card information temporarily until the merchant has the opportunity to log in and process the order, which to me is the greater evil. Has anyone dealt with this situation? If so, what are the options available and what pitfalls should I look out for? In my mind, security customer credit card information is priority number one with the merchant account information a close second.

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  • Rails - Associations - Automatically setting an association_id for a model which has 2 belongs_to

    - by adam
    I have 3 models class User < ... belongs_to :language has_many :posts end class Post < ... belongs_to :user belongs_to :language end class Language < ... has_many :users has_many :posts end Im going to be creating lots of posts via users and at the same time I have to also specify the language the post was written in, which is always the language associatd with the user i.e. @user.posts.create(:text => "blah", :language_id => @user.language_id) That's fine but the way I set the language doesn't sit well with me. The language will always be that of the users so is there a 'best-practice' way of doing this? I know a little about callbacks and association extensions but not sure of any pitfalls.

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  • Do I need to auto-login after account activation?

    - by Art
    This is the standard scenario: User registers on the site User receives an account activation email, clicks link to activate Web site notifies the user that account is activated Now there are at least two pathways: User is taken to the login screen and asked to enter login details User is automatically logged in and taken to a welcome/profile/etc page While there are obvious benefits in (1) as far as the user's experience is concerned, there could be drawbacks as well. Option (2) offers improved security at cost of UX. Which of the scenarios is preferable and why? Any serious flaws in any of them?

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  • Reading data from a socket, considerations for robustness and security

    - by w.brian
    I am writing a socket server that will implement small portions of the HTTP and the WebSocket protocol, and I'm wondering what I need to take into consideration in order to make it robust/secure. This is my first time writing a socket-based application so please excuse me if any of my questions are particularly naive. Here goes: Is it wrong to assume that you've received an entire HTTP request (WebSocket request, etc) if you've read all data available from the socket? Likewise, is it wrong to assume you've only received one request? Is TCP responsible for making sure I'm getting the "message" all at once as sent by the client? Or do I have to manually detect the beginning and end of each "message" for whatever protocol I'm implementing? Regarding security: What, in general, should I be aware of? Are there any common pitfalls when implementing something like this? As always, any feedback is greatly appreciated.

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  • Is there a standard practice for synchronizing SQL Server tables?

    - by EngineeringAutomation
    I've written an application that retrieves pricing and part options from a SQL database to generate a 3D Model of the product and create a sales proposal. My client likes it so much they want to be able to use it on laptops in the field now. The catch is, they won't have an internet connection. I'm considering setting up a SQLite database as part of the standard installation. The SQLite database on each laptop will synchronize with the main database when the internet connection is re-established. Are there best practices regarding synchronizing SQL tables like this? Are there any pitfalls I should consider? I'm open to all options. Thank you.

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  • What are some of best Javascript memory detecting tools?

    - by Philip Fourie
    Our team is faced with slow but serious Javascript memory leak. We have read up on the normal causes for memory leaks in Javascript (eg. closures and circular references). We tried to avoid those pitfalls in the code but it likely we still have unknown mistakes left in our code. I started my search for available tools but would like input from people with actual experience with these tools. Some of the tools I found so far (but have no idea how good and useful they would be for our problem): Sieve Drip JavaScript Memory Leak Detector Our search is not limited to free tools, it will be a bonus, but more importantly something that will get the job done. We do the following in our Javascript code: AJAX calls to a .NET WCF back-end that send back JSON data Manipulate the DOM Keep a fairly sized object model in the Javascript to store current state

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  • Display message when user leaves site

    - by Brian Rasmusson
    Hi, I'm looking for a way to display a message to the user if he leaves my site after only viewing one page. I found this (http://www.pgrs.net/2008/1/30/popup-when-leaving-website) clever solution, but it has a few flaws: staying_in_site = false; Event.observe(document.body, 'click', function(event) { if (Event.element(event).tagName == 'A') { staying_in_site = true; } }); window.onunload = popup; function popup() { if(staying_in_site) { return; } alert('I see you are leaving the site'); } It displays the message also when refreshing the page or using the back button. Do you know a better solution or how to fix it in the above code? I'm no javascript master :) My intention is to add the code on very specific landing pages only, and display the message when people leave the page without downloading my trial software or reading other pages on my site.

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  • NHibernate session management in ASP.NET MVC

    - by Kevin Pang
    I am currently playing around with the HybridSessionBuilder class found on Jeffrey Palermo's blog post: http://jeffreypalermo.com/blog/use-this-nhibernate-wrapper-to-keep-your-repository-classes-simple/ Using this class, my repository looks like this: public class UserRepository : IUserRepository { private readonly ISessionBuilder _sessionBuilder; public UserRepository(ISessionBuilder sessionBuilder) { _sessionBuilder = sessionBuilder; } public User GetByID(string userID) { using (ISession session = _sessionBuilder.GetSession()) { return session.Get<User>(userID); } } } Is this the best way to go about managing the NHibernate session / factory? I've heard things about Unit of Work and creating a session per web request and flushing it at the end. From what I can tell, my current implementation isn't doing any of this. It is basically relying on the Repository to grab the session from the session factory and use it to run the queries. Are there any pitfalls to doing database access this way?

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  • How to handle an "infinite" IEnumerable?

    - by Danvil
    A trivial example of an "infinite" IEnumerable would be IEnumerable<int> Numbers() { int i=0; while(true) { yield return i++; } } I know, that foreach(int i in Numbers().Take(10)) { Console.WriteLine(i); } and var q = Numbers(); foreach(int i in q.Take(10)) { Console.WriteLine(i); } both work fine (and print out the number 0-9). But are there any pitfalls when copying or handling expressions like q? Can I rely on the fact, that they are always evaluated "lazy"? Is there any danger to produce an infinite loop?

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  • When to use POJO and When to use SLSB

    - by user83795
    we are using EJB3 in our application. Our design aim is to separate persistence layer from Business Layer. So we have developed XXXbean classes to be used as SLSB and XXXRepository classes to be used as persistence classes. We also have POJO that implement reusable NON business logic(get list of countries etc) and we call then service/helper Classes. We use EJB3 JPA (using Hibernate provider) and Repository classes has all the methods for CRUD operation and the get methods for data access. Currently XXXRepository classes are all POJO and we instantiate these classes directly from the bean XXXClasses or from the service Objects. Should the XXXRepository classes be SLSB ? what would be the benefits and pitfalls of converting them to SLSB?

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  • Password reset by email without a database table

    - by jpatokal
    The normal flow for resetting a user's password by mail is this: Generate a random string and store it in a database table Email string to user User clicks on link containing string String is validated against database; if it matches, user's pw is reset However, maintaining a table and expiring old strings etc seems like a bit of an unnecessary hassle. Are there any obvious flaws in this alternative approach? Generate a MD5 hash of the user's existing password Email hash string to user User clicks on link containing string String is validated by hashing existing pw again; if it matches, user's pw is reset Note that the user's password is already stored in a hashed and salted form, and I'm just hashing it once more to get a unique but repeatable string. And yes, there is one obvious "flaw": the reset link thus generated will not expire until the user changes their password (clicks the link). I don't really see why this would be a problem though -- if the mailbox is compromised, the user is screwed anyway.

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  • Html combo box to database record Id

    - by LanguaFlash
    I'm fairly sure there has to be a simple solution to my problem, but I am a new web developer and can't quite figure it out. On my page I have a combo box whose values are filled from my database. When the user submits the form, how to I go about converting those values back to the record numbers in the database? Up to now I have been just doing a sort of reversed lookup in my database to try to get the record's ID. This has quite a few obvious flaws and I am sure that there has to be a better way. I am used to MS Forms combo boxes where the record data and ID are never separated. But in the case of a web form, I have no way to do multiple columns in the combo box like I am used to. Thanks! Jeff

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  • .NET Framework - Possible memory-leaky classes?

    - by Robert Fraser
    Just the other day I was investigating a memory leak that was ballooning the app from ~50MB to ~130MB in under two minutes. Turns out that the problem was with the ConcurrentQueue class. Internally, the class stores a linked list of arrays. When an item is dequeued from the ConcurrentQueue, the index in the array is bumped, but the item remains in the array (i.e. it's not set to null). The entire array node is dropped after enough enqueues/dequeues, so it's not technically a leak, but if storing only a few large objects in the ConcurrentQueue, this can get out of hand fast. The documentation makes no note of this danger. I was wondering what other potential memory pitfalls are in the Base Class Library? I know about the Substring one (that is, if you call substring and just hold onto the result, the whole string will still be in memory). Any others you've encountered?

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  • Why doesn't GCC produce a warning when assigning a signed literal to an unsigned type?

    - by maerics
    Several questions on this website reveal pitfalls when mixing signed and unsigned types and most compilers seem to do a good job about generating warnings of this type. However, GCC doesn't seem to care when assigning a signed constant to an unsigned type! Consider the following program: /* foo.c */ #include <stdio.h> int main(void) { unsigned int x=20, y=-30; if (x > y) { printf("%d > %d\n", x, y); } else { printf("%d <= %d\n", x, y); } return 0; } Compilation with GCC 4.2.1 as below produces no output on the console: gcc -Werror -Wall -Wextra -pedantic foo.c -o foo The resulting executable generates the following output: $ ./foo 20 <= -30 Is there some reason that GCC doesn't generate any warning or error message when assigning the signed value -30 to the unsigned integer variable y?

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