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• What exactly does "adopt a protocol" mean in the Objective-C / Cocoa documentation ?

  - by driis

  I am a C# developer getting started on Objective-C / Cocoa Touch programming. I think I might have gotten some terms wrong because I keep thinking about them "the C# way". Specifically, I have come around the term "protocol" in various documentation and tutorials. In Objective-C, what exactly is a protocol ? Can it be compared to a C# interface ? Is the following declaration the same as saying "The class is implementing the protocol UITextFieldDelegate" ? Or is UITextFieldDelegate to be compared with a generic type parameter in C# ? @interface MyViewController : UIViewController <UITextFieldDelegate> { }

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• Better name needed for applying a function on elements of a container

  - by stefaanv

  I have a container class (containing a multi-index container) for which I have a public "foreach" member-function, so users can pass a functor to apply on all elements. While implementing, I had a case where the functor should only be applied to some elements of a range in the container, so I overloaded the foreach, to pass some valid range. Now, in some cases, it was worthwhile to stop on a certain condition, so practically, I let the foreach stop based on the return-value of the function. I'm pleased with how the system works, but I have one concern: How should a "foreach" on a range, with stop conditions be called? Anyone knows a generic, clear and concise name?

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• OpenSSL compatible API for Scala?

  - by pfleidi

  Hello, I'm working on a project with a friend. He's implementing his software in Ruby and I'm doing my stuff in Scala (with Lift). We're using some asynchronous encryption and he is using the ruby OpenSSL bindings for that: key = OpenSSL::PKey::RSA.generate(4096) self.public_key = key.public_key self.private_key = key What I'm looking for is a simple API which is compatible to OpenSSL and runs on the JVM. I need it to create key-pairs and to encrypt and sign our payload. Do you have any suggestions?

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• onbeforeunload dilemma: iframe breaking vs. annoying message on refresh/back buttons click

  - by Tossapol

  I'm implementing a search service called SearchInsideOut. http://bit.ly/97SFyW This search service simply replaces web page results by full web pages (Yes, I used iframe). The problem I have to deal with is iframe-breaking pages. The promising solution I found is using onbeforeunload to let users decide whether to stay or leave my site. But this also creates another annoying behavior. When users click other links in my site, onbeforeunload will also be triggered. Fortunately, I could solve this case by placing window.onbeforeunload=null in the onclick event of those links of my site. Unfortunately, I have no idea how to detect external events like clicking "refresh/back" buttons. What should I do to solve this difficulty? All suggestions and comments are highly appreciated.

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• How do you call a method for an Objective-C object's superclass from elsewhere?

  - by executor21

  If you're implementing a subclass, you can, within your implementation, explicitly call the superclass's method, even if you've overridden that method, i.e.: [self overriddenMethod]; //calls the subclass's method [super overriddenMethod]; //calls the superclass's method What if you want to call the superclass's method from somewhere outside the subclass's implementation, i.e.: [[object super] overriddenMethod]; //crashes Is this even possible? And by extension, is it possible to go up more than one level within the implementation, i.e.: [[super super] overriddenMethod]; //will this work?

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• Want to understand C++ sentry object

  - by Romain Hippeau

  I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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• The C vs. C++ way

  - by amc

  Hi, So I have to write a program that will iterate through an image and record the pixel locations corresponding to each color pixel that appears in it. For example, given http://www.socuteurl.com/fishywishykissy I need to find the coordinates of all yellow, purple, dark pink, etc pixels. In C++ I would use a hash table to do this. I would iterate through the image, check each pixel's value, look up that value and either add to a vector of pixel coordinates if it were found or add a new entry to the table if the value were not already there. The problem is that I may need to write this program in pure C instead of C++. How would I go about doing this in C? I feel like implementing a hash table would be pretty obnoxious and error-prone: should I avoid doing that? I'm pretty inexperienced with C and have a fair amount of C++ experience, if that matters. Thanks.

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• Use CSS selectors to collect HTML elements from a streaming parser (e.g. SAX stream)

  - by Jakub Narebski

  How to parse CSS (CSS3) selector and use it (in jQuery-like way) to collect HTML elements not from DOM (from tree structure), but from stream (e.g. SAX), i.e. using sequential access parser? Are there CSS selectors that need access to DOM (Wikipedia SAX page says that XPath selectors "need to be able to access any node at any time in the parsed XML tree")? I am most inetersted in implementing selector combinators, e.g. 'A B' descendant selector. I prefer solutions describing algorithm, or in Perl.

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• ASP.NET web services leak memory when (de)serializing disposable objects?

  - by Serilla

  In the following two cases, if Customer is disposable (implementing IDisposable), I believe it will not be disposed by ASP.NET, potentially being the cause of a memory leak: [WebMethod] public Customer FetchCustomer(int id) { return new Customer(id); } [WebMethod] public void SaveCustomer(Customer value) { // save it } This flaw applies to any IDisposable object. So returning a DataSet from a ASP.NET web service, for example, will also result in a memory leak - the DataSet will not be disposed. In my case, Customer opened a database connection which was cleaned up in Dispose - except Dispose was never called resulting in loads of unclosed database connections. I realise there a whole bunch of bad practices being followed here (its only an example anyway), but the point is that ASP.NET - the (de)serializer - is responsible for disposing these objects, so why doesn't it? This is an issue I was aware of for a while, but never got to the bottom of. I'm hoping somebody can confirm what I have found, and perhaps explain if there is a way of dealing with it.

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• StreamTokenizer Iterator Adapter help

  - by alpdog14

  I have this StreamTokenizer Iterator Adapter that is suppose to create a Tokenizer Iterator Index Builder then build the index from a STIA wrapped around a StreamTokenizer. I am having trouble implementing the hasNext and Next for my STIA, can anyone help me, here is my class: public class StreamTokenizerIteratorAdapter implements Iterator<Token> { DefaultIndexImpl index; StreamTokenizer source; public StreamTokenizerIteratorAdapter(final StreamTokenizer source) { if (source == null) throw new IllegalArgumentException("source == null"); } @Override public boolean hasNext() { return !index.isEmpty(); } public Token next() { if(!index.isEmpty()) return next(); else return null; } @Override public void remove() { throw new UnsupportedOperationException(); } } Should I be using the source element in the hasNext() and next()?

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• How would I implement separate databases for reading and writing operations?

  - by Matt

  I am interested in implementing an architecture that has two databases one for read operations and the other for writes. I have never implemented something like this and have always built single database, highly normalised systems so I am not quite sure where to begin. I have a few parts to this question. 1. What would be a good resource to find out more about this achitecture? 2. Is it just a question of replicating between two identical schemas, or would your schemas differ depending on the operations, would normalisation vary too? 3. How do you insure that data written to one database is immediately available for reading from the second? Any further help, tips, resources would be appreciated. Thanks.

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• Is it possible to avoid C++ compiler error (C2757) where 2 different header files contain same symbol for namespace & class?

  - by dharmendra

  Hi, I am facing a problem when implementing some new code to an existing library. This library already references a class with a name say 'foo'. The same name is used as a namespace in the other header file which has to be included to implement the new functionality. Since both the header files are a part of legacy code libraries I cannot amend them. So here I am looking for any way so as to avoid the Compiler Error (C2757: a symbol with this name already exists and therefore this name cannot be used as a namespace name). I am not sure whether it is possible or not. Hence, Any help shall be appreciated. Thanks For clarity here is the sample code illustration for the issue: HeaderA.h class foo {} HeaderB.h namespace foo { class ABC{} } HeaderC.h #include <HeaderA.h> #include <HeaderB.h> using namespace foo; class Toimplement{ ABC a; //Throws Error C2757 }

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• How to hash and check for equality of objects with circular references

  - by mfya

  I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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• WCF interoperability with WSDL proxy and performance consideration advise.

  - by user194917

  I'm essentially writing a broker service. The requirement is that I write an API that acts as an intermediary broker between our in-house developed services and a 3rd party provided API. The intention being that my API abstract the actual communication with the 3rd party API from our internal systems. The architect on the project chose WCF as the communication framework. The problem is that 70 percent of our subscriber applications are written in .Net 2 and as such have no access to the class libraries required to implement a WCF proxy. The end result being that our proxy classes are loosely based on the code auto generated by the WSDL tool as opposed to the SvcUtil tool. My question is, although I have no issues implementing the required proxy classes using basicHttp as the actual binding and using the WSDL tool, are there any special considerations that I need to take into account in this scenario? I.E proxy optimizations and the like. Thanks in advance.

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• BASH: Checking for environment variables

  - by Hamza

  Hi folks, I am trying to check the value of an environment variable and depending on the value do certain things and it works fine as long as the variable is set. When it isn't though I get a whole bunch of errors (as BASH is trying to compare the string I specify with an undefined variable, I guess) I tried implementing an extra check to prevent it happening but no luck. The block of code I am using is: #!/bin/bash if [ -n $TESTVAR ] then if [ $TESTVAR == "x" ] then echo "foo" exit elif [ $TESTVAR == "y" ] then echo "bar" exit else echo "baz" exit fi else echo -e "TESTVAR not set\n" fi And this the output: $ export TESTVAR=x $ ./testenv.sh foo $ export TESTVAR=y $ ./testenv.sh bar $ export TESTVAR=q $ ./testenv.sh baz $ unset TESTVAR $ ./testenv.sh ./testenv.sh: line 5: [: ==: unary operator expected ./testenv.sh: line 9: [: ==: unary operator expected baz My question is, shouldn't 'unset TESTVAR' nullify it? It doesn't seem to be the case... Thanks.

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• hook_form for multiple content types defined by the same module

  - by pao13gate

  A new module 'foo' implements foo_node_info() where one or more new content types can be defined. If foo_node_info() defines two content types, namely a content type 'footypea' and a content type 'footypeb', how does one go about implementing hook_form() (what should the name of the "hook" be?) to configure each node's editing form? In the drupal example, the name of the new content type is the same as the module name. What happens in the above described example where two new content types are defined by the module? Should the implemented hook_form() function be of the form: footypea_form() and footypeb_form() ? (this doesn't seem to work) Or should you implement a single foo_form() function and within this create and return an array $form with elements $form['footypea'] and $form['footypeb'] that are in turn arrays of the individual form field definitions?

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• Open source framework à la Microsoft Sync Framework suggestions?

  - by drskol

  We are implementing a warehouse management system atop an open source stack (Java, web services & friends). In this system, we want to integrate many mobile devices which should also be capable of adequate online/offline functionality, e.g. preparing database inserts while a mobile device is temporarily unconnected, and performing them on the backend database when reconnected. For a .NET stack, Microsoft Sync Framework would be a perfect solution, e.g. to do database replication and hoarding. Can anyone suggest an open source alternative to the MS Sync Framework and possibly describe his experiences with it? Thanks in advance for any answers.

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• User Defined Class as a Template Parameter

  - by isurulucky

  Hi, I' m implementing a custom STL map. I need to make sure that any data type (basic or user defined) key will work with it. I declared the Map class as a template which has two parameters for the key and the value. My question is if I need to use a string as the key type, how can I overload the < and operators for string type keys only?? In template specialization we have to specialize the whole class with the type we need as I understand it. Is there any way I can do this in a better way?? What if I add a separate Key class and use it as the template type for Key? Thank You!!

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• Android: How to set the contents of a Edit text from a Button click?

  - by primal

  Hi, I am a rookie to android. I am thinking of implementing a simple calculator in android to get a hold of the basics in android. I want to display a keypad with numbers and mathematical operations and when the user presses the keys the corresponding number is displayed in edit text. I tried using gettext() and updating the contents of edit text but it shows just the contents of pressed button. Also how do I read the contents of button so as to do mathematical operations in code? Any help would be much appreciated. regards, Primal

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• Dynamic binding in C++

  - by chmike

  I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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• Where to place the login/authentication related actions in MVC

  - by rogeriopvl

  I've searched around and found that when implementing an authentication module in MVC architecture some people opt to place the login related actions in the User controller while others place it in a controller dedicated to authentication only. In pseudo-java-like code: class UserController extends Controller { public login() { //... } } Accessed with http://mydomain.com/user/login. vs. class AuthController extends Controller { public login() { //... } } Accessed with http://mydomain.com/auth/login. I would like to know which approach is better, and why. That is, if there's really any difference at all. Thanks in advance.

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• Manage dirty rect efficiently

  - by Tianzhou Chen

  Hi all, I am implementing a view system and I want to keep track of all the dirty rects. It seems my dirty rect management is a bottleneck for the whole system. On one hand, invalidating the bounding box of the dirty region seems to be an easy approach. But in the situation like this: Say I have a client area of 100x100; I have a dirty rect with (0, 0, 1, 1) and another dirty rect with (99, 99, 1, 1). Invalidating the bounding box which turns out to be 100x100 is not efficient at all. So I want to ask if someone can give any hint or give me a link of the related literatures. Thanks in advance!

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• What is the difference between IEditableObject and IRevertibleChangeTracking?

  - by open-collar

  What is the difference between IEditableObject and IRevertibleChangeTracking (both from the System.ComponentModel namespace)? It looks as if the first supports explicit transaction whilst the second is more implicit - but the net result is the same. How should I go about implementing this in code? At the moment I do nothing in BeginEdit and call RejectChanges and AcceptChanges in EndEdit and CancelEdit respectively. My problem is that this will also accept the changes made prior to the BeginEdit. Is that really what MS wanted or am I trying to implement two mutually exclusive interfaces?

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• How to convince a colleague that code duplication is bad?

  - by vitaut

  A colleague of mine was implementing a new feature in a project we work on together and he did it by taking a file containing the implementation of a similar feature from the same project, creating a copy of it renaming all the global declarations and slightly modifying the implementation. So we ended up with two large files that are almost identical apart from renaming. I tried to explain that it makes our project more difficult to maintain but he doesn't want to change anything saying that it is easier for him to program in such way and that there is no reason to fix the code if it "ain't broke". How can I convince him that such code duplication is a bad thing? It is related to this questions, but I am more interested in the answers targeted to a technical person (another programmer), for example a reference to an authoritative source like a book would be great. I have already tried simple arguments and haven't succeeded.

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• Pass a class as a parameter?

  - by JuBu1324

  I have been lead to believe that it is possible to pass a class as a method parameter, but I'm having trouble implementing the concept. Right now I have something like: - (id)navControllerFromView:(Class *)viewControllerClass title:(NSString *)title imageName:(NSString *)imageName { viewControllerClass *viewController = [[viewControllerClass alloc] init]; UINavigationController *thisNavController = [[UINavigationController alloc] initWithRootViewController: viewController]; thisNavController.tabBarItem = [[UITabBarItem alloc] initWithTitle: title image: [UIImage imageNamed: imageName] tag: 3]; return thisNavController; } and I call it like this: rootNavController = [ self navControllerFromView:RootViewController title:@"Contact" imageName:@"my_info.png" ]; What's wrong with this picture?

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