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  • How to implement iterator as an attribute of a class in Java

    - by de3
    Hi, let's say I have this simple MyArray class, with two simple methods: add, delete and an iterator. In the main method we can see how it is supposed to be used: public class MyArray { int start; int end; int[] arr; myIterator it; public MyArray(){ this.start=0; this.end=0; this.arr=new int[500]; it=new myIterator(); } public void add(int el){ this.arr[this.end]=el; this.end++; } public void delete(){ this.arr[this.start]=0; this.start++; } public static void main(String[] args){ MyArray m=new MyArray(); m.add(3); m.add(299); m.add(19); m.add(27); while(m.it.hasNext()){ System.out.println(m.it.next()); } } And then MyIterator should be implemented somehow: import java.util.Iterator; public class myIterator implements Iterator{ @Override public boolean hasNext() { // TODO Auto-generated method stub return false; } @Override public Object next() { // TODO Auto-generated method stub return null; } @Override public void remove() { // TODO Auto-generated method stub } } MyIterator should iterate arr from MyArray class, from start to end values; both are also attributes of MyArray. So, as MyIterator should use MyArray attributes, how should MyIterator be implemented? Perhaps I can send the current object in the initialization: it=new myIterator(this); But I guess it's not the best soultion. Or maybe MyArray itself should implement Iterator interface? How is this solved?

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  • How to view my Android app created database, via my android app?

    - by suufang
    I'm creating an application that collects users location (Cell broadcast location code) and saves that location with a name of users option, for example say my CB location code is 546034, now my app allows me to store that location code with a name of my choice say 'Home'. So, essentially my app has that following modules, To collect users CB location. To collect a custom name from user of that location. To store these values in a database. I've succeeded in doing all the above modules. I have a sub-module for my third module which has an option for user, of showing and deleting the database values, the screen shot looks as follows, Now, Users should be able to view and delete entries when he chooses the option 'View my database of locations' I've learned how to query my database values and I'm stuck with creating a list view and providing the delete option. My code for getting the database values and querying values goes as follows, submit.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { String locname = name.getText().toString(); if(locname.length()==0) { Toast.makeText(getBaseContext(), "Please enter the location name, for example 'Home'.", Toast.LENGTH_LONG).show(); } else { SQLiteDatabase cd = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null); cd.execSQL("CREATE TABLE IF NOT EXISTS MLITable (CblocationCode INT(10), CblocationName VARCHAR);"); cd.execSQL("INSERT INTO MLITable VALUES ('"+str+ "','"+locname+ "');"); cd.close(); Toast.makeText(getBaseContext(), "value successfully entered.", Toast.LENGTH_LONG).show(); } } }); viewdb.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // here comes the code for viewing the database and deleting SQLiteDatabase db = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null); Cursor c = db.rawQuery("SELECT * FROM MLITble", null); db.close(); } }); I can see that I've read the table values, but I'm not able to create a display for those values. Help required. Thank you.

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  • Dealing with image upload on server

    - by user1073320
    I have got a the following problem: I have got multi-step form where in one step user upload image to server and then few steps further supplies other information, when this information is invalid no data should be commited - also the image should be deleted. I was thinking about PHP session, but I've read here PHP - Store Images in SESSION data? that it is inefficient way. Every time you proceed step in the form the image is reloaded (in the session) and as somebody mentioned "You will want it to only be as big as it needs to be and you need to delete it as soon as you don't need it because large pieces of information in the session will slow down the session startup." - here i got a question: will it slow down the stratup the session of user who upload file or sessions of all users? I have to mention that I'm looking for solution that doesn't rely on operating system scripts (cron or etc) - I have no permission to run such scripts. The perfect solution for me would be: saving image on disk (for example in some folder named after session id) then after the latest step of form move this image or delete depending on form validation. If user unexpectedly destroy the session (for example closing the browser) of course the folder with image should be deleted. In nutshell I need somethig like callback to event "destroying session".

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  • Implementing a non-public assignment operator with a public named method?

    - by Casey
    It is supposed to copy an AnimatedSprite. I'm having second thoughts that it has the unfortunate side effect of changing the *this object. How would I implement this feature without the side effect? EDIT: Based on new answers, the question should really be: How do I implement a non-public assignment operator with a public named method without side effects? (Changed title as such). public: AnimatedSprite& AnimatedSprite::Clone(const AnimatedSprite& animatedSprite) { return (*this = animatedSprite); } protected: AnimatedSprite& AnimatedSprite::operator=(const AnimatedSprite& rhs) { if(this == &rhs) return *this; destroy_bitmap(this->_frameImage); this->_frameImage = create_bitmap(rhs._frameImage->w, rhs._frameImage->h); clear_bitmap(this->_frameImage); this->_frameDimensions = rhs._frameDimensions; this->CalcCenterFrame(); this->_frameRate = rhs._frameRate; if(rhs._animation != nullptr) { delete this->_animation; this->_animation = new a2de::AnimationHandler(*rhs._animation); } else { delete this->_animation; this->_animation = nullptr; } return *this; }

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  • Project Naming Convention Feedback Please

    - by Sam Striano
    I am creating a ASP.NET MVC 3 application using Entity Framework 4. I am using the Repository/Service Pattern and was looking for feedback. I currently have the following: MVC Application (GTG.dll) GTG GTG.Controllers GTG.ViewModels Business POCO's (GTG.Business.dll) This contains all business objects (Customer, Order, Invoice, etc...) EF Model/Repositories (GTG.Data.dll) GTG.Business (GTG.Context.tt) I used the Entity POCO Generator Templates. GTG.Data.Repositories Service Layer (GTG.Data.Services.dll) GTG.Data.Services - Contains all of the service objects, one per aggregate root. The following is a little sample code: Controller Namespace Controllers Public Class HomeController Inherits System.Web.Mvc.Controller Function Index() As ActionResult Return View(New Models.HomeViewModel) End Function End Class End Namespace Model Namespace Models Public Class HomeViewModel Private _Service As CustomerService Public Property Customers As List(Of Customer) Public Sub New() _Service = New CustomerService _Customers = _Service.GetCustomersByBusinessName("Striano") End Sub End Class End Namespace Service Public Class CustomerService Private _Repository As ICustomerRepository Public Sub New() _Repository = New CustomerRepository End Sub Function GetCustomerByID(ByVal ID As Integer) As Customer Return _Repository.GetByID(ID) End Function Function GetCustomersByBusinessName(ByVal Name As String) As List(Of Customer) Return _Repository.Query(Function(x) x.CompanyName.StartsWith(Name)).ToList End Function End Class Repository Namespace Data.Repositories Public Class CustomerRepository Implements ICustomerRepository Public Sub Add(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Add End Sub Public Sub Delete(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Business.Customer Implements IRepository(Of Business.Customer).GetByID Using db As New GTGContainer Return db.Customers.FirstOrDefault(Function(x) x.ID = ID) End Using End Function Public Function Query(ByVal Predicate As System.Linq.Expressions.Expression(Of System.Func(Of Business.Customer, Boolean))) As System.Linq.IQueryable(Of Business.Customer) Implements IRepository(Of Business.Customer).Query Using db As New GTGContainer Return db.Customers.Where(Predicate) End Using End Function Public Sub Save(ByVal Entity As Business.Customer) Implements IRepository(Of Business.Customer).Save End Sub End Class End Namespace

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  • Checking if user owns file before deleting it

    - by Martin Hoe
    I'm building an API for my site that allows users to delete the files they upload. Obviously, I want to check if the user owns that file before they delete it through the API. I have a files table and a users table, here's the schema: f_id, s_id, u_id, name, size, uploaded u_id, username, password, email, activated, activation_code u_id is a foreign key. The u_id field in the files table points to the u_id in the users table. Given the users username, I want to find the users u_id, and then check if they own the file through the file ID (f_id). I wrote this SQL: $sql = 'SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f_id = ? AND u.u_id = ? LIMIT 1'; I'm assuming that'd work if I was given the users u_id in the API request, but alas I'm given only their username. How can I modify that SQL to find their user ID and use that? Thanks. Edit: Alright I've got this query but it's always returning an empty result set even though both the file ID and username exist. SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f.f_id = ? AND u.username = ? LIMIT 1

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  • eclipse stuck at running program

    - by user1434388
    This is the picture after I end task the eclipse. My Android Program has no errors, and before this problem it was all fine. It happened when I added some code into my program. It gets stuck after I click the run button. This also happens when I run my handphone for debugging the program. Other programs are all working fine, only one is stuck. When I try to remove and import it again seem there is a classes.dex file which I cannot delete, I have to restart my computer for it to allow to delete and I have to force the program to close. I have searched at this website and they said keep open the emulator but it doesn't work for me. below is the connecting coding that i added. //check internet connection private boolean chkConnectionStatus(){ ConnectivityManager connMgr = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE); final android.net.NetworkInfo wifi = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI); final android.net.NetworkInfo mobile = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE); if( wifi.isAvailable() ){ return true; } else if( mobile.isAvailable() ){ return true; } else { Toast.makeText(this, "Check your internet" , Toast.LENGTH_LONG).show(); return false; } }

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  • Best approach to cache Counts from SQL tables ?

    - by pixel3cs
    I would like to develop a Forum from scratch, with special needs and customization. I would like to prepare my forum for intensive usage and wondering how to cache things like User posts count and User replies count. Having only three tables, tblForum, tblForumTopics, tblForumReplies, what is the best approach of cache the User topics and replies counts ? Think at a simple scenario: user press a link and open the Replies.aspx?id=x&page=y page, and start reading replies. On the HTTP Request, the server will run an SQL command wich will fetch all replies for that page, also "inner joining with tblForumReplies to find out the number of User replies for each user that replied." select tblForumReplies.*, tblFR.TotalReplies from tblForumReplies inner join ( select IdRepliedBy, count(*) as TotalReplies from tblForumReplies group by IdRepliedBy ) as tblFR on tblFR.IdRepliedBy = tblForumReplies.IdRepliedBy Unfortunately this approach is very cpu intensive, and I would like to see your ideas of how to cache things like table Counts. If counting replies for each user on insert/delete, and store it in a separate field, how to syncronize with manual data changing. Suppose I will manually delete Replies from SQL.

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  • Freeing ImageData when deleting a Canvas

    - by user578770
    I'm writing a XUL application using HTML Canvas to display Bitmap images. I'm generating ImageDatas and imporingt them in a canvas using the putImageData function : for(var pageIndex=0;pageIndex<100;pageIndex++){ this.img = imageDatas[pageIndex]; /* Create the Canvas element */ var imgCanvasTmp = document.createElementNS("http://www.w3.org/1999/xhtml",'html:canvas'); imgCanvasTmp.setAttribute('width', this.img.width); imgCanvasTmp.setAttribute('height', this.img.height); /* Import the image into the Canvas */ imgCanvasTmp.getContext('2d').putImageData(this.img, 0, 0); /* Use the Canvas into another part of the program (Commented out for testing) */ // this.displayCanvas(imgCanvasTmp,pageIndex); } The images are well imported but there seems to be a memory leak due to the putImageData function. When exiting the "for" loop, I would expect the memory allocated for the Canvas to be freed but, by executing the code without executing putImageData, I noticed that my program at the end use 100Mb less (my images are quite big). I came to the conclusion that the putImageData function prevent the garbage collector to free the allocated memory. Do you have any idea how I could force the garbage collector to free the memory? Is there any way to empty the Canvas? I already tried to delete the canvas using the delete operator or to use the clearRect function but it did nothing. I also tried to reuse the same canvas to display the image at each iteration but the amount of memory used did not changed, as if the image where imported without deleting the existing ones...

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  • List all foreign key constraints that refer to a particular column in a specific table

    - by Sid
    I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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  • Copy object using pointer (templates)

    - by Azodious
    How the push_back of stl::vector is implemented so it can make copy of any datatype .. may be pointer, double pointer and so on ... I'm implementing a template class having a function push_back almost similar to vector. Within this method a copy of argument should be inserted in internal memory allocated memory. but the argument is a pointer. (an object pointer). Can you pls tell how to create copy from pointer. so that if i delete the pointer in caller still the copy exists in my template class? Code base is as follows: template<typename T> class Vector { public: void push_back(const T& val_in) { T* a = *(new T(val_in)); m_pData[SIZE++] = a; } } Caller: Vector<MyClass*> v(3); MyClass* a = new MyClass(); a->a = 0; a->b = .5; v.push_back(a); delete a; Thanks.

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  • remove row on click on specific td of that row by jquery

    - by I Like PHP
    i have an table <table class="oldService"> <thead> <th>name</th> <th>age</th> <th>action</th> </thead> <tbody> <?php foreach($array as $k=>$v){ ?> <tr> <td><?php echo $k[name] ?></td> <td><?php echo $k[age]?></td> <td id="<?php $k[id]" class="delme">X</td> </tr> <?php } ?> </tbody> <table> now i want to delete any row by clicking on X of each row except first and last row, and also need to confirm before deletion. i used below jquery <script type="text/javascript"> jQuery(document).ready(function(){ jQuery('table.oldService>tbody tr').not(':first').not(':last').click(function(){ if(confirm('want to delete!')){ jQuery(jQuery(this).addClass('del').fadeTo(400, 0, function() { jQuery(this).remove()})); jQuery.get('deleteService.php', {id:jQuery(this).attr('id')}); } else return false;}); }); </script> this is working perfect,but it execute by click on that row( means any td), i want that this event only occour when user click on X(third td) . please suggest me how to modify this jquery so that the event occur on click of X.

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  • Identifying memory leaks in C++

    - by Dororo
    I've got the following bit of code, which I've narrowed down to be causing a memory leak (that is, in Task Manager, the Private Working Set of memory increases with the same repeated input string). I understand the concepts of heaps and stacks for memory, as well as the general rules for avoiding memory leaks, but something somewhere is still going wrong: while(!quit){ char* thebuffer = new char[210]; //checked the function, it isn't creating the leak int size = FuncToObtainInputTextFromApp(thebuffer); //stored in thebuffer string bufferstring = thebuffer; int startlog = bufferstring.find("$"); int endlog = bufferstring.find("&"); string str_text=""; str_text = bufferstring.substr(startlog,endlog-startlog+1); String^ str_text_m = gcnew String(str_text_m.c_str()); //some work done delete str_text_m; delete [] thebuffer; } The only thing I can think of is it might be the creation of 'string str_text' since it never goes out of scope since it just reloops in the while? If so, how would I resolve that? Defining it outside the while loop wouldn't solve it since it'd also remain in scope then too. Any help would be greatly appreciated.

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  • JavaScript array random index insertion and deletion

    - by Tomi
    I'm inserting some items into array with randomly created indexes, for example like this: var myArray = new Array(); myArray[123] = "foo"; myArray[456] = "bar"; myArray[789] = "baz"; ... In other words array indexes do not start with zero and there will be "numeric gaps" between them. My questions are: Will these numeric gaps be somehow allocated (and therefore take some memory) even when they do not have assigned values? When I delete myArray[456] from upper example, would items below this item be relocated? EDIT: Regarding my question/concern about relocation of items after insertion/deletion - I want to know what happens with the memory and not indexes. More information from wikipedia article: Linked lists have several advantages over dynamic arrays. Insertion of an element at a specific point of a list is a constant-time operation, whereas insertion in a dynamic array at random locations will require moving half of the elements on average, and all the elements in the worst case. While one can "delete" an element from an array in constant time by somehow marking its slot as "vacant", this causes fragmentation that impedes the performance of iteration.

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  • Passing values for method

    - by Kasun
    I beginner for programming. So can you please show me how to pass values for your compile() method. class CL { private const string clexe = @"cl.exe"; private const string exe = "Test.exe", file = "test.cpp"; private string args; public CL(String[] args) { this.args = String.Join(" ", args); this.args += (args.Length > 0 ? " " : "") + "/Fe" + exe + " " + file; } public Boolean Compile(String content, ref string errors) { //remove any old copies if (File.Exists(exe)) File.Delete(exe); if (File.Exists(file)) File.Delete(file); File.WriteAllText(file, content); Process proc = new Process(); proc.StartInfo.UseShellExecute = false; proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.RedirectStandardError = true; proc.StartInfo.FileName = clexe; proc.StartInfo.Arguments = this.args; proc.StartInfo.CreateNoWindow = true; proc.Start(); //errors += proc.StandardError.ReadToEnd(); errors += proc.StandardOutput.ReadToEnd(); proc.WaitForExit(); bool success = File.Exists(exe); return success; } }

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  • help with basic MVC project

    - by Shrewd Demon
    hi, i am creating a demo MVC project and i am getting a Null Object Reference error for the following code. <% foreach (var item in Model) { %> <tr> <td> <%= Html.ActionLink("Edit", "Edit", new { /* id=item.PrimaryKey */ }) %> | <%= Html.ActionLink("Details", "Details", new { /* id=item.PrimaryKey */ })%> | <%= Html.ActionLink("Delete", "Delete", new { /* id=item.PrimaryKey */ })%> </td> <td> <%= Html.Encode(item.ContactEmail) %> </td> <td> <%= Html.Encode(item.YourQuery) %> </td> </tr> <% } %> i get an error in the first line itself (var item in Model) coz i am getting the Model object as null. Can anyone please help me. thanks.

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  • Locking a GDI+ Bitmap in Native C++?

    - by user146780
    I can find many examples on how to do this in managed c++ but none for unmanaged. I want to get all the pixel data as efficiently as possible, but some of the scan0 stuff I would need more info about so I can properly iterate through the pixel data and get each rgba value from it. right now I have this: Bitmap *b = new Bitmap(filename); if(b == NULL) { return 0; } UINT w,h; w = b->GetWidth(); h = b->GetHeight(); Rect *r = new Rect(0,0,w,h); BitmapData *lockdat; b->LockBits(r,ImageLockModeRead,PixelFormatDontCare,lockdat); delete(r); if(w == 0 && h == 0) { return 0; } Color c; std::vector<GLubyte> pdata(w * h * 4,0.0); for (unsigned int i = 0; i < h; i++) { for (unsigned int j = 0; j < w; j++) { b->GetPixel(j,i,&c); pdata[i * 4 * w + j * 4 + 0] = (GLubyte) c.GetR(); pdata[i * 4 * w + j * 4 + 1] = (GLubyte) c.GetG(); pdata[i * 4 * w + j * 4 + 2] = (GLubyte) c.GetB(); pdata[i * 4 * w + j * 4 + 3] = (GLubyte) c.GetA(); } } delete(b); return CreateTexture(pdata,w,h); How do I use lockdat to do the equivalent of getpixel? Thanks

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  • Generic Func<> as parameter to base method

    - by WestDiscGolf
    I might be losing the plot, but I hope someone can point me in the right direction. What am I trying to do? I'm trying to write some base methods which take Func< and Action so that these methods handle all of the exception handling etc. so its not repeated all over the place but allow the derived classes to specify what actions it wants to execute. So far this is the base class. public abstract class ServiceBase<T> { protected T Settings { get; set; } protected ServiceBase(T setting) { Settings = setting; } public void ExecAction(Action action) { try { action(); } catch (Exception exception) { throw new Exception(exception.Message); } } public TResult ExecFunc<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function) { try { /* what goes here?! */ } catch (Exception exception) { throw new Exception(exception.Message); } } } I want to execute an Action in the following way in the derived class (this seems to work): public void Delete(string application, string key) { ExecAction(() => Settings.Delete(application, key)); } And I want to execute a Func in a similar way in the derived class but for the life of me I can't seem to workout what to put in the base class. I want to be able to call it in the following way (if possible): public object Get(string application, string key, int? expiration) { return ExecFunc(() => Settings.Get(application, key, expiration)); } Am I thinking too crazy or is this possible? Thanks in advance for all the help.

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  • GTK+: How do I process RadioMenuItem choice without marking it chosen? And vise versa

    - by eugene.shatsky
    In my program, I've got a menu with a group of RadioMenuItem entries. Choosing one of them should trigger a function which can either succeed or fail. If it fails, this RadioMenuItem shouldn't be marked chosen (the previous one should persist). Besides, sometimes I want to set marked item without running the choice processing function. Here is my current code: # Update seat menu list def update_seat_menu(self, seats, selected_seat=None): seat_menu = self.builder.get_object('seat_menu') # Delete seat menu items for menu_item in seat_menu: # TODO: is it a good way? does remove() delete obsolete menu_item from memory? if menu_item.__class__.__name__ == 'RadioMenuItem': seat_menu.remove(menu_item) # Fill menu with new items group = [] for seat in seats: menu_item = Gtk.RadioMenuItem.new_with_label(group, str(seat[0])) group = menu_item.get_group() seat_menu.append(menu_item) if str(seat[0]) == selected_seat: menu_item.activate() menu_item.connect("activate", self.choose_seat, str(seat[0])) menu_item.show() # Process item choice def choose_seat(self, entry, seat_name): # Looks like this is called when item is deselected, too; must check if active if entry.get_active(): # This can either succeed or fail self.logind.AttachDevice(seat_name, '/sys'+self.device_syspath, True) Chosen RadioMenuItem gets marked irrespective of the choose_seat() execution result; and the only way to set marked item without triggering choose_seat() is to re-run update_seat_menu() with selected_seat argument, which is an overkill. I tried to connect choose_seat() with 'button-release-event' instead of 'activate' and call entry.activate() in choose_seat() if AttachDevice() succeeds, but this resulted in whole X desktop lockup until AttachDevice() timed out, and chosen item still got marked.

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  • got undefined variable in php code

    - by Newbie New
    I got a error message when I run my php however the result is come out this is my code function cart() { foreach($_SESSION as $name => $value) { if ($value>0) { if (substr($name, 0, 5) == 'cart_'){ $id = substr($name, 5, (strlen($name)-5)); $get = mysql_query('SELECT id, name, price FROM products WHERE id=' .mysql_real_escape_string((int)$id)); while ($get_row = mysql_fetch_assoc($get)){ $sub = $get_row['price'] * $value; echo $get_row['name'].' x '.$value.' @ &pound'.number_format($get_row['price'], 2).' = &pound'.number_format($sub, 2).' <a href="cart.php?remove='.$id.'">[-]</a> <a href="cart.php?add='.$id.'">[+]</a> <a href="cart.php?delete='.$id.'">[Delete]</a><br />' ; } } $total += $sub; } } echo $total; } ?> I got a error message Notice: Undefined variable: total in C:\xampp\htdocs\shoppingcart\cart.php on line 54 which line 54 is echo $total; what's wrong with my code?? I think I have defined the code in $total += $sub; thanks for helping me :)

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  • Combine Arbitrary number of polygons together

    - by Jakobud
    I have an arbitrary number of polygons (hexes in this case) that are arranged randomly, but they are all touching another hex. Each individual hex has 6 x,y vertices. The vertex's are known for all the hexes. Can anyone point me in the direction of an algorithm that will combine all the hexes into a single polygon? Essentially I'm just looking for a function that spits out an array of vertex locations that are ordered in a way that when drawing lines from one to the next, it forms the polygon. This is my method so far: Create array of all the vertices for all the hexes. Determine the number of times a vertex occurs in the array If vertex is in the array 3+ times, delete the vertices from the array. If vertex is in the array 2 times, delete one of them. The next step is tricky though. I'm using canvas to draw out these polygons, which essentially involves drawing a line from one vertex to the next. So the order of the vertices in the final array is important. It can't be sorted arbitrarily. Also, I'm not looking for a "convex hull" algorithm, as that would not draw the polygon correctly. Are there any functions out there that do something like this? Am I on the right track or is there a better more efficient way?

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  • What does the destructor do silently?

    - by zhanwu
    Considering the following code which looks like that the destructor doesn't do any real job, valgrind showed me clearly that it has memory leak without using the destructor. Any body can explain me what does the destructor do in this case? #include <iostream> using namespace std; class A { private: int value; A* follower; public: A(int); ~A(); void insert(int); }; A::A(int n) { value = n; follower = NULL; } A::~A() { if (follower != NULL) delete follower; cout << "do nothing!" << endl; } void A::insert(int n) { if (this->follower == NULL) { A* f = new A(n); this->follower = f; } else this->follower->insert(n); } int main(int argc, char* argv[]) { A* objectA = new A(1); int i; for (i = 0; i < 10; i++) objectA->insert(i); delete objectA; }

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  • Boost shared_ptr use_count function

    - by photo_tom
    My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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  • Can you explain this generics behavior and if I have a workaround?

    - by insta
    Sample program below: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace GenericsTest { class Program { static void Main(string[] args) { IRetrievable<int, User> repo = new FakeRepository(); Console.WriteLine(repo.Retrieve(35)); } } class User { public int Id { get; set; } public string Name { get; set; } } class FakeRepository : BaseRepository<User>, ICreatable<User>, IDeletable<User>, IRetrievable<int, User> { // why do I have to implement this here, instead of letting the // TKey generics implementation in the baseclass handle it? //public User Retrieve(int input) //{ // throw new NotImplementedException(); //} } class BaseRepository<TPoco> where TPoco : class,new() { public virtual TPoco Create() { return new TPoco(); } public virtual bool Delete(TPoco item) { return true; } public virtual TPoco Retrieve<TKey>(TKey input) { return null; } } interface ICreatable<TPoco> { TPoco Create(); } interface IDeletable<TPoco> { bool Delete(TPoco item); } interface IRetrievable<TKey, TPoco> { TPoco Retrieve(TKey input); } } This sample program represents the interfaces my actual program uses, and demonstrates the problem I'm having (commented out in FakeRepository). I would like for this method call to be generically handled by the base class (which in my real example is able to handle 95% of the cases given to it), allowing for overrides in the child classes by specifying the type of TKey explicitly. It doesn't seem to matter what parameter constraints I use for the IRetrievable, I can never get the method call to fall through to the base class. Also, if anyone can see an alternate way to implement this kind of behavior and get the result I'm ultimately looking for, I would be very interested to see it. Thoughts?

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  • What's the point of indicating AllowMultiple=false on an abstract Attribute class?

    - by tvanfosson
    On a recent question about MVC attributes, someone asked whether using HttpPost and HttpDelete attributes on an action method would result in either request type being allowed or no requests being allowed (since it can't be both a Post and a Delete at the same time). I noticed that ActionMethodSelectorAttribute, from which HttpPostAttribute and HttpDeleteAttribute both derive is decorated with [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)] I had expected it to not allow both HttpPost and HttpDelete on the same method because of this, but the compiler doesn't complain. My limited testing tells me that the attribute usage on the base class is simply ignored. AllowMultiple seemingly only disallows two of the same attribute from being applied to a method/class and doesn't seem to consider whether those attributes derive from the same class which is configured to not allow multiples. Moreover, the attribute usage on the base class doesn't even preclude your from changing the attribute usage on a derived class. That being the case, what's the point of even setting the values on the base attribute class? Is it just advisory or am I missing something fundamental in how they work? FYI - it turns out that using both basically precludes that method from ever being considered. The attributes are evaluated independently and one of them will always indicate that the method is not valid for the request since it can't simultaneously be both a Post and a Delete.

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