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  • Having trouble understanding some code (Ruby on Rails)

    - by user284194
    I posted a question awhile ago asking how I could limit the rate at which a form could be submitted from a rails application. I was helped by a very patient user and their solution works great. The code was for my comments controller, and now I find myself wanting to add this functionality to another controller, my Messages controller. I immediately tried reusing the working code from the comments controller but I couldn't get it to work. Instead of asking for the working code, could someone please help me understand my working comment controller code? class CommentsController < ApplicationController #... before_filter :post_check def record_post_time cookies[:last_post_at] = Time.now.to_i end def last_post_time Time.at((cookies[:last_post_at].to_i rescue 0)) end MIN_POST_TIME = 2.minutes def post_check return true if (Time.now - last_post_time) > MIN_POST_TIME flash[:warning] = "You are trying to reply too fast." @message = Message.find(params[:message_id]) redirect_to(@message) return false end #... def create @message = Message.find(params[:message_id]) @comment = @message.comments.build(params[:comment]) if @comment.save record_post_time flash[:notice] = "Replied to \"#{@message.title}\"" redirect_to(@message) else render :action => "new" end end def update @message = Message.find(params[:message_id]) @comment = Comment.find(params[:id]) if @comment.update_attributes(params[:comment]) record_post_time redirect_to post_comment_url(@message, @comment) else render :action => "edit" end end #... end My Messages controller is pretty much a standard rails generated controller with a few before filters and associated private methods for DRYing up the code and a redirect for non existent pages. I'll explain how much of the code I understand. When a comment is created, a cookie is created with a last_post_time value. If they try to post another comment, the cookie is checked if the last one was made in the last two minutes. If it was a flash warning is displayed and no comment is recorded. What I don't really understand is how the post_check method works and how I can adapt it for my simpler posts controller. I thought I could reuse all the code in the message controller with the exception of the line: @message = Message.find(params[:message_id]) # (don't need the redirect code) in the post_check method. But it trips up on the "record_post_time" in the create action/method. I really want to understand this. Can someone explain why this doesn't work? I greatly appreciate you reading my lengthy question.

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  • Getting up to speed on modern architecture

    - by Matt Thrower
    Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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  • C++ Exam Question

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • php regex guitar tab (tabs or tablature, a type of music notation)

    - by John
    I am in the process of creating a guitar tab to rtttl (Ring Tone Text Transfer Language) converter in PHP. In order to prepare a guitar tab for rtttl conversion I first strip out all comments (comments noted by #- and ended with -#), I then have a few lines that set tempo, note the tunning and define multiple instruments (Tempo 120\nDefine Guitar 1\nDefine Bass 1, etc etc) which are stripped out of the tab and set aside for later use. Now I essentially have nothing left except the guitar tabs. Each tab is prefixed with it's instrument name in conjunction with the instrument name noted prior. Some times we have tabs for 2 separate instruments that are linked because they are to be played together, ie a Guitar and a Bass Guitar playing together. Example 1, Standard Guitar Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| Example 2, Conjunction Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| I have considered other methods of identifying the tabs with no solid results. I am hoping that someone who does regular expressions could help me find a way to identify a single guitar tab and if possible also be able to match a tab with multiple instruments linked together. Once the tabs are in an array I will go through them one line at a time and convert them into rtttl lines (exploded at each new line "\n"). I do not want to separate the guitar tabs in the document via explode "\n\n" or something similar because it does not identify the guitar tab, rather, it is identifying the space between the tabs - not on the tabs themselves. I have been messing with this for about a week now and this is the only major hold up I have. Everything else is fairly simple. As of current, I have tried many variations of the regex pattern. Here is one of the most recent test samples: <?php $t = " |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| "; preg_match_all("/^.*?(\\|).*?(\\|)/is",$t,$p); print_r($p); ?> It is also worth noting that inside the tabs, where the dashes and #'s are, you may also have any variation of letters, numbers and punctuation. The beginning of each line marks the tuning of each string with one of the following case insensitive: a,a#,b,c,c#,d,d#,e,f,f#,g or g. Thanks in advance for help with this most difficult problem.

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  • NVIDIA graphics driver in Ubuntu 12.04

    - by user924501
    So my overall goal is that I want to be able to code with CUDA enabled applications. However, upon many days of searching, using installation walkthroughs, and reinstalling countless times after driver failure... I'm now here as a last resort. I cannot get Ubuntu 12.04 LTS to install the NVIDIA 295.59 driver for my GeForce GT 540M NVIDIA graphics card. My main system specs is as follows... (I believe having the Intel processor may be the problem) DELL Laptop XPS L502X Intel® Core™ i7-2620M CPU @ 2.70GHz × 4 Intel Integrated Graphics 64 bit NVIDIA GeForce GT 540M Ubuntu 12.04 LTS All other specs are irrelevant unless I forgot something? Methods Tried: aptitude install nvidia-current (all packages) Results: Nothing really happened. Nothing in the additional drivers menu appeared, nor was the NVIDIA X Server settings application allowing access because it thought there was no NVIDIA X Server installed. Downloaded driver from nvidia.com. Set nomodeset in the grub boot menu through /boot/grub/grub.cfg Went to console and turned off lightdm. Installed the driver, but it said the pre-install failed? (mean anything?) Started up lightdm again. Results: NVIDIA X Server settings still didn't notice it. Even tried to do nvidia-xconfig multiple times. I also went into the config file to make sure the driver setting said "nvidia". aptitude install nvidia-173 (all packages) Results: Couldn't find the xorg-video-abi-10 virtual package. It was nowhere to be found and the ubuntu forums everywhere had no answers. Lots of people were having this problem. This is easily done in windows, simply download the driver and debug in visual studio with no problems at all. I'd like clear step-by-step instructions on how I should go about this. I'm relatively new to linux but I can find my way around pretty well so you aren't talking to a straight-up beginner. Also, if you think another thread may have the answer please post because I was having a hard time looking for my specific type of problem. TL;DR I want to have access to my GPU so I can code with CUDA while in Ubuntu 12.04 on my 64 bit laptop that also has Intel integrated graphics on the processor. Solution: sudo apt-add-repository ppa:ubuntu-x-swat/x-updates && sudo apt-get update && sudo apt-get upgrade && sudo apt-get install nvidia-current

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  • TestNG - Factories and Dataproviders

    - by Tim K
    Background Story I'm working at a software firm developing a test automation framework to replace our old spaghetti tangled system. Since our system requires a login for almost everything we do, I decided it would be best to use @BeforeMethod, @DataProvider, and @Factory to setup my tests. However, I've run into some issues. Sample Test Case Lets say the software system is a baseball team roster. We want to test to make sure a user can search for a team member by name. (Note: I'm aware that BeforeMethods don't run in any given order -- assume that's been taken care of for now.) @BeforeMethod public void setupSelenium() { // login with username & password // acknowledge announcements // navigate to search page } @Test(dataProvider="players") public void testSearch(String playerName, String searchTerm) { // search for "searchTerm" // browse through results // pass if we find playerName // fail (Didn't find the player) } This test case assumes the following: The user has already logged on (in a BeforeMethod, most likely) The user has already navigated to the search page (trivial, before method) The parameters to the test are associated with the aforementioned login The Problems So lets try and figure out how to handle the parameters for the test case. Idea #1 This method allows us to associate dataproviders with usernames, and lets us use multiple users for any specific test case! @Test(dataProvider="players") public void testSearch(String user, String pass, String name, String search) { // login with user/pass // acknowledge announcements // navigate to search page // ... } ...but there's lots of repetition, as we have to make EVERY function accept two extra parameters. Not to mention, we're also testing the acknowledge announcements feature, which we don't actually want to test. Idea #2 So lets use the factory to initialize things properly! class BaseTestCase { public BaseTestCase(String user, String password, Object[][] data); } class SomeTest { @Factory public void ... } With this, we end up having to write one factory per test case... Although, it does let us have multiple users per test-case. Conclusion I'm about fresh out of ideas. There was another idea I had where I was loading data from an XML file, and then calling the methods from a program... but its getting silly. Any ideas?

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  • Architectural Design for a Data-Driven Silverlight WP7 app

    - by Rosarch
    I have a Silverlight Windows Phone 7 app that pulls data from a public API. I find myself doing much of the same thing over and over again: In the UI, set a loading message or loading progress bar in place of where the content is Get the content, which may be already in memory, cached in isolated file storage, or require an HTTP request If the content can not be acquired (no network connection, etc), display an error message If the content is acquired, display it in the UI Keep the content in main memory for subsequent queries The content that is displayed to the user can be taken directly from a data source, such as an ObservableCollection, or it may be a query on a data source. I would like to factor out this repetitive process into a framework where ideally only the following needs to be specified: Where to display the content in the UI The UI elements to show while loading, on failure, and on success The URI of the HTTP request How to parse the HTTP response into the data structure that will kept in memory The location of the file in isolated storage, if it exists How to parse the file contents into the data structure that will be kept in memory It may sound like a lot, but two strings, three FrameworkElements, and two methods is less than the overhead that I currently have. Also, this needs to work for however the data is maintained in memory, and needs to work for direct collections and queries on those collections. My questions are: Has something like this already been implemented? Are my thoughts about the topic above fundamentally wrong in some way? Here is a design I'm thinking of: There are two components, a View and a Model. The View is given the FrameworkElements for loading, failure, and success. It is also given a reference to the corresponding Model. The View is a UserControl that is placed somewhere in the UI. The Model a class that is given the URI for the data, a method of how to parse the data, and optionally a filename and how to parse the file. It is responsible for retrieving the data and notifying the View whenever the current status (loading/fail/success) changes. If the data downloaded from the network is different from the cache, the network data takes precedence. When the app closes or is tombstoned, the model writes the data to the cache. How does that sound?

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  • Passing variables, creating instances, self, The mechanics and usage of classes: need explenation

    - by Baf
    I've been sitting over this the whole day and Im a little tired already so please excuse me being brief. Im new to python. I just rewrrote a working program, into a bunch of functions in a class and everzthings messed up. I dont know if its me but Im very surprised i couldn t find a beginners tutorial on how to handle classes on the web so I have a few questions. First of all, in the init section of the class i have declared a bunch of variables with self.variable=something. Is it correct that i should be able to access/modify these variables in every function of the class by using self.variable in that function? In other words by declaring self.variable i have made these variables, global variables in the scope of the class right? If not how do i handle self. ? Secondly how do i correctly pass arguments to the class? some example code would be cool. thirdly how do i call a function of the class outside of the class scope? some example code would be cool. fouthly how do I create an Instance of the class INITIALCLASS in another class OTHERCLASS, passing variables from OTHERCLASS to INITIALCLASS? some example code would be cool. I Want to call a function from OTHERCLASS with arguments from INITIALCLASS. What Ive done so far is. class OTHERCLASS(): def __init__(self,variable1,variable2,variable3): self.variable1=variable1 self.variable2=variable2 self.variable3=variable3 def someotherfunction(self): something=somecode(using self.variable3) self.variable2.append(something) print self.variable2 def somemorefunctions(self): self.variable2.append(variable1) class INITIALCLASS(): def __init__(self): self.variable1=value1 self.variable2=[] self.variable3='' self.DoIt=OTHERCLASS(variable1,variable2,variable3) def somefunction(self): variable3=Somecode #tried this self.DoIt.someotherfunctions() #and this DoIt.someotherfunctions() I clearly havent understood how to pass variables to classes or how to handle self, when to use it and when not, I probably also havent understood how to properly create an isntance of a class. In general i havent udnerstood the mechanics of classes So please help me and explain it to me like i have no Idea( which i dont it seems). Or point me to a thorough video, or readable tutorial. All i find on the web is super simple examples, that didnt help me much. Or just very short definitions of classes and class methods instances etc. I can send you my original code if you guys want, but its quite long. Thanks for the Help Much appreciated!

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  • Best Practices for Working with Multiple Monitors in Visual Studio 2010

    - by Clever Human
    Now that Visual Studio 2010 has support for multiple monitors, I am curious how other people have their environments arranged. I have yet to come up with an arrangement that I am really satisfied with. The current best I have come up with for my 2 monitor system is to have all code windows detached. Then, on my primary monitor, I am able to have two code windows side by side (using the Windows 7 keyboard shortcuts WinKey+LeftArrow and WinKey+RightArrow.) On my secondary monitor I put the rest of the IDE with all of the tool windows that are normally on the bottom (errors list, find window, call stack, etc...) docked where the code windows normally go. I've also tried having all those things detached and having almost nothing in the IDE proper. The problems with this layout are: Newly opened code windows always open in the IDE, not on top of one of the detached windows. Detached code windows do not remember their exact placement from session to session (they are slightly off, having me to use the winkey + arrow key shortcut again and again for each window. There seems to be no way to have the code panes aware that they are on top of one another (IE -- multiple tabs.) The CTRL+TAB shortcut always displays on top of the IDE proper. The Code Panes are always "on top" of (children of) the IDE. So clicking on any code pane brings the IDE to the foreground, even when I care only about that code pane, and not the IDE. Other more minor issues... What would go a long way to making this better is having the code panes detach such that they are tab strips that can have other code panes docked within them. The new multi-monitor support in VS2010 is good, but it still seems really lacking. Can these issues be solved with an add-in? If so, is anyone aware of one? Is there a better way to work with the IDE on multiple monitors than what I am doing? NOTE: While this question is subjective (there is certainly no "this is the best way and that's final" answer) I'd really like to know possibly better methods of working with the IDE than what I have come up with. The intent is not to start a "mine's best" flame war.

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  • How can I link axes of imshow plots for zooming and panning?

    - by Adam Fraser
    Suppose I have a figure canvas with 3 plots... 2 are images of the same dimensions plotted with imshow, and the other is some other kind of subplot. I'd like to be able to link the x and y axes of the imshow plots so that when I zoom in one (using the zoom tool provided by the NavigationToolbar), the other zooms to the same coordinates, and when I pan in one, the other pans as well. Subplot methods such as scatter and histogram can be passed kwargs specifying an axes for sharex and sharey, but imshow has no such configuration. I started hacking my way around this by subclassing NavigationToolbar2WxAgg (shown below)... but there are several problems here. 1) This will link the axes of all plots in a canvas since all I've done is get rid of the checks for a.in_axes() 2) This worked well for panning, but zooming caused all subplots to zoom from the same global point, rather than from the same point in each of their respective axes. Can anyone suggest a workaround? Much thanks! -Adam from matplotlib.backends.backend_wxagg import NavigationToolbar2WxAgg class MyNavToolbar(NavigationToolbar2WxAgg): def __init__(self, canvas, cpfig): NavigationToolbar2WxAgg.__init__(self, canvas) # overrided # As mentioned in the code below, the only difference here from overridden # method is that this one doesn't check a.in_axes(event) when deciding which # axes to start the pan in... def press_pan(self, event): 'the press mouse button in pan/zoom mode callback' if event.button == 1: self._button_pressed=1 elif event.button == 3: self._button_pressed=3 else: self._button_pressed=None return x, y = event.x, event.y # push the current view to define home if stack is empty if self._views.empty(): self.push_current() self._xypress=[] for i, a in enumerate(self.canvas.figure.get_axes()): # only difference from overridden method is that this one doesn't # check a.in_axes(event) if x is not None and y is not None and a.get_navigate(): a.start_pan(x, y, event.button) self._xypress.append((a, i)) self.canvas.mpl_disconnect(self._idDrag) self._idDrag=self.canvas.mpl_connect('motion_notify_event', self.drag_pan) # overrided def press_zoom(self, event): 'the press mouse button in zoom to rect mode callback' if event.button == 1: self._button_pressed=1 elif event.button == 3: self._button_pressed=3 else: self._button_pressed=None return x, y = event.x, event.y # push the current view to define home if stack is empty if self._views.empty(): self.push_current() self._xypress=[] for i, a in enumerate(self.canvas.figure.get_axes()): # only difference from overridden method is that this one doesn't # check a.in_axes(event) if x is not None and y is not None and a.get_navigate() and a.can_zoom(): self._xypress.append(( x, y, a, i, a.viewLim.frozen(), a.transData.frozen())) self.press(event)

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  • Global NSMutableArray doesn't seem to be holding values

    - by diatrevolo
    I have a Cocos2D iPhone application that requires a set of CGRects overlaid on an image to detect touches within them. "Data" below is a class that holds values parsed from an XML file. "delegateEntries" is a NSMutableArray that contains several "data" objects, pulled from another NSMutableArray called "entries" that lives in the application delegate. For some strange reason, I can get at these values without problems in the init function, but further down the class in question, I try to get at these values, and the application crashes without an error message (as an example, I put in the "ccTouchBegan" method which accessess this data through the "populateFieldsForTouchedItem" method. Can anyone see why these values would not be accessible from other methods? No objects get released until dealloc. Thanks in advance! @synthesize clicked, delegate, data, image, blurImage, normalImage, arrayOfRects, delegateEntries; - (id)initWithTexture:(CCTexture2D *)aTexture { if( (self=[super initWithTexture:aTexture] )) { arrayOfRects = [[NSMutableArray alloc] init]; delegateEntries = [[NSMutableArray alloc] init]; delegate = (InteractivePIAppDelegate *)[[UIApplication sharedApplication] delegate]; delegateEntries = [delegate entries]; data = [delegateEntries objectAtIndex:0]; NSLog(@"Assigning %@", [[delegateEntries objectAtIndex:0] backgroundImage]); NSLog(@"%@ is the string", [[data sections] objectAtIndex:0]); //CGRect rect; NSLog(@"Count of array is %i", [delegateEntries count]); //collect as many items as there are XML entries for(int i=0; i<[delegateEntries count]; i++) { if([[delegateEntries objectAtIndex:i] xPos]) { NSLog(@"Found %i items", i+1); [arrayOfRects addObject:[NSValue valueWithCGRect:CGRectMake([[[delegateEntries objectAtIndex:i] xPos] floatValue], [[[delegateEntries objectAtIndex:i] yPos] floatValue], [[[delegateEntries objectAtIndex:i] xBounds] floatValue], [[[delegateEntries objectAtIndex:i] yBounds] floatValue])]]; } else { NSLog(@"Nothing"); } } //remove the following once the NSMutableArray from above works (legacy) blurImage = [[NSString alloc] initWithString:[data backgroundBlur]]; NSLog(@"5"); normalImage = [[NSString alloc] initWithString:[data backgroundImage]]; clicked = NO; } return self; } And then: - (void)populateFieldsForTouchedItem:(TouchedRect)touchInfo { Data *touchDatum = [[Data alloc] init]; touchDatum = [[self delegateEntries] objectAtIndex:touchInfo.recordNumber]; NSLog(@"Assigning %@", [[[self delegateEntries] objectAtIndex:touchInfo.recordNumber] backgroundImage]); rect = [[arrayOfRects objectAtIndex:touchInfo.recordNumber] CGRectValue]; image = [[NSString alloc] initWithString:[[touchDatum sections] objectAtIndex:0]]; [touchDatum release]; } - (BOOL)ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event { TouchedRect touchInfo = [self containsTouchLocation:touch]; NSLog(@"Information pertains to %i", touchInfo.recordNumber); if ( !touchInfo.touched && !clicked ) { //needed since the touch location changes when zoomed NSLog(@"NOPE"); return NO; } [self populateFieldsForTouchedItem:touchInfo]; NSLog(@"YEP"); return YES; }

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  • Calling a JAVA method from C++ with JNI, no parameters

    - by PRNDL Development Studios
    Please bear with me, I am an iPhone developer and this whole android this confuses me a bit. I have some c++ methods that are called from a cocos2d-x CCMenuItem. Therefore I cannot send any parameters, according to the docs. I need to open a url with the android browser which will require me to call a JAVA function to start a new intent. I understand that I need to create a VM, however the below code gives me the error: jni/../../Classes/MyClass.cpp:184: error: 'JNI_CreateJavaVM' was not declared in this scope I was looking at this thread: Calling a java method from c++ in Android But he uses parameters, and I can't do that. And I don't see where those are in his code to just make them myself. I don't know what the string should be in the 'Find Class' method. Also, I assume it is pretty terrible to create a new VM instance in every method I need to call. How would I create one as a singleton to use across the board? This is my c++ code called by my menu item: #include <jni.h> ... JavaVM *vm; // Global ... void OptionsScene::website(){ JNIEnv *env; JavaVMInitArgs vm_args; vm_args.version = JNI_VERSION_1_2; vm_args.nOptions = 0; vm_args.ignoreUnrecognized = 1; jint result = JNI_CreateJavaVM(&vm, (void **)&env, &vm_args); // This line still errors jclass clazz = env->FindClass("com/prndl/project/WebExecute"); jmethodID method = env->GetMethodID(clazz, "website", "(Ljava/lang/String;)V"); env->CallVoidMethod(NULL,method); vm->DestroyJavaVM(); And this is the JAVA Method that I need to call: public class WebExecute extends Activity{ public void website(){ Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.com")); startActivity(browserIntent); } } Honestly, I am struggling with this, any help is appreciated. Thanks.

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  • iPhone - NSURLConnection does not receive data

    - by Jukurrpa
    Hi, I have a pretty weird problem with NSURLRequest. I'm using them to make an asynchronous image loading in an UITableView. The first time the tableView displays, all connections from NSURLRequests open correctly but receive absolutely no data, regardless of how long I wait. But as soon as I scroll down in the tableView, the newly created requests for the new cells work perfectly! The only way for the images on top of the tableView to load is to make them disappear by scrolling down and then up again, in order to create new requests. Here is what I do in "cellForRowAtIndexPath": UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"]; if (cell == nil) { cell = [[UITableViewCell alloc] initWIthFrame:CGRectMake(0, 0, 300, 60)]; AsyncUIImageView imageView = [[AsynUIImageView alloc] initWithFrame:CGRectMake(0, 0, 60, 60)]; imageView.tag = IMG_VIEW // an enum for tags [cell addSubView:imageView]; [imageView release]; } AsyncUIImageView imageView = (AsyncUIImageView*)[cell viewWithTag:IMG_VIEW]; // I do a few cache checks here, but if the image aint cached I do this: [imageView loadImageFromURL:@"http://someurl.com/somepix.jpg"]; // all urls are different, just an example The AsyncUIImageView inherits from UIImageView and contains an NSURLConnection which opens upon calling the loadImageFromURL method: (void) loadImageFromURL:(NSString*)filename { if (self.connection != nil) [self.connection release]; if (self.data != nil) [self.data release]; NSURLRequest* request = [NSURLRequest requestWithURL:[[NSURL alloc] initWithString:fileName] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0]; self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; if (self.connection == nil) return; self.data = [[NSMutableData data] retain]; } I've created the delegate methods "connection: didReceiveData", which appends received data to self.data and "connectionDidFinishLoading" which sets the image and closes the connection once the transfer is complete. These work, but are never called for the first requests I create. I suspect this bug to come from the main thread not giving the first requests the control so they can execute themselves, as the same behavior happens if I keep my finger on the screen after a scroll: connections open themselves, but no data is received until I stop touching the screen. What am I doing wrong?

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  • Store Observer not being called always

    - by Nixarn
    Has anyone else here experienced problems with their Store Observer class not being called always when the user for instance cancels a request (or purchases something) We just had our update that brought in app purchases go live last night, and before that we had obviously tested everything tons of times against the Sandbox and everything was working fine. Now however, when the update went live in a real environment we keep getting issues with the store. For instance, in a freshly booted iPhone / iPod, the first time you run the app, if you then try to make a purchase and then immediately cancel it from the first dialog, it seems as if the callback for the cancel is not getting called. If you then restart the app it seems as if it always works after that, or at least. Same thing with other callbacks, seems as if our store observer isn't listening as the callbacks aren't being registered on the phone. One example of this is if you purchase something, then nothing will happen (if this is the first time the app is launched at least). You get the purchase successful dialog from the app store but it seems as if our own code isn't called. If you then quit the app and restart it the callback gets called. Same problem happens if you for instance try to start a request to download all previous purchases and then immediately cancel it as the first dialog pops up, if you do that then the callback for a failed restore is not called, until you then restart the app and try it again, then it always seems to work. The way we have implemented our store observer is by creating a custom class that's implements the SKPaymentTransactionObserver interface. @interface StoreObserver : NSObject<SKPaymentTransactionObserver> In the class we have implemented the following methods: - (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)transactions - (void)paymentQueueRestoreCompletedTransactionsFinished:(SKPaymentQueue *)queue - (void)paymentQueue:(SKPaymentQueue *)queue restoreCompletedTransactionsFailedWithError:(NSError *)error The way our restore process works is that if you tap on the button that allows you to download all we simply run the restoreCompletedTransactions code as follows: [[SKPaymentQueue defaultQueue] restoreCompletedTransactions]; However, the callback, restoreCompletedTransactionsFailedWithError, which has been implemented in the store observer, does not always get called when we try to cancel the request. This happens when you boot the iPhone / iPod and try this for the first time. If you after that restart the app everything works fine. The StoreObserver class is created when our app is launched, just by running the following code: pStoreObserver = [[StoreObserver alloc] init]; [[SKPaymentQueue defaultQueue] addTransactionObserver:pStoreObserver]; Has anyone else had any similar experiences? Or does anyone have any suggestions on how to solve this? As I said, in the sandbox environment everything was working fine, no issues whatsoever, but now once it's gone live we're experiencing these.

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  • Defined variables and arrays vs functions in php

    - by Frank Presencia Fandos
    Introduction I have some sort of values that I might want to access several times each page is loaded. I can take two different approaches for accessing them but I'm not sure which one is 'better'. Three already implemented examples are several options for the Language, URI and displaying text that I describe here: Language Right now it is configured in this way: lang() is a function that returns different values depending on the argument. Example: lang("full") returns the current language, "English", while lang() returns the abbreviation of the current language, "en". There are many more options, like lang("select"), lang("selectact"), etc that return different things. The code is too long and irrelevant for the case so if anyone wants it just ask for it. Url The $Url array also returns different values depending on the request. The whole array is fully defined in the beginning of the page and used to get shorter but accurate links of the current page. Example: $Url['full'] would return "http://mypage.org/path/to/file.php?page=1" and $Url['file'] would return "file.php". It's useful for action="" within the forms and many other things. There are more values for $Url['folder'], $Url['file'], etc. Same thing about the code, if wanted, just request it. Text [You can skip this section] There's another array called $Text that is defined in the same way than $Url. The whole array is defined at the beginning, making a mysql call and defining all $Text[$i] for current page with a while loop. I'm not sure if this is more efficient than multiple calls for a single mysql cell. Example: $Text['54'] returns "This is just a test array!" which this could perfectly be implemented with a function like text(54). Question With the 3 examples you can see that I use different methods to do almost the same function (no pun intended), but I'm not sure which one should become the standard one for my code. I could create a function called url() and other called text() to output what I want. I think that working with functions in those cases is better, but I'm not sure why. So I'd really appreciate your opinions and advice. Should I mix arrays and functions in the way I described or should I just use funcions? Please, base your answer in this: The source needs to be readable and reusable by other developers Resource consumption (processing, time and memory). The shorter the code the better. The more you explain the reasons the better. Thank you PS, now I know the differences between $Url and $Uri.

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  • SwingWorker exceptions lost even when using wrapper classes

    - by Ti Strga
    I've been struggling with the usability problem of SwingWorker eating any exceptions thrown in the background task, for example, described on this SO thread. That thread gives a nice description of the problem, but doesn't discuss recovering the original exception. The applet I've been handed needs to propagate the exception upwards. But I haven't been able to even catch it. I'm using the SimpleSwingWorker wrapper class from this blog entry specifically to try and address this issue. It's a fairly small class but I'll repost it at the end here just for reference. The calling code looks broadly like try { // lots of code here to prepare data, finishing with SpecialDataHelper helper = new SpecialDataHelper(...stuff...); helper.execute(); } catch (Throwable e) { // used "Throwable" here in desperation to try and get // anything at all to match, including unchecked exceptions // // no luck, this code is never ever used :-( } The wrappers: class SpecialDataHelper extends SimpleSwingWorker { public SpecialDataHelper (SpecialData sd) { this.stuff = etc etc etc; } public Void doInBackground() throws Exception { OurCodeThatThrowsACheckedException(this.stuff); return null; } protected void done() { // called only when successful // never reached if there's an error } } The feature of SimpleSwingWorker is that the actual SwingWorker's done()/get() methods are automatically called. This, in theory, rethrows any exceptions that happened in the background. In practice, nothing is ever caught, and I don't even know why. The SimpleSwingWorker class, for reference, and with nothing elided for brevity: import java.util.concurrent.ExecutionException; import javax.swing.SwingWorker; /** * A drop-in replacement for SwingWorker<Void,Void> but will not silently * swallow exceptions during background execution. * * Taken from http://jonathangiles.net/blog/?p=341 with thanks. */ public abstract class SimpleSwingWorker { private final SwingWorker<Void,Void> worker = new SwingWorker<Void,Void>() { @Override protected Void doInBackground() throws Exception { SimpleSwingWorker.this.doInBackground(); return null; } @Override protected void done() { // Exceptions are lost unless get() is called on the // originating thread. We do so here. try { get(); } catch (final InterruptedException ex) { throw new RuntimeException(ex); } catch (final ExecutionException ex) { throw new RuntimeException(ex.getCause()); } SimpleSwingWorker.this.done(); } }; public SimpleSwingWorker() {} protected abstract Void doInBackground() throws Exception; protected abstract void done(); public void execute() { worker.execute(); } }

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  • Overfocus in GridView

    - by chuck258
    I'm trying to implement a GridView that Focuses the next Item and "Overscrolls at the End of a List. E.g. 1 2 3 4 5 6 7 8 9 I want to scroll 1 2 3 4 5 6 ... just by pressing the right Key. Right now I can only Scroll 1 2 3 and then it stops and I have to scroll with the down Key. I already tried to set the focusViews in code (In the getView() method of my ArrayList Adapter, that fills the GridView) view.setId(position); view.setNextFocusLeftId(position-1); view.setNextFocusRightId(position+1); But that doesn't work. I found the boolean *Scroll(int direction) Methods on grepcode But theese are Package Local and I can't overwrite them. Any suggestions on how to solve this. Can I use another View and get the same Layout as a Gridview? I also set a OnFocusChangeListener to see what happens with no reaction. Edit: I just added this to my MainActivity, but now it seems to onKeyDown only get called when the GridView doesn't handle the KeyEvent (If the Last Item in a row is selected). @Override public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_DPAD_LEFT: if (focusedView > 0) { mContainer.setSelection(--focusedView); Log.v("TEST", focusedView+""); } return true; case KeyEvent.KEYCODE_DPAD_RIGHT: if (focusedView < mAdapter.getCount() - 1) { mContainer.setSelection(++focusedView); Log.v("TEST", focusedView+""); } return true; } return super.onKeyDown(keyCode, event); } Edit 2: This is so f***ing stupid but works so damn fine :D @Override public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_DPAD_LEFT: mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_UP, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_UP)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_RIGHT)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_RIGHT)); return true; case KeyEvent.KEYCODE_DPAD_RIGHT: mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_DOWN, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_DOWN)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_LEFT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_LEFT)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_LEFT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_LEFT)); return true; } return super.onKeyDown(keyCode, event); } I really don't want to post this as Answer, and I really don't want to have to use this Code because it is such a stupid workaround ;TLDR: Help still needed

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  • C++ exam question on string class implementation

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • iOS dynamic object creation

    - by Abdul Ahmad
    I've worked with Xcode and iOS on a few personal projects and have always used non-object-oriented designs for everything... just because I've been doing mostly learning/experimenting with things. Now I've been trying to implement some object oriented design into one game I've made previously. The idea is, I have a space ship that can shoot bullets. In the past I basically added the UIImageView to the storyboard and then connected it to the .h file and from there did things on it like move it around or whatever (using CGPointMake). The idea now is to make a method (and a whole other class soon) that will create a UIImageView programmatically, allocate it, add it to the superview etc... I've got this working so far, easy stuff, but the next part is a bit harder. Where do I store this local variable "bullet"? I've been saving it to an NSMutableArray and doing the following: (actually here are the methods that I have) -(void)movement { for (int i = 0; i < [array1 count]; i ++) { UIImageView *a = [array1 objectAtIndex:i]; a.center = CGPointMake(a.center.x + 2, a.center.y); if (a.center.x > 500) { [array1 removeObjectAtIndex:i]; [a removeFromSuperview]; } } } -(void)getBullet { UIImageView *bullet = [[UIImageView alloc] initWithFrame:CGRectMake(ship.center.x + 20, ship.center.y - 2, 15, 3)]; bullet.image = [UIImage imageNamed:@"bullet2.png"]; bullet.hidden = NO; [self.view addSubview:bullet]; [array1 addObject:bullet]; } (by the way, array1 is declared in the .h file) and theres a timer that controls the movement method timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(movement) userInfo:nil repeats:YES]; first question is: what is the correct way of doing this? Storing a bullet for example until it is removed from the superview, should I store it another way? and another question is, when I remove a UIImageView from the superview, does that remove it from memory so its not using up system resources? Thank you for the help! (will update if I Think of other questions

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  • Is it any loose coupling mechanism in Objective-C + Cocoa like C# delegates or C++Qt signals+slots?

    - by Eye of Hell
    Hello. For a large programs, the standard way to chalenge a complexity is to divide a program code into small objects. Most of the actual programming languages offer this functionality via classes, so is Objective-C. But after source code is separated into small object, the second challenge is to somehow connect them with each over. Standard approaches, supported by most languages are compositon (one object is a member field of another), inheritance, templates (generics) and callbacks. More cryptic techniques include method-level delagates (C#) and signals+slots (C++Qt). I like the delegates / signals idea, since while connecting two objects i can connect individual methods with each over, without objects knowing anything of each over. For C#, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); object1.SomethingHappened += object2.HandleSomething; In this code, is object1 calls it's SomethingHappened delegate (like a normal method call) the HandleSomething method of object2 will be called. For C++Qt, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); connect( object1, SIGNAL(SomethingHappened()), object2, SLOT(HandleSomething()) ); The result will be exactly the same. This technique has some advantages and disadvantages, but generally i like it more than interfaces since if program code base grows i can change connections and add new ones without creating tons of interfaces. After examination of Objective-C i havn't found any way to use this technique i like :(. It seems that Objective-C supports message passing perfectly well, but it requres for object1 to have a pointer to object2 in order to pass it a message. If some object needs to be connected to lots of other objects, in Objective-C i will be forced to give him pointers to each of the objects it must be connected. So, the question :). Is it any approach in Objective-C programming that will closely resemble delegate / signal+slot types of connection, not a 'give first object an entire pointer to second object so it can pass a message to it'. Method-level connections are a bit more preferable to me than object-level connection ^_^.

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  • Web Services, Memory Leaks and CRM

    - by Neil
    Hi, I have a website that allows users to upload a csv file. This calls a service that reads the information from the csv, puts it into DynamicEntity objects and calls the CRM service to Create/Update entities in CRM. When this service creates/updates an entity this kicks off other plugins to apply certain business rules. These rules can also Create or Update entites in CRM. The issue here is that the handle count of the w3wp.exe process that the website is calling increases every time the an entity is created or updated and it never comes back down. I tried putting Garbage Collection code in the business rules and this reduces the handle count of the CRM w3wp process (run by the Network Service), but not the other w3wp process. Should I have Dispose methods on the Web Service that calls the CRM service? I hope that makes sense. I'm not overly familiar with memory management issues so any help is appreciated. Can anybody give me some tips on how to stop this from occurring? Thanks, Neil -- EDIT Okay well the handle count goes up when I call the Service.Create(DynamicEntity) method. I don't think placing any code here would be beneficial. When I exit the method/class/service that contains this call the handle count stays as it is. What I need to know is whether this is something I should be managing or is it something CRM takes care of (or doesn't take care of but I can't do anything about it) -- Another Edit Right this is how it works. 1) We have CRM and its related services 2) We have another service independent of CRM that uses the CRM services (number 1 above) to create entities based on csv info passed into it 3) We have a website that allows a user to upload a csv, and calls service no 2 above to Create/Update entities in CRM 4) We have plugins fired by CRM which use Service 1 above to create/update entities So the user uploads a csv to the website (3), this fires a service(2). When service 2 creates an entity using service 1, Service 4 fires. Service 4 calls also uses service 1 to Create entities, and when these services are called (using the Service.Create() method) the handle count of the process increases. When the method/class/services finish the handle count remains the same, and so when the whole process occurs again the handle count will increased again.

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  • Router Alert options on IGMPv2 packets

    - by Scakko
    I'm trying to forge an IGMPv2 Membership Request packet and send it on a RAW socket. The RFC 3376 states: IGMP messages are encapsulated in IPv4 datagrams, with an IP protocol number of 2. Every IGMP message described in this document is sent with an IP Time-to-Live of 1, IP Precedence of Internetwork Control (e.g., Type of Service 0xc0), and carries an IP Router Alert option [RFC-2113] in its IP header So the IP_ROUTER_ALERT flag must be set. I'm trying to forge the strict necessary of the packet (e.g. only the IGMP header & payload), so i'm using the setsockopt to edit the IP options. some useful variables: #define C_IP_MULTICAST_TTL 1 #define C_IP_ROUTER_ALERT 1 int sockfd = 0; int ecsockopt = 0; int bytes_num = 0; int ip_multicast_ttl = C_IP_MULTICAST_TTL; int ip_router_alert = C_IP_ROUTER_ALERT; Here's how I open the RAW socket: sock_domain = AF_INET; sock_type = SOCK_RAW; sock_proto = IPPROTO_IGMP; if ((ecsockopt = socket(sock_domain,sock_type,sock_proto)) < 0) { printf("Error %d: Can't open socket.\n", errno); return 1; } else { printf("** Socket opened.\n"); } sockfd = ecsockopt; Then I set the TTL and Router Alert option: // Set the sent packets TTL if((ecsockopt = setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ip_multicast_ttl, sizeof(ip_multicast_ttl))) < 0) { printf("Error %d: Can't set TTL.\n", ecsockopt); return 1; } else { printf("** TTL set.\n"); } // Set the Router Alert if((ecsockopt = setsockopt(sockfd, IPPROTO_IP, IP_ROUTER_ALERT, &ip_router_alert, sizeof(ip_router_alert))) < 0) { printf("Error %d: Can't set Router Alert.\n", ecsockopt); return 1; } else { printf("** Router Alert set.\n"); } The setsockopt of IP_ROUTER_ALERT returns 0. After forging the packet, i send it with sendto in this way: // Send the packet if((bytes_num = sendto(sockfd, packet, packet_size, 0, (struct sockaddr*) &mgroup1_addr, sizeof(mgroup1_addr))) < 0) { printf("Error %d: Can't send Membership report message.\n", bytes_num); return 1; } else { printf("** Membership report message sent. (bytes=%d)\n",bytes_num); } The packet is sent, but the IP_ROUTER_ALERT option (checked with wireshark) is missing. Am i doing something wrong? is there some other methods to set the IP_ROUTER_ALERT option? Thanks in advance.

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  • c++ property class structure

    - by Without me Its just Aweso
    I have a c++ project being developed in QT. The problem I'm running in to is I am wanting to have a single base class that all my property classes inherit from so that I can store them all together. Right now I have: class AbstractProperty { public: AbstractProperty(QString propertyName); virtual QString toString() const = 0; virtual QString getName() = 0; virtual void fromString(QString str) = 0; virtual int toInteger() = 0; virtual bool operator==(const AbstractProperty &rightHand) = 0; virtual bool operator!=(const AbstractProperty &rightHand) = 0; virtual bool operator<(const AbstractProperty &rightHand) = 0; virtual bool operator>(const AbstractProperty &rightHand) = 0; virtual bool operator>=(const AbstractProperty &rightHand) = 0; virtual bool operator<=(const AbstractProperty &rightHand) = 0; protected: QString name; }; then I am implementing classes such as PropertyFloat and PropertyString and providing implementation for the comparator operators based on the assumption that only strings are being compared with strings and so on. However the problem with this is there would be no compiletime error thrown if i did if(propertyfloat a < propertystring b) however my implementation of the operators for each derived class relies on them both being the same derived class. So my problem is I cant figure out how to implement a property structure so that I can have them all inherit from some base type but code like what I have above would throw a compile time error. Any ideas on how this can be done? For those familiar with QT I tried using also a implementation with QVariant however QVariant doesn't have operators < and defined in itself only in some of its derived classes so it didn't work out. What my end goal is, is to be able to generically refer to properties. I have an element class that holds a hashmap of properties with string 'name' as key and the AbstractProperty as value. I want to be able to generically operate on the properties. i.e. if I want to get the max and min values of a property given its string name I have methods that are completely generic that will pull out the associated AbstactProperty from each element and find the max/min no matter what the type is. so properties although initially declared as PropertyFloat/PropertyString they will be held generically.

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  • Can I use the [] operator in C++ to create virtual arrays

    - by Shane MacLaughlin
    I have a large code base, originally C ported to C++ many years ago, that is operating on a number of large arrays of spatial data. These arrays contain structs representing point and triangle entities that represent surface models. I need to refactor the code such that the specific way these entities are stored internally varies for specific scenarios. For example if the points lie on a regular flat grid, I don't need to store the X and Y coordinates, as they can be calculated on the fly, as can the triangles. Similarly, I want to take advantage of out of core tools such as STXXL for storage. The simplest way of doing this is replacing array access with put and get type functions, e.g. point[i].x = XV; becomes Point p = GetPoint(i); p.x = XV; PutPoint(i,p); As you can imagine, this is a very tedious refactor on a large code base, prone to all sorts of errors en route. What I'd like to do is write a class that mimics the array by overloading the [] operator. As the arrays already live on the heap, and move around with reallocs, the code already assumes that references into the array such as point *p = point + i; may not be used. Is this class feasible to write? For example writing the methods below in terms of the [] operator; void MyClass::PutPoint(int Index, Point p) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); StoreGridPoint(xoffs,yoffs,p.z); } else m_PointArray[Index] = p; } } Point MyClass::GetPoint(int Index) { if (m_StorageStrategy == RegularGrid) { int xoffs,yoffs; ComputeGridFromIndex(Index,xoffs,yoffs); return GetGridPoint(xoffs,yoffs); // GetGridPoint returns Point } else return m_PointArray[Index]; } } My concern is that all the array classes I've seen tend to pass by reference, whereas I think I'll have to pass structs by value. I think it should work put other than performance, can anyone see any major pitfalls with this approach. n.b. the reason I have to pass by value is to get point[a].z = point[b].z + point[c].z to work correctly where the underlying storage type varies.

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  • When does logic belong in the Business Object/Entity, and when does it belong in a Service?

    - by Casey
    In trying to understand Domain Driven Design I keep returning to a question that I can't seem to definitively answer. How do you determine what logic belongs to a Domain entity, and what logic belongs to a Domain Service? Example: We have an Order class for an online store. This class is an entity and an aggregate root (it contains OrderItems). Public Class Order:IOrder { Private List<IOrderItem> OrderItems Public Order(List<IOrderItem>) { OrderItems = List<IOrderItem> } Public Decimal CalculateTotalItemWeight() //This logic seems to belong in the entity. { Decimal TotalWeight = 0 foreach(IOrderItem OrderItem in OrderItems) { TotalWeight += OrderItem.Weight } return TotalWeight } } I think most people would agree that CalculateTotalItemWeight belongs on the entity. However, at some point we have to ship this order to the customer. To accomplish this we need to do two things: 1) Determine the postage rate necessary to ship this order. 2) Print a shipping label after determining the postage rate. Both of these actions will require dependencies that are outside the Order entity, such as an external webservice to retrieve postage rates. How should we accomplish these two things? I see a few options: 1) Code the logic directly in the domain entity, like CalculateTotalItemWeight. We then call: Order.GetPostageRate Order.PrintLabel 2) Put the logic in a service that accepts IOrder. We then call: PostageService.GetPostageRate(Order) PrintService.PrintLabel(Order) 3) Create a class for each action that operates on an Order, and pass an instance of that class to the Order through Constructor Injection (this is a variation of option 1 but allows reuse of the RateRetriever and LabelPrinter classes): Public Class Order:IOrder { Private List<IOrderItem> OrderItems Private RateRetriever _Retriever Private LabelPrinter _Printer Public Order(List<IOrderItem>, RateRetriever Retriever, LabelPrinter Printer) { OrderItems = List<IOrderItem> _Retriever = Retriever _Printer = Printer } Public Decimal GetPostageRate { _Retriever.GetPostageRate(this) } Public void PrintLabel { _Printer.PrintLabel(this) } } Which one of these methods do you choose for this logic, if any? What is the reasoning behind your choice? Most importantly, is there a set of guidelines that led you to your choice?

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