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  • general learning methodology

    - by momo
    just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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  • Java semaphore to syncronize printing to screen

    - by Travis Griswald
    I'm currently stuck on a bit of homework and was wondering if anyone could help - I have to use semaphores in java to syncronize printing letters from 2 threads - one printing "A" and one printing "B". I cannot print out more than 2 of the same character in a row, so output should look like AABABABABABBABABABABAABBAABBABABA At the moment I have 3 semaphores, a binary mutex set to 1, and a counting semaphore, and my thread classes look something like this - public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printB.up(); } } } public String produce() { printCount++; return "A"; } public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printA.up(); } } } public String produce() { printCount++; return "B"; } Yet whatever I try it either deadlocks, or it seems to be working only printing 2 in a row at most, but always seems to print 3 in a row every now and again! Any help is much appreciated, not looking code or anything just a few pointers if possible :)

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  • Use .bat file to recursively loop through folders and get hold of .class files

    - by user320550
    HI all, This is what i'm trying to do. I have a .bat file which takes in a argument which is nothing but a folder name. What i do first is go one level up (cd ..). Now in this directory i have 3 folders and each folders have sub-folders and have .class files in them. What i want to do is recursively loop through the folders and get hold of the .class files. Once this is done i want to echo the target folder of the .class file as well as echo the name of the.class file. So c:\temp\potter\myclass.class. I would echo out c:\temp\potter\ and myclass. I'm able to do this by writing a separate bat file which works. But when i integrate this with the recursive function it seems to break. This is what i'm doing: :: call the junit classes... and save the results echo step 3... cd %1 cd .. for /r %%a in (*.class) do set Var=%%a echo Full file location %Var% for %%i in ("%Var%") do Set CF=%%~dpi Set CF=%CF:~0,-1% :LOOP If "%CF:~-1,1%"=="\" GoTo :DONE Set CF=%CF:~0,-1% GoTo :LOOP :DONE Set CF=%CF:~0,-1% echo Folder Location %CF% ::cd %CF% For %%j in ("%Var%") Do Set name=%%~nxj :: -6 because of Quotations Set name=%name:~0,-6% echo File Name %name% echo step 3 complete... However i only get the output of one directory, while i have multiple directories having .class files. This is the output i get: step 3... Full file location C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCasesConve rted2JUnit\iexplore\flow2\testCase_app2.class Folder Location C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCasesConverte d2JUnit\iexplore\flow2 File Name testCase_app2 step 3 complete... missing argument! usage htmltestCaseLocation for eg., "C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCases" Could anyone please let me know whats wrong here? Thanks.

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  • C/C++ Control Structure Limitations?

    - by STingRaySC
    I have heard of a limitation in VC++ (not sure which version) on the number of nested if statements (somewhere in the ballpark of 300). The code was of the form: if (a) ... else if (b) ... else if (c) ... ... I was surprised to find out there is a limit to this sort of thing, and that the limit is so small. I'm not looking for comments about coding practice and why to avoid this sort of thing altogether. Here's a list of things that I'd imagine could have some limitation: Number of functions in a scope (global, class, or namespace). Number of expressions in a single statement (e.g., compound conditionals). Number of cases in a switch. Number of parameters to a function. Number of classes in a single hierarchy (either inheritance or containment). What other control structures/language features have limits such as this? Do the language standards say anything about these limits (perhaps minimum requirements for an implementation)? Has anyone run into a particular language limitation like this with a particular compiler/implementation? EDIT: Please note that the above form of if statements is indeed "nested." It is equivalent to: if (a) { //... } else { if (b) { //... } else { if (c) { //... } else { //... } } }

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  • Resolve php "deadlock"

    - by Matt
    Hey all, I'm currently running into a situation that I guess would be called deadlock. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php Dispatcher.php <? class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } ?> It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. Any help would be immensely helpful.. Thanks! Matt Mueller

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  • how to implement a sparse_vector class

    - by Neil G
    I am implementing a templated sparse_vector class. It's like a vector, but it only stores elements that are different from their default constructed value. So, sparse_vector would store the index-value pairs for all indices whose value is not T(). I am basing my implementation on existing sparse vectors in numeric libraries-- though mine will handle non-numeric types T as well. I looked at boost::numeric::ublas::coordinate_vector and eigen::SparseVector. Both store: size_t* indices_; // a dynamic array T* values_; // a dynamic array int size_; int capacity_; Why don't they simply use vector<pair<size_t, T>> data_; My main question is what are the pros and cons of both systems, and which is ultimately better? The vector of pairs manages size_ and capacity_ for you, and simplifies the accompanying iterator classes; it also has one memory block instead of two, so it incurs half the reallocations, and might have better locality of reference. The other solution might search more quickly since the cache lines fill up with only index data during a search. There might also be some alignment advantages if T is an 8-byte type? It seems to me that vector of pairs is the better solution, yet both containers chose the other solution. Why?

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  • Which is the better C# class design for dealing with read+write versus readonly

    - by DanM
    I'm contemplating two different class designs for handling a situation where some repositories are read-only while others are read-write. (I don't foresee any need to a write-only repository.) Class Design 1 -- provide all functionality in a base class, then expose applicable functionality publicly in sub classes public abstract class RepositoryBase { protected virtual void SelectBase() { // implementation... } protected virtual void InsertBase() { // implementation... } protected virtual void UpdateBase() { // implementation... } protected virtual void DeleteBase() { // implementation... } } public class ReadOnlyRepository : RepositoryBase { public void Select() { SelectBase(); } } public class ReadWriteRepository : RepositoryBase { public void Select() { SelectBase(); } public void Insert() { InsertBase(); } public void Update() { UpdateBase(); } public void Delete() { DeleteBase(); } } Class Design 2 - read-write class inherits from read-only class public class ReadOnlyRepository { public void Select() { // implementation... } } public class ReadWriteRepository : ReadOnlyRepository { public void Insert() { // implementation... } public void Update() { // implementation... } public void Delete() { // implementation... } } Is one of these designs clearly stronger than the other? If so, which one and why? P.S. If this sounds like a homework question, it's not, but feel free to use it as one if you want :)

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  • OO vs Simplicity when it comes to user interaction

    - by Oetzi
    Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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  • Is it possible to use SqlGeography with Linq to Sql?

    - by cofiem
    I've been having quite a few problems trying to use Microsoft.SqlServer.Types.SqlGeography. I know full well that support for this in Ling to Sql is not great. I've tried numerous ways, beginning with what would the expected way (Database type of geography, CLR type of SqlGeography). This produces the NotSupportedException, which is widely discussed via blogs. I've then gone down the path of treating the geography column as a varbinary(max), as geography is a UDT stored as binary. This seems to work fine (with some binary reading and writing extension methods). However, I'm now running into a rather obscure issue, which does not seem to have happened to many other people. System.InvalidCastException: Unable to cast object of type 'Microsoft.SqlServer.Types.SqlGeography' to type 'System.Byte[]'. This error is thrown from an ObjectMaterializer when iterating through a query. It seems to only occur when the tables containing geography columns are included in a query implicitly (ie. using the EntityRef<> properties to do joins). System.Data.Linq.SqlClient.ObjectReaderCompiler.ObjectReader`2.MoveNext() My question: If I'm retrieving the geography column as varbinary(max), I might expect the reverse error: can't cast byte[] to SqlGeography. That I would understand. This I don't. I do have some properies on the partial LINQ to SQL classes that hide the binary conversion... could those be the issue? Any help appreciated, and I know there's probably not enough information.

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  • How to model parent to child pair in MySQL (SQL)

    - by mikeschuld
    I have a data model that includes element types Stage, Actor, and Form. Logically, Stages can be assigned pairs of ( Form <--- Actor ) which can be duplicated many times (i.e. same person and same form added to the same stage at a later date/time). Right now I am modeling this with these tables: Stage Form Actor Form_Actor _______________ |Id | |FormId | --> Id in Form |ActorId | --> Id in Actor Stage_FormActor __________________ |Id | |StageId | --> Id in Stage |FormActorId | --> Id in Form_Actor I am using CodeSmith to generate the data layer for this setup and none of the templates really know how to handle this type of relationship correctly when generating classes. Ideally, the ORM would have Stage.FormActors where FormActor would be the pair Form, Actor. Is this the correct way to model these relationships. I have tried using all three Ids in one table as well Stage_Form_Actor ______________ |Id | |StageId | --> Id in Stage |FormId | --> Id in Form |ActorId | --> Id in Actor This doesn't really get generated very well either. Ideas?

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  • Write a program which works out which is the lowest priced computer in an ArrayList of computer obje

    - by Eoin
    Hello everybody! I am trying to study some java and cannot get my head around this question! Any help would be really appreciated and would help me in further studies! Thank you so much in advance! Eoin from Dublin, Ireland. ArrayList of Objects Write a program which works out which is the lowest priced computer in an ArrayList of computer objects. You should have two classes, one called ComputerTest, and the other called Computer. In the ComputerTest class you should: Have a main method which declares an ArrayList of type Computer called computerList, each element of which represents a computer. Initialise the first three entries of the ArrayList Call a static method which prints out the lowest price computer, called lowestPrice The parameter of this method is (i) an ArrayList of type Computer i.e. ArrayList data Sample output: The lowest priced computer is the Cheapo400 at 399 euro. The Computer class should have: Private instance variables: manufacturer, model, price and quality. Quality is a rating from 1 to 10. public get and set methods to retrieve and set/change the value of the four instance variables a default constructor a constructor that takes four parameters

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  • How can I get all content within <td> tag using a HTML Agility Pack?

    - by Bob Dylan
    So I'm writing an application that will do a little screen scrapping. I'm using the HTML Agility Pack to load an entire HTML page into an instance of HtmlDocoument called doc. Now I want to parse that doc, looking for this: <table border="0" cellspacing="3"> <tr><td>First rows stuff</td></tr> <tr> <td> The data I want is in here <br /> and it's seperated by these annoying <br /> 's. No id's, classes, or even a single <p> tag. </p> Just a bunch of <br /> tags. </td> </tr> </table> So I just need to get the data within the 2nd row. How can I do this? Should I use a regex or something else?

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  • How does the PHP IteratorIterator class work?

    - by WilliamMartin
    Try as I might I cannot get my head around what the IteratorIterator class actually does. I understand that classes can implement Traversable so the engine knows it can loop using foreach and I realise that IteratorIterator is supposed to convert anything that is Traversable into an Iterator but I cannot for the life of me understand how. Take for example, the PDOStatement class; how would the standard Iterator methods (next, key, rewind, etc) be implemented to allow iteration over a PDOStatement? Sorry if my question is unclear, I am just struggling to grasp the exact reason for this class and the documentation on it is scant. Thanks, Will Update: Going through the phpt files, I found one test which uses IteratorIterator: <?php $root = simplexml_load_string('<?xml version="1.0"?> <root> <child>Hello</child> <child>World</child> </root> '); foreach (new IteratorIterator($root->child) as $child) { echo $child."\n"; } ?> The expected output is: Hello World I don't really follow how the IteratorIterator construct takes $root-child as an argument and how it manages to iterate over the child elements.

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  • How do I POST/GET from rails to API with either ActiveResource or rest-client (preferred)?

    - by Angela
    Hi, this is a pretty basic question but I'm not entirely clear how to do this. I am trying to use a third-party service that has RESTful service. The service is called Postful. But I'm not clear what exactly to do? I've looked at ActiveResource (http://api.rubyonrails.org/classes/ActiveResource/Base.html) and rest-client, but I'm still not clear exactly what steps, code, and files to create. http://www.postful.com/service/mail is one of the services (details found http://www.postful.com/developer/guide#rest ), but to upload an image I have to post the following (but I'm not sure how I actually do this?). Thanks! > http://www.postful.com/service/upload > > Be sure to include the Content-Type > and Content-Length headers and the > image itself as the body of the > request. > > POST /upload HTTP/1.0 Content-Type: > application/octet-stream > Content-Length: 301456 > > ... file content here ... > > If the upload is successful, you will > receive a response like the following: > > <?xml version="1.0" encoding="UTF-8"?> > <upload> > <id>290797321.waltershandy.2</id> > </upload>

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  • Resolve php endless recursion issue

    - by Matt
    Hey all, I'm currently running into an endless recursion situation. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. I'm looking for some kind of queue implementation that will make messages wait for each other.. One where the return values still get set. I'm looking to have as little boilerplate code in class A and class B as possible Any help would be immensely helpful.. Thanks! Matt Mueller

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  • C# Hiding, overriding and calling function from base class.

    - by Lukasz Lysik
    I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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  • Rails: Getting rid of "X is invalid" validation errors

    - by DJTripleThreat
    I have a sign-up form that has nested associations/attributes whatever you want to call them. My Hierarchy is this: class User < ActiveRecord::Base acts_as_authentic belongs_to :user_role, :polymorphic => true end class Customer < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end class Employee < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end I have some validation stuff in these classes as well. My problem is that if I try to create and Customer (or Employee etc) with a blank form I get all of the validation errors I should get plus some Generic ones like "User is invalid" and "Customer is invalid" If I iterate through the errors I get something like: user.login can't be blank User is invalid customer.whatever is blah blah blah...etc customer.some_other_error etc etc Since there is at least one invalid field in the nested User model, an extra "X is invalid" message is added to the list of errors. This gets confusing to my client and so I'm wondering if there is a quick way to do this instead of having to filer through the errors myself.

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  • Passing Derived Class Instances as void* to Generic Callbacks in C++

    - by Matthew Iselin
    This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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  • New Rails deployment half working...not sure why?

    - by Meltemi
    I'm in the final stages of going round trip through the entire Rails cycle: development - test - production (on an external server). I'm very close...but seeing some errors with the production version and don't know enough about Rails' "magic" to troubleshoot it yet... all seems well and I can load my app by going to www.mydomain.com/rails and it seems to work...I can interact with my app and create new objects in my database. However, when I go to www.mydomain.com/rails/ (difference is the trailing slash) i get a webpage that just says "Index from public" on it?!? I don't know where that's coming from? index.html is long removed from public. this may or may not be related to why I can't access, say, the first record in one of my classes by calling its controller like so: www.mydomain.com/rails/mycontroller/1 . and yes, there are records in the database. anyway, something's askew. it works fine on development box. but, only half working on production server. anyone know what might be causing this? this app is running on the server box (not development) Installed Passenger on server to serve app via Apache modified my httpd.conf with Passenger's stuff (headache but finally got it to respond) loaded schema into the production database: rake db:schema:load RAILS_ENV=production

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  • Fluent NHibernate Map to private/protected Field that has no exposing Property

    - by Jon Erickson
    I have the following Person and Gender classes (I don't really, but the example is simplified to get my point across), using NHibernate (Fluent NHibernate) I want to map the Database Column "GenderId" [INT] value to the protected int _genderId field in my Person class. How do I do this? FYI, the mappings and the domain objects are in separate assemblies. public class Person : Entity { protected int _genderId; public virtual int Id { get; private set; } public virtual string Name { get; private set; } public virtual Gender Gender { get { return Gender.FromId(_genderId); } } } public class Gender : EnumerationBase<Gender> { public static Gender Male = new Gender(1, "Male"); public static Gender Female = new Gender(2, "Female"); private static readonly Gender[] _genders = new[] { Male, Female }; private Gender(int id, string name) { Id = id; Name = name; } public int Id { get; private set; } public string Name { get; private set; } public static Gender FromId(int id) { return _genders.Where(x => x.Id == id).SingleOrDefault(); } }

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  • Have I found a security problem in an API or do I just not understand SSL?

    - by jamieb
    I'm working on building a set of Python bindings around an XML-based API provided by a vendor. The vendor requires that all transactions be conducted over SSL. Using a Linux box, I created a key file and a CSR for my application. Using their self-service web portal, I then generate a certificate using that CSR. Both the key file and the certificate are used when making the SSL request to the API. I'm now working on designing exception classes to make error messages more verbose (and, hopefully, more useful to developers using my bindings). Part of my testing has included altering the key file: transpose a couple characters here, replace 4 or 5 with random characters there, etc. To my surprise, altering the key file had no effect! As long as I didn't change the total length of it, the API didn't complain about a bad key file. The only way I was able to throw an error was by swapping in a completely different key from another application. At that point, the API complained about the Common Name not matching. Is this normal behavior or has the vendor not properly implemented SSL?

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  • Should a setter return immediately if assigned the same value?

    - by Andrei Rinea
    In classes that implement INotifyPropertyChanged I often see this pattern : public string FirstName { get { return _customer.FirstName; } set { if (value == _customer.FirstName) return; _customer.FirstName = value; base.OnPropertyChanged("FirstName"); } } Precisely the lines if (value == _customer.FirstName) return; are bothering me. I've often did this but I am not that sure it's needed nor good. After all if a caller assigns the very same value I don't want to reassign the field and, especially, notify my subscribers that the property has changed when, semantically it didn't. Except saving some CPU/RAM/etc by freeing the UI from updating something that will probably look the same on the screen/whatever_medium what do we obtain? Could some people force a refresh by reassigning the same value on a property (NOT THAT THIS WOULD BE A GOOD PRACTICE HOWEVER)? 1. Should we do it or shouldn't we? 2. Why?

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  • Database nesting layout confusion

    - by arzon
    I'm no expert in databases and a beginner in Rails, so here goes something which kinda confuses me... Assuming I have three classes as a sample (note that no effort has been made to address any possible Rails reserved words issue in the sample). class File < ActiveRecord::Base has_many :records, :dependent => :destroy accepts_nested_attributes_for :records, :allow_destroy => true end class Record < ActiveRecord::Base belongs_to :file has_many :users, :dependent => :destroy accepts_nested_attributes_for :users, :allow_destroy => true end class User < ActiveRecord::Base belongs_to :record end Upon entering records, the database contents will appear as such. My issue is that if there are a lot of Files for the same Record, there will be duplicate record names. This will also be true if there will be multiple Records for the same user in the the Users table. I was wondering if there is a better way than this so as to have one or more files point to a single Record entry and one or more Records will point to a single User. BTW, the File names are unique. Files table: id name 1 name1 2 name2 3 name3 4 name4 Records table: id file_id record_name record_type 1 1 ForDaisy1 ... 2 2 ForDonald1 ... 3 3 ForDonald2 ... 4 4 ForDaisy1 ... Users table: id record_id username 1 1 Daisy 2 2 Donald 3 3 Donald 4 4 Daisy Is there any way to optimize the database to prevent duplication of entries, or this should really the correct and proper behavior. I spread out the database into different tables to be able to easily add new columns in the future.

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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • Google Spreadsheet API problem: memory exceeded

    - by Robbert
    Hi guys, Don't know if anyone has experience with the Google Spreadsheets API or the Zend_GData classes but it's worth a go: When I try to insert a value in a 750 row spreadsheet, it takes ages and then throws an error that my memory limit (which is 128 MB!) was exceeded. I also got this when querying all records of this spreadsheet but this I can imaging because it's quite a lot of data. But why does this happen when inserting a row? That's not too complex, is it? Here's the code I used: public function insertIntoSpreadsheet($username, $password, $spreadSheetId, $data = array()) { $service = Zend_Gdata_Spreadsheets::AUTH_SERVICE_NAME; $client = Zend_Gdata_ClientLogin::getHttpClient($username, $password, $service); $client->setConfig(array( 'timeout' => 240 )); $service = new Zend_Gdata_Spreadsheets($client); if (count($data) == 0) { die("No valid data"); } try { $newEntry = $service->insertRow($data, $spreadSheetId); return true; } catch (Exception $e) { return false; } }

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