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• PubSubHubBub Hubs

  - by PartlyCloudy

  Hi, I'm currently building a live web application based upon the PubSubHubBub protocol. However, I encountered several issues. First, I'm in search of a hub application that I can run on my server. There are several applications, but most of them are not mature yet, or they don't support the 0.3 spec. The official google hub runs on the Google App Engine and can even be executed locally. Unfortunately, "Tasks will not run automatically. Push the 'Run' button to execute each task." This behaviour is useful for debugging and understanding the workflow, but in some live tests, it would be nice not to invoke all tasks manually. Is there a way to tweak the local app engine due automatically run tasks? Next, I have a question concerning the spec itself. The Google reference implementation provides the initial publish method bound to the outpoint uri + /publish. But this is not reflected in the specs. So are there any mature hubs that can be run locally for debugging? Or are there ways to configure the offical google app engine hub to run locally and to execute tasks directly? Thanks in advance

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• Perceptron Classification and Model Training

  - by jake pinedo

  I'm having an issue with understanding how the Perceptron algorithm works and implementing it. cLabel = 0 #class label: corresponds directly with featureVectors and tweets for m in range(miters): for point in featureVectors: margin = answers[cLabel] * self.dot_product(point, w) if margin <= 0: modifier = float(lrate) * float(answers[cLabel]) modifiedPoint = point for x in modifiedPoint: if x != 0: x *= modifier newWeight = [modifiedPoint[i] + w[i] for i in range(len(w))] w = newWeight self._learnedWeight = w This is what I've implemented so far, where I have a list of class labels in answers and a learning rate (lrate) and a list of feature vectors. I run it for the numbers of iterations in miter and then get the final weight at the end. However, I'm not sure what to do with this weight. I've trained the perceptron and now I have to classify a set of tweets, but I don't know how to do that. EDIT: Specifically, what I do in my classify method is I go through and create a feature vector for the data I'm given, which isn't a problem at all, and then I take the self._learnedWeight that I get from the earlier training code and compute the dot-product of the vector and the weight. My weight and feature vectors include a bias in the 0th term of the list so I'm including that. I then check to see if the dotproduct is less than or equal to 0: if so, then I classify it as -1. Otherwise, it's 1. However, this doesn't seem to be working correctly.

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• Entity Framework 4 / POCO - Where to start?

  - by Basiclife

  Hi, I've been programming for a while and have used LINQ-To-SQL and LINQ-To-Entities before (although when using entities it has been on a Entity/Table 1-1 relationship - ie not much different than L2SQL) I've been doing a lot of reading about Inversion of Control, Unit of Work, POCO and repository patterns and would like to use this methodology in my new applications. Where I'm struggling is finding a clear, concise beginners guide for EF4 which doesn't assume knowledge of EF1. The specific questions I need answered are: Code first / model first? Pros/cons in regards to EF4 (ie what happens if I do code first, change the code at a later date and need to regenerate my DB model - Does the data get preserved and transformed or dropped?) Assuming I'm going code-first (I'd like to see how EF4 converts that to a DB schema) how do I actually get started? Quite often I've seen articles with entity diagrams stating "So this is my entity model, now I'm going to ..." - Unfortunately, I'm unclear if they're created the model in the designer, saved it to generate code then stopped any further auto-code generation -or- They've coded (POCO)? classes and the somehow imported them into the deisgner view? I suppose what I really need is an understanding of where the "magic" comes from and how to add it myself if I'm not just generating an EF model directly from a DB. I'm aware the question is a little vague but I don't know what I don't know - So any input / correction / clarification appreciated. Needless to say, I don't expect anyone to sit here and teach me EF - I'd just like some good tutorials/forums/blogs/etc. for complete entity newbies Many thanks in advance

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• EAGLContext, EAGLSharegroups, RenderBuffers, FrameBuffers, oh my!

  - by quixoto

  Hi all, I'm trying to wrap my head around the OpenGL object model on iPhone OS. I'm currently rendering into a few different UIViews (build on CAEAGLayers) on the screen. I currently have each of these as using separate EAGLContext, each of which has a color renderbuffer and a framebuffer. I'm rendering similar things in them, and I'd like to share textures between these instances to save memory overhead. My current understanding is that I could use the same setup (some number of contexts, each with a FBO/RBO) but if I spawn the later ones using the EAGLShareGroup of the first one, then I can simply use the texture names (GLuints) from the first one in the later ones. Is this accurate? If this is the case, I guess the followup question is: what's the benefit to having it be a "sharegroup"? Could I just reuse the same context, and attach multiple FBOs/RBOs to that context? I think I'm struggling with the abstraction layer of a sharegroup, which seems to share "objects" (textures and other named things) but not "state" (matrices, enabled/disabled states) which are owned by the context. What's the best way to think of this? Thanks for any enlightenment!

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• Handling XMLHttpRequest to call external application

  - by Ian

  I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls. The situation: The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status. The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database. In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem. What I think I want: Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available). C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding. How do I do this? Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents? Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces? Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch? Thanks for any help! I am really having trouble learning about the server side of these technologies.

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• passive view and display logic

  - by genesys

  Hi! In MVC and MVP and similar patterns there's often the approach of the "passive view" which is as stupid as possible. This should facilitate unit testing and create a clearer separation of view and model. I know that those patterns come in very different flavours and especially the understanding of MVP seems to differ from article to article. Therefore my question is not "how do i implement this pattern correctly". I want to improve view and model separation and go for better testability of the application. Therefore i'd like to go for a passive view. But my question is, where would you put logic that is clearly only view related? like a textviewer should scroll the text when the scrollbar is moved. would you put the logic for this into the Presenter? Let's say the textviewer has some extended functionality. like setting markings on textpassages. The logic for this makes clearly sense to be put into the Presenter. However, if it is mixed with all the 'direct' logic of the view (like scrolling the text) the Presenter could become very big, which is also not really a nice design. So my question is where to put display related logic of a passive view and what functionallity to mix in the Presenter. Thanks!

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• forks in C - exercise

  - by Zka

  I try to repeat and learn more advanced uses and options when cutting trees with forks in the jungle of C. But foolishly I find an example which should be very easy as I have worked with forks before and even written some code, but i can't understand it fully. Here comes : main() { if (fork() == 0) { if (fork() == 0) { printf("3"); } else if ((wait(NULL)) > 0) { printf("2"); } } else { if (fork() == 0) { printf("1"); exit(0); } if (fork() == 0) { printf("4"); } } printf("0"); return 0; } Possible solutions are : 3201040 3104200 1040302 4321000 4030201 1403020 where 2, 5 and 6 are correct answers. First of all, shouldn't there be four zeroes in the output? Second... How does one come to the solution at all? Been doing this on paper for almost an hour and I'm not even close to understanding why the given solution are more correct than the false ones (except for nr3 as it can't end with 2 since a 0 must follow). Anyone with his forks in check who can offer some good explanation?

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• getchar does not stop when using scanf

  - by Oz123

  I am have a difficulty understanding getchar(). In the following program getchar works as expected: #include <stdio.h> int main() { printf("Type Enter to continue..."); getchar(); return 0; } However, in the following program, getchar does not create a delay and the program ends: #include <stdio.h> int main() { char command[100]; scanf("%s", command ); printf("Type Enter to continue..."); getchar(); return 0; } I have the following weired workaround, which works, but I understand why: #include <stdio.h> int main() { char command[100]; int i; scanf("%s", command ); printf("Type Enter to continue..."); while ( getchar() != '\n') { i=0; } getchar(); return 0; } So my questions are: 1. What is scanf doing? Why does scanf do this ? 2. Why is my work around working? 3. What is a good way to emulate the following Python code: raw_input("Type Enter to continue")

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• Key strokes in wpf window hosted in MFC ActiveX running in Internet Explorer

  - by user310046

  We have an MFC ActiveX control created in Visual Studio 2008 with CLR support which creates a WPF grid and shows a WPF window within that grid. This ActiveX is hosted within Internet Explorer and it shows up and works nicely except that the tab key, backspace, function keys etc. does not work since they are handeled by IE instead of the WPF window. Regular characters works nicely. This is a known feature and previously when we used to have MFC based dialogs within this ActiveX we used this: http://support.microsoft.com/kb/187988. By just using this code directly the AfxGetApp()->PreTranslateMessage((LPMSG)lParam) statement will return FALSE, so I'm not able to get the key stroke to be handled by the WPF window. I beleive I need to ask the WPF application this instead of the CWinApp, but I'm not sure how and if this can be done. Does anyone have enough understanding of what's going on here to get this to work? Using XBAP instead of ActiveX is not an option as this is run in an intranet application which needs more access than the sandbox can give us. I hope this is enough information. With best regards Svein Dybvik

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• Linear feedback shift register?

  - by Mattia Gobbi

  Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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• Grails UrlMappings with .html

  - by Glennn

  I'm developing a Grails web application (mainly as a learning exercise). I have previously written some standard Grails apps, but in this case I wanted to try creating a controller that would intercept all requests (including static html) of the form: <a href="/testApp/testJsp.jsp">test 1</a> <a href="/testApp/testGsp.gsp">test 2</a> <a href="/testApp/testHtm.htm">test 3</a> <a href="/testApp/testHtml.html">test 4</a> The intent is to do some simple business logic (auditing) each time a user clicks a link. I know I could do this using a Filter (or a range of other methods), however I thought this should work too and wanted to do this using a Grails framework. I set up the Grail UrlMappings.groovy file to map all URLs of that form (/$myPathParam?) to a single controller: class UrlMappings { static mappings = { "/$controller/$action?/$id?"{ constraints { } } "/$path?" (controller: 'auditRecord', action: 'showPage') "500"(view:'/error') } } In that controller (in the appropriate "showPage" action) I've been printing out the path information, for example: def showPage = { println "params.path = " + params.path ... render(view: resultingView) } The results of the println in the showPage action for each of my four links are testJsp.jsp testGsp.gsp testHtm.htm testHtml Why is the last one "testHtml", not "testHtml.html"? In a previous (Stack Overflow query) Olexandr encountered this issue and was advised to simply concatenate the value of request.format - which, indeed, does return "html". However request.format also returns "html" for all four links. I'm interested in gaining an understanding of what Grails is doing and why. Is there some way to configure Grails so the params.path variable in the controller shows "testHtml.html" rather than stripping off the "html" extension? It doesn't seem to remove the extension for any other file type (including .htm). Is there a good reason it's doing this? I know that it is a bit unusual to use a controller for static html, but still would like to understand what's going on.

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• Loading UITableView form UIView

  - by Amarpreet

  Hi Guys, I am working on navigation based application in which i can navigate to many views starting from default UITableView which is starting view in application template. I have added another UIView and added tableView control on that UIView. I am calling that view form one of the many views on a button click. Its showing the view but not populating the data in the table. And I also want to handle the event when user taps on the cell of the table of that view. Below is the Code I am using on button click: if(self.lstView == nil) { ListViewController *viewController = [[ListViewController alloc] initWithNibName:@"ListViewController" bundle:nil]; self.lstView = viewController; [viewController release]; } [self.navigationController pushViewController:lstView animated:YES]; self.lstView.title = @"Select";//@"System"; [self.lstView.tblList.dataSource fillList]; Below is the fillList function code: -(NSArray *)fillList { NSArray *tempArray = [[[NSArray alloc] initWithObjects:@"Item 1" , @"Item 2" , nil]autorelease]; return tempArray; } I am pretty new in Iphone programming and don't have much understanding. Helping with detailed description and code will be highly appreciated. Thanks.

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• rpy2: Converting a data.frame to a numpy array

  - by Mike Dewar

  I have a data.frame in R. It contains a lot of data : gene expression levels from many (125) arrays. I'd like the data in Python, due mostly to my incompetence in R and the fact that this was supposed to be a 30 minute job. I would like the following code to work. To understand this code, know that the variable path contains the full path to my data set which, when loaded, gives me a variable called immgen. Know that immgen is an object (a Bioconductor ExpressionSet object) and that exprs(immgen) returns a data frame with 125 columns (experiments) and tens of thousands of rows (named genes). robjects.r("load('%s')"%path) # loads immgen e = robjects.r['data.frame']("exprs(immgen)") expression_data = np.array(e) This code runs, but expression_data is simply array([[1]]). I'm pretty sure that e doesn't represent the data frame generated by exprs() due to things like: In [40]: e._get_ncol() Out[40]: 1 In [41]: e._get_nrow() Out[41]: 1 But then again who knows? Even if e did represent my data.frame, that it doesn't convert straight to an array would be fair enough - a data frame has more in it than an array (rownames and colnames) and so maybe life shouldn't be this easy. However I still can't work out how to perform the conversion. The documentation is a bit too terse for me, though my limited understanding of the headings in the docs implies that this should be possible. Anyone any thoughts?

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• How can I fix this clang warning: "Object with +0 retain counts returned to caller where +1 (owning)

  - by mipadi

  I have a piece of Objective-C code that looks like the following: - (NSString *)copyData:(NSData *)data { NSString *path = [[[self outputDirectory] stringByAppendingPathComponent:@"archive"] stringByAppendingPathExtension:@"zip"]; NSLog(@"Copying data to %@", path); [data writeToFile:path atomically:NO]; return path; } The code is called from an initializer that looks like this: - (id)initWithData:(NSData *)data { if ((self = [super init]) != nil) { NSString *path = [self copyData:data]; // Line 41 (referenced in warning, shown below) return [self initWithContentsOfFile:path]; } return self; } When running the clang static analyzer, I get the following warnings for the path variable: Potential leak of an object allocated on line 41 and stored into 'path' Object with +0 retain counts returned to caller where +1 (owning) retain count is expected I'm confused. My understanding is that stringByAppendingPathComponent should not return an autoreleased string, so it should have a net retain count of 0. (Obviously I don't want to retain it.) I've tried altering copyData: to return the following, but it didn't get rid of the warning: return [[path retain] autorelease]; So what's the deal with this warning?

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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• Serial.begin(speed, config) not compiling for Leonardo Board

  - by forgemo

  I would like to configure my serial communication to have no parity, 1 start- and 2 stop-bits. The documentation for Serial.begin(speed, config) states: (...) An optional second argument configures the data, parity, and stop bits. The default is 8 data bits, no parity, one stop bit. The documentation also lists the possible configuration-values. According to my (limited) understanding, I need SERIAL_7N2 or SERIAL_8N2 to meet my requirements. (I'm not sure how the data-bits relate to the the 1-start-bit that I need.) However, I can't even compile because I have no idea how to supply that config value to the begin method. (I don't have much Arduino/C++ experience) I've tried in my code the following two variants: Serial.begin(9600, SERIAL_8N2); Serial.begin(9600, "SERIAL_8N2"); Am I missing something? Additional Information: Serial.begin(speed, config) has been introduced with the latest Arduino 1.0.2 IDE version. The code defining/implementing the begin methods can be found here. HardwareSerial.h HardwareSerial.cpp Edit: According to the replies from PeterJ and borges, the following variant is correct. Serial.begin(9600, SERIAL_8N2); However, it's still not working. I found that the compile error doesn't occur if I change the configured board from my Arduino Leonardo to Arduino uno. Therefore, it could be a bug occurring only with a subset of boards ... or maybe it's not supported?!

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• In C#, are event handler arguments covariant?

  - by Roger Lipscombe

  Maybe covariant's not the word, but if I have a class that raises an event, with (e.g.) FrobbingEventArgs, am I allowed to handle it with a method that takes EventArgs? Here's some code: class Program { static void Main(string[] args) { Frobber frobber = new Frobber(); frobber.Frobbing += FrobberOnFrobbing; frobber.Frob(); } private static void FrobberOnFrobbing(object sender, EventArgs e) { // Do something interesting. Note that the parameter is 'EventArgs'. } } internal class Frobber { public event EventHandler<FrobbingEventArgs> Frobbing; public event EventHandler<FrobbedEventArgs> Frobbed; public void Frob() { OnFrobbing(); // Frob. OnFrobbed(); } private void OnFrobbing() { var handler = Frobbing; if (handler != null) handler(this, new FrobbingEventArgs()); } private void OnFrobbed() { var handler = Frobbed; if (handler != null) handler(this, new FrobbedEventArgs()); } } internal class FrobbedEventArgs : EventArgs { } internal class FrobbingEventArgs : EventArgs { } The reason I ask is that ReSharper seems to have a problem with (what looks like) the equivalent in XAML, and I'm wondering if it's a bug in ReSharper, or a mistake in my understanding of C#.

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• Hazelcast Distributed Executor Service KeyOwner

  - by János Veres

  I have problem understanding the concept of Hazelcast Distributed Execution. It is said to be able to perform the execution on the owner instance of a specific key. From Documentation: <T> Future<T> submitToKeyOwner(Callable<T> task, Object key) Submits task to owner of the specified key and returns a Future representing that task. Parameters: task - task key - key Returns: a Future representing pending completion of the task I believe that I'm not alone to have a cluster built with multiple maps which might actually use the same key for different purposes, holding different objects (e.g. something along the following setup): IMap<String, ObjectTypeA> firstMap = HazelcastInstance.getMap("firstMap"); IMap<String, ObjectTypeA_AppendixClass> secondMap = HazelcastInstance.getMap("secondMap"); To me it seems quite confusing what documentation says about the owner of a key. My real frustration is that I don't know WHICH - in which map - key does it refer to? The documentation also gives a "demo" of this approach: import com.hazelcast.core.Member; import com.hazelcast.core.Hazelcast; import com.hazelcast.core.IExecutorService; import java.util.concurrent.Callable; import java.util.concurrent.Future; import java.util.Set; import com.hazelcast.config.Config; public void echoOnTheMemberOwningTheKey(String input, Object key) throws Exception { Callable<String> task = new Echo(input); HazelcastInstance hz = Hazelcast.newHazelcastInstance(); IExecutorService executorService = hz.getExecutorService("default"); Future<String> future = executorService.submitToKeyOwner(task, key); String echoResult = future.get(); } Here's a link to the documentation site: Hazelcast MultiHTML Documentation 3.0 - Distributed Execution Did any of you guys figure out in the past what key does it want?

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• Do the new NoPIA and Type Equivalence features in C#/.NET 4.0 mean Microsoft.mshtml.dll is no longer

  - by jpierson

  I'm maintaining a WPF based application which contains a WinForms based WebBrowser control that based on the IE web browser control. When we deploy, we have had to also supply Microsoft.mshtml.dll and do some custom configuration stuff for our ClickOnce publishing process as well in order to get things to work. I'm curious that with the new NoPIA and Type Equivalence features and dynamic type capabilities in C# 4.0 can we expect that if we upgrade that we can remove the dependencies on the Microsoft.mshtml.dll assembly? If so this will not only reduce the size of our deployment quite a bit but will also simplify our publishing process as well. It is my understanding that we should be able embed the types that normally get automatically generated into extra assemblies for COM types such as the MapPoint Control by Visual Studio. I don't know if this also applies to the Microsoft.mshtml.dll or even how it is done even in the most simple of cases. If somebody could provide an explanation about what the practical impact of these new features are on a project that relies on COM interop and especially the Microsoft.mshtml.dll assembly it would be of great help to me.

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• Getting a variable into another class through properties or button tags with Iphone SDK?

  - by MarcZero

  Hello. I have been pounding my head against a wall trying to figure out what I think is a simple thing to do, but I have, so far, been unable to figure it out with the iPhone SDK. I have a view with 4 buttons. When I push the buttons, I have another view called and come up to take over the screen. I want to have a simple variable passed from the old view to the new view. The purpose of this is to know what button was pressed out of the four identical ones. (trying to get an int value of 1 through 4) Here is what I have tried so far: I initially tried to call the variable from the class itself. My understanding was that my new view was only sitting on top of the old view, so it should not have been released. I could not get access to the variable as the variable was said to not be declared. I then tried to create a method that would return the int value. Again, the view class was not seen and was being declared as a "first use" of it. I then attempted to follow another similar post on here that suggested to try and send the button tag number to some part of the new view. I attempted to do this by setting the new views button title but I still cannot figure out a way to code it without coming up with errors. I am just looking for what method would be the best for me to pursue. I have no problem going back and reading the books on Objective-C, but I'm just trying to figure out which way I should concentrate on. Thank you for any insight.

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• How to access a superclass's class attributes in Python?

  - by Brecht Machiels

  Have a look at the following code: class A(object): defaults = {'a': 1} def __getattr__(self, name): print('A.__getattr__') return self.get_default(name) @classmethod def get_default(cls, name): # some debug output print('A.get_default({}) - {}'.format(name, cls)) try: print(super(cls, cls).defaults) # as expected except AttributeError: #except for the base object class, of course pass # the actual function body try: return cls.defaults[name] except KeyError: return super(cls, cls).get_default(name) # infinite recursion #return cls.__mro__[1].get_default(name) # this works, though class B(A): defaults = {'b': 2} class C(B): defaults = {'c': 3} c = C() print('c.a =', c.a) I have a hierarchy of classes each with its own dictionary containing some default values. If an instance of a class doesn't have a particular attribute, a default value for it should be returned instead. If no default value for the attribute is contained in the current class's defaults dictionary, the superclass's defaults dictionary should be searched. I'm trying to implement this using the recursive class method get_default. The program gets stuck in an infinite recursion, unfortunately. My understanding of super() is obviously lacking. By accessing __mro__, I can get it to work properly though, but I'm not sure this is a proper solution. I have the feeling the answer is somewhere in this article, but I haven't been able to find it yet. Perhaps I need to resort to using a metaclass?

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• MySQL GIS and Spatial Extensions - how to map regions and query against them

  - by chibineku

  I am trying to make a smartphone app which will return a list of users within a certain proximity, say 100m. It's easy to get the coordinates of my BlackBerry and write them to a database, but in order to return a list of other users within 100m, I need to pull every other record from the database and compare the distance between the two points, checking to see if it's within range, before outputting that user's information. This is going to be time consuming if there are many users involved. So I would like to map areas (countries, cities, I'm not yet sure of the resolution I'll need) so that I can first target a smaller subset of all users. This will save on processing time. I have read the basics of GIS and spatial querying on the mysql website but to be honest the query is over my head and I hate copying and pasting code without understanding it. Plus it only checks for proximity - I want to first check if a coordinate falls within a certain area. Does anyone have any experience of such matters and feel like giving me some pointers? Resources such as any preexisting databases of points describing countries as polygons would be really helpful too. Many thanks to anyone who takes the time :)

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• Final classes in Python 3.x- something Guido isn't telling me?

  - by GlenCrawford

  This question is built on top of many assumptions. If one assumption is wrong, then the whole thing falls over. I'm still relatively new to Python and have just entered the curious/exploratory phase. It is my understanding that Python does not support the creating of classes that cannot be subclassed (final classes). However, it seems to me that the bool class in Python cannot be subclassed. This makes sense when the intent of the bool class is considered (because bool is only supposed to have two values: true and false), and I'm happy with that. What I want to know is how this class was marked as final. So my question is: how exactly did Guido manage to prevent subclassing of bool? >>> class TestClass(bool): pass Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> class TestClass(bool): TypeError: type 'bool' is not an acceptable base type Related question: http://stackoverflow.com/questions/2172189/why-i-cant-extend-bool-in-python

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• How to handle Lightbox with Capybara , Selenium and Cucumber framework?

  - by Sushil

  Im trying to run test suite that will handle the jquery light-box. Light box contains a text-area and a submit button. Before Light box appears both of these fields are hidden. But selenium framework not understanding the visibility of these element in Light box. It just shows following error. And I fill comment box with "Text !!" # features/step_definitions/web_steps.rb:333 Element is not currently visible and so may not be interacted with (Selenium::WebDriver::Error::ElementNotVisibleError) [remote server] file:///tmp/webdriver-profile20120403-6182-1rd9z23/extensions/[email protected]/components/command_processor.js:9509:in `unknown' [remote server] file:///tmp/webdriver-profile20120403-6182-1rd9z23/extensions/[email protected]/components/command_processor.js:10510:in `unknown' [remote server] file:///tmp/webdriver-profile20120403-6182-1rd9z23/extensions/[email protected]/components/command_processor.js:10529:in `unknown' [remote server] file:///tmp/webdriver-profile20120403-6182-1rd9z23/extensions/[email protected]/components/command_processor.js:10534:in `unknown' [remote server] file:///tmp/webdriver-profile20120403-6182-1rd9z23/extensions/[email protected]/components/command_processor.js:10482:in `unknown' (eval):2:in `send' (eval):2:in `fill_in' ./features/step_definitions/web_steps.rb:335:in `/^I fill comment box with "([^"]*)"$/' features/courses_flow.feature:21:in `And I fill comment box with "Text !!"'

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• Accessing previous activity instances in a sequence activity

  - by Dan Revell

  This has a rather SharePoint spin to it but the problem is straight workflow. I've got a parallel replication activity which contains a sequence activity. The sequence activity contains a CreateTask activity, a CodeActivity, a OnTaskChanged activity and finally a CompleteTask activity. The idea is to create a task for each username passed into the ReplicatorActivity.InitialChildData property. Typically in workflow I bind a field to the CreateTask.TaskId and CreateTask.TaskProperties and inside the CreateTask.MethodInvoking I set these through the local bound fields. This works and my tasks all get created properly. However in the CodeActivity that follows, I want to then access the TaskProperties. The problem I am encountering is that this field holds the values of the final task to be created as the CreateTask runs for all the replications before the CodeActivity gets to runs. From the CodeActivity, here are two ways I've tried to access the CreateTask activity instance from the same context or instance or whatever the terminology is for the replicated sequence. CreateTask task = ((CreateTask)sender.Parent.GetActivityByName("createSoftwareRequestTask", true)); CreateTask createTask = (CreateTask)sender.Parent.Activities[0]; Unfortunately the CreateTask activities both refer back to the last task to be created and not the task from the context that the CodeActivity is executing within. Two reasons why this might be that I can think of. I'm not accessing the correct instance with my code. I am accessing the correct instance, but as the properties I require were bound to and set through local fields then their previous data was overwritten. I'm hitting a brick wall with my understanding of workflow with this and would very much appreciate some assistance here.

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