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  • Does delegate chaining have to start with a null Delegate?

    - by MCS
    In CLR via C#, Jeffrey Richter gives the following example of delegate chaining (pg. 406): internal delegate void Feedback(Int 32 value); Feedback fb1 = new Feedback(method1); // in the book, these methods Feedback fb2 = new Feedback(method2); // have different names Feedback fb3 = new Feedback(method3); Feedback fbChain = null; fbChain = (Feedback) Delegate.Combine(fbChain, fb1); fbChain = (Feedback) Delegate.Combine(fbChain, fb2); fbChain = (Feedback) Delegate.Combine(fbChain, fb3); Why does the first call to Delegate.Combine have to pass in a null Delegate? Here's how I would have thought it should be written: Feedback fbChain = (Feedback) Delegate.Combine(fb1, fb2); fbChain = (Feedback) Delegate.Combine(fbchain, fb3);

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  • Best way to check for null values in Java?

    - by Arty-fishL
    I need to check whether the function of an object returns true or false in Java, but that object may be null, so obviously then the function would throw a NullPointerException. This means I need to check if the object is null before checking the value of the function. What is the best way to go about this? I've listed some methods I considered, I just want to know the most sensible one, the one that is best programming practice for Java (opinion?). // method 1 if (foo != null) { if (foo.bar()) { etc... } } // method 2 if (foo != null ? foo.bar() : false) { etc... } // method 3 try { if (foo.bar()) { etc... } } catch (NullPointerException e) { } // method 4 // would this work all the time, would it still call foo.bar()? if (foo != null && foo.bar()) { etc... }

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  • ActiveX communication

    - by Mario Marinato -br-
    I'm developing an ActiveX EXE that exposes an specific class to a third-party software. This third-party software instanciates an object of this class and uses its methods. Strangely, this third-party software destroys its object of my exposed class as soon as it calls an specific method, but I have no idea why this happens. The only clue I have is that this method is the only one that returns a value. All the other ones are simple 'subs' that do not return any value, and when they are called nothing wrong happens. I'm using VB6. Do you guys have any idea of why it's happening?

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  • Better to use constructor or method factory pattern?

    - by devoured elysium
    I have a wrapper class for the Bitmap .NET class called BitmapZone. Assuming we have a WIDTH x HEIGHT bitmap picture, this wrapper class should serve the purpose of allowing me to send to other methods/classes itself instead of the original bitmap. I can then better control what the user is or not allowed to do with the picture (and I don't have to copy the bitmap lots of times to send for each method/class). My question is: knowing that all BitmapZone's are created from a Bitmap, what do you find preferrable? Constructor syntax: something like BitmapZone bitmapZone = new BitmapZone(originalBitmap, x, y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.From(originalBitmap, x , y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.FromBitmap(originalBitmap, x, y, width, height); Other? Why? Thanks

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  • Objects in interface

    - by Peter Kowalchuk
    I created my own object, PKSurvey. In the interface of the View Controller I can define a pointer to it, then in a method I can alloc it and have an instance. How do I keep the instance beyond the method where it was allocated? I assign values in one method and want to be able to use those values in other methods. Should I allocate it in the viewDidLoad method or should I do it somewhere else? @interface DIrectionalDrillerViewController : UIViewController { PKSurvey *Survey=[PKSurvey new]; ---------------- - (void)viewDidLoad { [Survey new];

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  • How do I throttle my site's API users?

    - by scotts
    The legitimate users of my site occasionally hammer the server with API requests that cause undesirable results. I want to institute a limit of no more than say one API call every 5 seconds or n calls per minute (haven't figured out the exact limit yet). I could obviously log every API call in a DB and do the calculation on every request to see if they're over the limit, but all this extra overhead on EVERY request would be defeating the purpose. What are other less resource-intensive methods I could use to institute a limit? I'm using PHP/Apache/Linux, for what it's worth.

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  • delete in tableView..

    - by totato
    I just add this methods in .h file : - (IBAction)EditTable:(id)sender; - (IBAction)DeleteButtonAction:(id)sender; and in .m file : (IBAction)DeleteButtonAction:(id)sender{ [tableList removeLastObject]; [Table reloadData]; } (IBAction) EditTable:(id)sender{ if(self.editing) { [super setEditing:NO animated:NO]; [Table setEditing:NO animated:NO]; [Table reloadData]; [self.navigationItem.leftBarButtonItem setTitle:@"Edit"]; [self.navigationItem.leftBarButtonItem setStyle:UIBarButtonItemStylePlain]; } else { [super setEditing:YES animated:YES]; [Table setEditing:YES animated:YES]; [Table reloadData]; [self.navigationItem.leftBarButtonItem setTitle:@"Done"]; [self.navigationItem.leftBarButtonItem setStyle:UIBarButtonItemStyleDone]; } } when I run the program and click the delete button (red button) the program is stop ! whats the problem ? please any help ?

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  • How does multiple implementing multiple COM interfaces work in C++?

    - by Martin
    I am trying to understand this example code regarding Browser Helper Objects. Inside, the author implements a single class which exposes multiple interfaces (IObjectWithSite, IDispatch). His QueryInterface function performs the following: if(riid == IID_IUnknown) *ppv = static_cast<BHO*>(this); else if(riid == IID_IObjectWithSite) *ppv = static_cast<IObjectWithSite*>(this); else if (riid == IID_IDispatch) *ppv = static_cast<IDispatch*>(this); I have learned that from a C perspective, interface pointers are just pointers to VTables. So I take it to mean that C++ is capable of returning the VTable of any implemented interface using static_cast. Does this mean that a class constructed in this way has a bunch of VTables in memory (IObjectWithSite, IDispatch, etc)? What does C++ do with the name collisions on the different interfaces (they each have a QueryInterface, AddRef and Release function), can I implement different methods for each of these?

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  • Android: who can help me with setting up this google maps class please??

    - by Capsud
    Hi, Firstly this has turned out to be quite a long post so please bear with me as its not too difficult but you may need to clarify something with me if i haven't explained it correctly. So with some help the other day from guys on this forum, i managed to partially set up my 'mapClass' class, but i'm having trouble with it and its not running correctly so i would like some help if possible. I will post the code below so you can see. What Ive got is a 'Dundrum' class which sets up the listView for an array of items. Then ive got a 'dundrumSelector' class which I use to set up the setOnClickListener() methods on the listItems and link them to their correct views. DundrumSelector class.. public static final int BUTTON1 = R.id.anandaAddressButton; public static final int BUTTON2 = R.id.bramblesCafeAddressButton; public static final int BUTTON3 = R.id.brannigansAddressButton; public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); int position = getIntent().getExtras().getInt("position"); if(position == 0){ setContentView(R.layout.ananda); }; if(position == 1){ setContentView(R.layout.bramblescafe); }; if(position == 2){ setContentView(R.layout.brannigans); Button anandabutton = (Button) findViewById(R.id.anandaAddressButton); anandabutton.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { Intent myIntent = new Intent(view.getContext(),MapClass.class); myIntent.putExtra("button", BUTTON1); startActivityForResult(myIntent,0); } }); Button bramblesbutton = (Button) findViewById(R.id.bramblesCafeAddressButton); bramblesbutton.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { Intent myIntent = new Intent(view.getContext(),MapClass.class); myIntent.putExtra("button", BUTTON2); startActivityForResult(myIntent, 0); } }); etc etc.... Then what i did was set up static ints to represent the buttons which you can see at the top of this class, the reason for this is because in my mapClass activity I just want to have one method, because the only thing that is varying is the coordinates to each location. ie. i dont want to have 100+ map classes essentially doing the same thing other than different coordinates into the method. So my map class is as follows... case DundrumSelector.BUTTON1: handleCoordinates("53.288719","-6.241179"); break; case DundrumSelector.BUTTON2: handleCoordinates("53.288719","-6.241179"); break; case DundrumSelector.BUTTON3: handleCoordinates("53.288719","-6.241179"); break; } } private void handleCoordinates(String l, String b){ mapView = (MapView) findViewById(R.id.mapView); LinearLayout zoomLayout = (LinearLayout)findViewById(R.id.zoom); View zoomView = mapView.getZoomControls(); zoomLayout.addView(zoomView, new LinearLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); mapView.displayZoomControls(true); mc = mapView.getController(); String coordinates[] = {l, b}; double lat = Double.parseDouble(coordinates[0]); double lng = Double.parseDouble(coordinates[1]); p = new GeoPoint( (int) (lat*1E6), (int) (lng*1E6)); mc.animateTo(p); mc.setZoom(17); mapView.invalidate(); } Now this is where my problem is. The onClick() events don't even work from the listView to get into the correct views. I have to comment out the methods in 'DundrumSelector' before I can get into their views. And this is what I dont understand, firstly why wont the onClick() events work, because its not even on that next view where the map is. I know this is a very long post and it might be quite confusing so let me know if you want any clarification.. Just to recap, what i'm trying to do is just have one class that sets up the map coordinates, like what i'm trying to do in my 'mapClass'. Please can someone help or suggest another way of doing this! Thanks alot everyone for reading this.

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  • How to check function parameters in Go

    - by deamon
    Guava Preconditions allows to check method parameters in Java easily. public void doUsefulThings(Something s, int x, int position) { checkNotNull(s); checkArgument(x >= 0, "Argument was %s but expected nonnegative", x); checkElementIndex(position, someList.size()); // ... } These check methods raise exceptions if the conditions are not met. Go has no exceptions but indicates errors with return values. So I wonder how an idiomatic Go version of the above code would look like.

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  • testing .mobile mime format with capybara / rspec

    - by Chris Beck
    For detecting and responding to mobile user agents, I'm using Mime::Type.register_alias "text/html", :mobile and the approach I'm wondering what is the best approach to test with capybara. This article suggests setting up an iphone driver with Capybara.register_driver :iphone do |app| http://blog.plataformatec.com.br/2011/03/configuring-user-agents-with-capybara-selenium-webdriver/ but I'd like a more flexible approach where the mime type is set via the url extension localhost/index.mobile and where I can do this visit user_path( format: :mobile) Rails understands the extension and sets the format in the params hash, but how do I get the url helper methods to add that to all urls as a file extension?

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  • What is a flexible, hybrid python collection object?

    - by Naveen
    As a way to get used to python, I am trying to translate some of my code to python from Autohotkey_L. I am immediately running into tons of choices for collection objects. Can you help me figure out a built in type or a 3rd party contributed type that has as much as possible, the functionality of the AutoHotkey_L object type and its methods. AutoHotkey_L Objects have features of a python dict, list, and a class instance. I understand that there are tradeoffs for space and speed, but I am just interested in functionality rather than optimization issues.

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  • How to set Chrome's user script version number.

    - by Atli
    Hey. I've been wondering how I might set the version number displayed for user-scripts in Chrome's extension tab So far the obvious methods have failed: // ==UserScript== // @version 1.1.5 // @uso:version 1.1.5 // ==/UserScript== I know Greasemonkey for Firefox doesn't use a version value, but since Chrome actually displays a version number, I thought it might. Perhaps this is a feature that has not been implemented? Or maybe it was never intended to be there, but it is there because extensions have version numbers, and user-scripts are currently installed as extensions? (I'm using the Linux beta, version: 4.0.249.43, by the way) Thanks. Edit: Seems this is listed as an unconfirmed bug in the Chromium bug database (Issue 30760)

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  • abstract class MouseAdapter vs. interface

    - by Stefano Borini
    I noted this (it's a java.awt.event class). public abstract class MouseAdapter implements MouseListener, MouseWheelListener, MouseMotionListener { .... } Then you are clearly forced to extend from this adapter public class MouseAdapterImpl extends MouseAdapter {} the class is abstract and implements no methods. Is this a strategy to combine different interfaces into a single "basically interface" ? I assume in java it's not possible to combine different interfaces into a single one without using this approach. In other words, it's not possible to do something like this in java public interface MouseAdapterIface extends MouseListener, MouseWheelListener, MouseMotionListener { } and then eventually public class MouseAdapterImpl implements MouseAdapterIface {} Is my understanding of the point correct ? what about C# ?

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  • Stack trace for C++ using gcc

    - by dimba
    We use stack traces in proprietary assert like macro to catch developer mistakes - when error is caught, stack trace is printed. I find gcc's pair backtrace()/backtrace_symbols() methods insufficient: Names are mangled No line information 1st problem can be resolved by abi::__cxa_demangle. However 2nd problem s more tough. I found replacement for backtrace_symbols(). This is better than gcc's backtrace_symbols(), since it can retrieve line numbers (if compiled with -g) and you don't need to compile with -rdynamic. Hoverer the code is GNU licenced, so IMHO I can't use it in commercial code. Any proposals?

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  • javascript: execute a bunch of asynchronous method with one callback

    - by Samuel Michelot
    I need to execute a bunch of asynchronous methods (client SQLite database), and call only one final callback. Of course, the ugly way is: execAll : function(callBack) { asynch1(function() { asynch2(function() { ... asynchN(function() { callBack(); }) }) }); } But I know there are better ways to do it. Intuitively I would detect when all call back has been called with a counter to call the final callback. I think this is a common design-pattern, so if someone could point me in the right direction... Thanks in advance !

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  • WCF Service method syncronous/async

    - by Rafal
    Hi I have a problem withi calling WCF Service methods vs Silverlight 3. ` private bool usr_OK = false; clientService.CheckUserMailAsync(this.mailTF.Text); if (usr_OK == true) { isValidationOK = true; } else { isValidationOK = false; MessageBox.Show("User already exists.", "User registered succes!", MessageBoxButton.OK); } ` CheckUserMail should change usr_OK parameter. However it runs in other thread and it does not change the usr_OK param before IF block begins. I've tried thread.join byt the application freezed and i do not know what to do else. Please help me...how can i wait for WCF method to return param usr_OK.

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  • Android - Looking for an AOP solution

    - by Serj Lotutovici
    I'm writing an application that on the bottom line uses it's internal API for some manipulations. The problem is that to call any method provided by that class first I (or anybody who uses the API) have to call #prepare() and after that #cleanup(). It all worked fine until the application and the API started to grow. And the risk of not calling one of the supplied methods before or after the API is now to big to be ignored (which makes it a bug risky application). Searching for a solution I found this question. I use Google Guice in my app for other purposes, but Android doesn't support AOP, that's why a use only guice-no_aop-x.jar. So I end-up with two questions: Is there an AOP solution for android to implement the same approach that is shown in the link above? Or may be someone has an idea that will be suitable for my case? Thanks in advice!

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  • General zoom algorithm for drawing program

    - by Steven Sproat
    My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

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  • Twisted - how to create multi protocol process and send the data between the protocols

    - by SpankMe
    Hey, Im trying to write a program that would be listening for data (simple text messages) on some port (say tcp 6666) and then pass them to one or more different protocols - irc, xmpp and so on. I've tried many approaches and digged the Internet, but I cant find easy and working solution for such task. The code I am currently fighting with is here: http://pastebin.com/ri7caXih I would like to know how to from object like: ircf = ircFactory('asdfasdf', '#asdf666') get access to self protocol methods, because this: self.protocol.dupa1(msg) returns error about self not being passed to active protocol object. Or maybe there is other, better, easier and more kosher way to create single reactor with multiple protocols and have actions triggeres when a message arrives on any of them, and then pass that message to other protocols for handling/processing/sending? Any help will be highly appreciated!

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  • java - POST vs JDBC

    - by Dan
    OK so here's the code: import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; public class Main { public static void main(String[] args) { try { URL my_url = new URL("http://www.viralpatel.net/blogs/"); BufferedReader br = new BufferedReader(new InputStreamReader(my_url.openStream())); String strTemp = ""; while(null != (strTemp = br.readLine())){ System.out.println(strTemp); } } catch (Exception ex) { ex.printStackTrace(); } } } Using this method I can use POST and GET methods using PHP scripts. I can then use the PHP scripts to the MySQL database which in turn outputs back to the java applet. Is this possible? (and safer?) Thanks.

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  • Scaffold default files are the best practice?

    - by antpaw
    Hey, i have some experience with MVC. but I'm new to rails. I'm using the scaffold command to generate some default files. The model looks clean and nice, but the controller and the views aren't really dry. The contents of new.html.erb and edit.html.erb are almost the same and the methods new/edit and create/update are doing almost the same thing. In other frameworks i've used only one view for updating and creating new entries and also the same method in my controller by setting the id as an optional parameter. Do they use this structure to keep things RESTful (i have not much of a clue about rest :()? Is it the best practice to use this default stuff for crud?

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  • Best .NET Framework compression class?

    - by Jack
    Hi all Yes, I know GZipStream or DeflateStream is the common ones in .NET Framework which handle compression/decompression. I wish to have compress/decompress functions in my program, but I wish a .NET Framework C# one, not a 3rd party open source. I can't use because of those copyright restrictions in my program. GZipStream and DeflateStream are not so good. for e.g., GZipStream compress a file to 480KB while 7Zip compress the same file to the size of 57KB. Does Microsoft have other good compression methods??? Thanks

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  • Creating many new instances vs reusing them?

    - by Hugo Riley
    I have multiple business entities in VB.NET Windows Forms application. Right now they are instanced on application startup and used when needed. They hold descriptions of business entities and methods for storing and retrieving data. To cut the long story short, they are somewhat heavy objects to construct (they have some internal dictionaries and references to other objects) created and held in one big global variable called "BLogic". Should I refactor this so that each object is created when needed and released when out of scope? Then every event on UI will probably create a few of this objects. Should I strive to minimize creation of new objects or to minimize number of static and global objects? Generally I am trying to minimize the scope of every variable but should I treat this business logic objects specially?

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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