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• final fields and thread-safety

  - by pcjuzer

  Should it be all fields, including super-fields, of a purposively immutable java class 'final' in order to be thread-safe or is it enough to have no modifier methods? Suppose I have a POJO with non-final fields where all fields are type of some immutable class. This POJO has getters-setters, and a constructor wich sets some initial value. If I extend this POJO with knocking out modifier methods, thus making it immutable, will extension class be thread-safe?

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• setter injection guice + wicket

  - by chris-gr

  Hi, I have a Wicket Web Page where I create a new Object of class A: A a = new A(User u); In A I would like to have setter injection, however this is actually not done. I have heard that one must provide an empty constructor but how is it possible to have also a non - empty constructor with setter injection?

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• javascript validation: comparing 2 text box values

  - by coure06

  I have a table with 5 rows and 2 columns. Each cell contains a text box. I want to show error if one of the text boxes in each column is empty. I want both text boxes in a row shld be filled or both shld empty. How can i do this via Asp.net validation controls?

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• Mock implementations in C++

  - by forneo

  Hi guys, I need a mock implementation of a class - for testing purposes - and I'm wondering how I should best go about doing that. I can think of two general ways: Create an interface that contains all public functions of the class as pure virtual functions, then create a mock class by deriving from it. Mark all functions (well, at least all that are to be mocked) as virtual. I'm used to doing it the first way in Java, and it's quite common too (probably since they have a dedicated interface type). But I've hardly ever seen such interface-heavy designs in C++, thus I'm wondering. The second way will probably work, but I can't help but think of it as kind of ugly. Is anybody doing that? If I follow the first way, I need some naming assistance. I have an audio system that is responsible for loading sound files and playing the loaded tracks. I'm using OpenAL for that, thus I've called the interface "Audio" and the implementation "OpenALAudio". However, this implies that all OpenAL-specific code has to go into that class, which feels kind of limiting. An alternative would be to leave the class' name "Audio" and find a different one for the interface, e.g. "AudioInterface" or "IAudio". Which would you suggest, and why?

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• jQuery Reference First Column in HTML Table

  - by Vic

  I have a table where all of the cells are INPUT tags. I have a function which looks for the first input cell and replaces it with it's value. So this: <tr id="row_0" class="datarow"> <td><input class="tabcell" value="Injuries"></td> <td><input class="tabcell" value="01"></td> becomes this: <tr id="row_0" class="datarow"> <td>Injuries</td> <td><input class="tabcell" value="01"></td> Here is the first part of the function: function setRowLabels() { var row = []; $('.dataRow').each(function(i) { row.push($('td input:eq(0)', this).val() + ' - '); $('td input:eq(0)', this).replaceWith($('td input:eq(0)', this).val()); $('td input:gt(0)', this).each(function(e) { etcetera But when the page reloads, the first column is not an input type, so it changes the second column to text too! Can I tell it to only change the first column, no matter what the type is? I tried $('td:eq(0)', this).replaceWith($('td:eq(0)', this).val()); but it does not work. Any suggestions appreciated! Thanks

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• The pImpl idiom and Testability

  - by Rimo

  The pImpl idiom in c++ aims to hide the implementation details (=private members) of a class from the users of that class. However it also hides some of the dependencies of that class which is usually regarded bad from a testing point of view. For example if class A hides its implementation details in Class AImpl which is only accessible from A.cpp and AImpl depends on a lot of other classes, it becomes very difficult to unit test class A since the testing framework has no access to the methods of AImpl and also no way to inject dependency into AImpl. This has been a problem for me lately and I am beginning to think that the pImpl idiom and writing testable code don't mix well. Has anyone come across this problem before? and have you found a solution?

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• Singletons and constants

  - by devoured elysium

  I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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• Should I denormalize a has_many has_many?

  - by Cameron

  I have this: class User < ActiveRecord::Base has_many :serials has_many :sites, :through => :series end class Serial < ActiveRecord::Base belongs_to :user belongs_to :site has_many :episodes end class Site < ActiveRecord::Base has_many :serials has_many :users, :through => :serials end class Episode < ActiveRecord::Base belongs_to :serial end I would like to do some operations on User.serials.episodes but I know this would mean all sorts of clever tricks. I could in theory just put all the episode data into serial (denormalize) and then group_by Site when needed. If I have a lot of episodes that I need to query on would this be a bad idea? thanks

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• Disregard a particular TD element

  - by RussellDias

  Below I have the code that allows me to edit a table row inline. However it edits ALL of the TDs within that row. My problem, along with the code, are stated below. Any help is appreciated. <tbody> <tr> <th scope="row">Test</th> <td class="amount">$124</td> <td class="amount" id="" >$154</td> <td class="diff">- 754</td> </tr> </tbody> The above table is just a sample. What I have been trying to accomplish is, to simply edit the TDs within that particular row, but I need it to disregard the diff TD. I'm fairly new to jQuery and have got the following code via the help of a jQuery book. $(document).ready(function() { TABLE.formwork('#current-expenses'); }); var TABLE = {}; TABLE.formwork = function(table){ var $tables = $(table); $tables.each(function () { var _table = $(this); _table.find('thead tr').append($('<th class="edit">&nbsp;</th>')); _table.find('tbody tr').append($('<td class="edit"><input type="button" value="Edit"/></td>')) }); $tables.find('.edit :button').live('click', function(e) { TABLE.editable(this); e.preventDefault(); }); } TABLE.editable = function(button) { var $button = $(button); var $row = $button.parents('tbody tr'); var $cells = $row.children('td').not('.edit'); if($row.data('flag')) { // in edit mode, move back to table // cell methods $cells.each(function () { var _cell = $(this); _cell.html(_cell.find('input').val()); }) $row.data('flag',false); $button.val('Edit'); } else { // in table mode, move to edit mode // cell methods $cells.each(function() { var _cell = $(this); _cell.data('text', _cell.html()).html(''); if($('td.diff')){ var $input = $('<input type="text" />') .val(_cell.data('text')) .width(_cell.width() - 16); _cell.append($input); } }) $row.data('flag', true); $button.val('Save'); } } I have attempted to alter the code so that it would disregard the diff class TD, but have had no luck so far.

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• Is there a way to get the current UIEvent being handled?

  - by not-

  I'm working in a class that is a delegate of another class; this other class is in a third-party library that I'd like to avoid changing if at all possible. The original class is handling a -touchesEnded event, and is delegating responsibility to me, but it doesn't pass the UIEvent itself to me. Is there a way to get a handle to the current event in progress? It's a double-tap handler, and all that is passed to me is the view being touched, and the point at which the touch occurred. I want to know exactly how many touches are involved in the event. Thanks! randy

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• PyQt4 plugin in c++ application

  - by veverica17

  How is it posible to load python script as plugin in qt based application? The basic idea would be to make a class in c++ class b { virtual void method1(); virtual void method2(); } and 'somehow' inherit it in python like class c(b): def method1: #do something def method2: #do something I need to be able to modify the gui from python( add buttons to some widgets made in c++ with qt ). Basicaly something similiar to (gedit, blender, etc) plugin architecture with qt

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• Strange C++ thread function invocation

  - by Tony

  I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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• how toaccess the attributes in another form? c#

  - by Chelsea_cole

  I have a problem in a same namespace: public partial class frmForm1 : Form // Form1 { public class Account { public string Username; public string Password; } public class ListAcc { public static int count = 0; private static List<Account> UserList; public static List<Account> Data() { return UserList; } } } public partial class frmForm2 : Form // Form2 { private void button2_Click(object sender, EventArgs e) { frmForm1.Account A; string m = frmForm1.ListAcc<A>.[0].Username; //ERROR } } How could i access the attributes (Username, Password...) in frmForm1? Someone help me? Thanks!

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• what is the reason i am getting out put is 111?

  - by kam

  Hi, #include "stdafx.h" #include<iostream.h> template<class T> class Sample { public: Sample(); static int i; }; template<class T> int Sample<T>::i = 0; template<class T> Sample<T>::Sample() { i++; cout<<i; } void main() { Sample<int>s1; Sample<float>s2; Sample<char>s3; } output: 111 what is the reason i am getting out put is 111?

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• What to prefer in the following case?

  - by GK

  say suppose I have class as : public class Age { private int age; public int getAge() { return this.age; } } In my Main class I am calling the getAge() method many times. So I wanted to know is it advisable to call so many times or call once and assign it to some variable and use that variable. Which is best and why?

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• Unable to .append(); without eliminating all the spaces in the code

  - by Adam

  $('#form_holder').append('<div id="spec_id_'+count+'"><div class="avail_container"> <input class="avail_fields" type="checkbox" checked="checked" name="special'+count+'" /><span class="avail_field_label">Special Date</span></div> <div class="avail_container"><div class="avail_time_container"><span class="field_label">Time</span> <select name="special'+count+'_time_from_1"> <?php for ($t = 0; $t<24; $t++){ ?> <option value="<?php echo $t; ?>"><?php echo $t; ?></option> <?php } ?> </select>: <select name="special'+count+'_time_from_2"> <?php for ($t = 0; $t<60; $t+=15){ ?> <option value="<?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?>"><?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?></option> <?php } ?> </select> <span class="field_label">to</span> <select name="special'+count+'_time_to_1"> <?php for ($t = 0; $t<24; $t++){ ?> <option value="<?php echo $t; ?>"><?php echo $t; ?></option> <?php } ?> </select>: <select name="special'+count+'_time_to_2"> <?php for ($t = 0; $t<60; $t+=15){ ?> <option value="<?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?>"><?php if($t == 0){ echo $t . '' . $t; }else{ echo $t; } ?></option> <?php } ?> </select> </div> </div> </div>'); I'm assuming javascript or jquery does not like breaks like I have here, because all my javascript code does not work. What would be an alternative to eliminating all the spaces, which would make viewing the code difficult?

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• Asp.net static object behaviour

  - by Circadian

  I have the following class as part of an asp.net application. public sealed class SomeClass { private static string appId = Guid.NewGuid().ToString(); public static ReadSomethingFromDb(){} public static WriteSomethingToDb(){} } There are more than one application instances in the same application pool, and they all access the same database. I want the operations performed by the above class to be uniquely tied to the instance that performed it, hence the use of the appId. So adding a record to the database would for example contain a name, address and appId. This has been simplified for discussion purposes. Assuming that I have two instances running at mysite.a and mysite.b the above class would generate two different guids. My problem is that mysite.a sometimes produces more than one guid, which is unexpected. Thank you in advance

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• When will [MFMailComposeViewController canSendMail] return NO

  - by pythonquick

  M iPhone app is using the MFMailComposeViewController class to send an in-app email with an attachment. The app will only attempt to display the mail composer dialog if the "canSendMail" method of class MFMailComposeViewController returns true (YES). Specifically, if the following method returns YES, it shows the mail composer, otherwise the user is presented with an error alert dialog stating that there are no email accounts set up on the device: - (BOOL)canDeviceSendEmail { Class mailClass = (NSClassFromString(@"MFMailComposeViewController")); return mailClass != nil && [mailClass canSendMail]; } A team of testers have reported that they get this error alert dialog, even when email accounts are set up on the device. The tester used an iPhone 3G with OS 3.1.3. Therefore the MFMailComposeViewController class must have existed, and the "canSendMail" method must have returned NO. My question is therefore: apart from the case when there are no email accounts set up on the device, in what other circumstances can the "canSendMail" method return NO? ~ Thanks

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• Minimal framework in Scala for collections with inheriting return type

  - by Rex Kerr

  Suppose one wants to build a novel generic class, Novel[A]. This class will contain lots of useful methods--perhaps it is a type of collection--and therefore you want to subclass it. But you want the methods to return the type of the subclass, not the original type. In Scala 2.8, what is the minimal amount of work one has to do so that methods of that class will return the relevant subclass, not the original? For example, class Novel[A] /* What goes here? */ { /* Must you have stuff here? */ def reverse/* What goes here instead of :Novel[A]? */ = //... def revrev/*?*/ = reverse.reverse } class ShortStory[A] extends Novel[A] /* What goes here? */ { override def reverse: /*?*/ = //... } val ss = new ShortStory[String] val ss2 = ss.revrev // Type had better be ShortStory[String], not Novel[String] Does this minimal amount change if you want Novel to be covariant? (The 2.8 collections do this among other things, but they also play with return types in more fancy (and useful) ways--the question is how little framework one can get away with if one only wants this subtypes-always-return-subtypes feature.)

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• Pin Control in HCS12

  - by Brian Lindsey

  A HCS12 microcontroller I had to buy for a class I had recently taken has 40 pins on the back side of it. The class was merely about computer organization, and so unfortunately, we never had a chance to cover all the capabilities of the chip itself. Now that the class is over, I have been thinking about using the to familiarize myself with the assembly language. I haven't found any sources that cover pin control and was wondering if anyone could possibly provide me with a hands-on pin tutorial.

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• How can I avoid huge communication classes in WCF?

  - by mafutrct

  My understanding is that all contract-implementing code has to be in a single class, that can become very large, obviously. How do I avoid this? I really prefer to have a few small classes doing one part of the communication with clients than a single behemoth class. The only idea I could think of is using multiple interfaces implemented by a single class split up by partial, but I don't this this is really solving the issue.

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• Calling a constructor to reinitialize variables doesn't seem to work?

  - by Matt

  I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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• Dynamic class_name for has_many relations

  - by vooD

  I'm trying to make has_many relation with dynamic class_name attribute class Category < ActiveRecord::Base has_many :ads, :class_name => ( lambda { return self.item_type } ) end or class Category < ActiveRecord::Base has_many :ads, :class_name => self.item_type end But i got errors: can't convert Proc into String or undefined method `item_type' for #<Class:0xb62c6c88> Thank you for any help!

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• pagination panel should remain static

  - by fusion

  i've a search form in which a user enters the keyword and the results are displayed with pagination. everything works fine except for the fact that when the user clicks on the 'Next' button, the pagination panel disappears as well when the page loads to retrieve the data through ajax. how do i make the pagination panel static, while the data is being retrieved? search.html: <form name="myform" class="wrapper"> <input type="text" name="q" id="q" onkeyup="showPage();" class="txt_search"/> <input type="button" name="button" onclick="showPage();" class="button"/> <p> </p> <div id="txtHint"></div> </form> ajax: var url="search.php"; url += "?q="+str+"&page="+page+"&list="; url += "&sid="+Math.random(); xmlHttp.onreadystatechange=stateChanged; xmlHttp.open("GET",url,true); xmlHttp.send(null); function stateChanged(){ if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ document.getElementById("txtHint").innerHTML=xmlHttp.responseText; } //end if } //end function search.php: $self = $_SERVER['PHP_SELF']; $limit = 3; //Number of results per page $adjacents = 2; $numpages=ceil($totalrows/$limit); $query = $query." ORDER BY idQuotes LIMIT " . ($page-1)*$limit . ",$limit"; $result = mysql_query($query, $conn) or die('Error:' .mysql_error()); ?> <div class="search_caption">Search Results</div> <div class="search_div"> <table class="result"> <?php while ($row= mysql_fetch_array($result, MYSQL_ASSOC)) { $cQuote = highlightWords(htmlspecialchars($row['cQuotes']), $search_result); ?> <tr> . . .display results. . . </tr> <?php } ?> </table> </div> <hr> <div class="searchmain"> <?php //Create and print the Navigation bar $nav=""; $next = $page+1; $prev = $page-1; if($page > 1) { $nav .= "<a onclick=\"showPage('','$prev'); return false;\" href=\"$self?page=" . $prev . "&q=" .urlencode($search_result) . "\">< Prev</a>"; $first = "<a onclick=\"showPage('','1'); return false;\" href=\"$self?page=1&q=" .urlencode($search_result) . "\"> << </a>" ; } else { $nav .= "&nbsp;"; $first = "&nbsp;"; } for($i = 1 ; $i <= $numpages ; $i++) { if($i == $page) { $nav .= "<span class=\"no_link\">$i</span>"; }else{ $nav .= "<a onclick=\"showPage('',$i); return false;\" href=\"$self?page=" . $i . "&q=" .urlencode($search_result) . "\">$i</a>"; } } if($page < $numpages) { $nav .= "<a onclick=\"showPage('','$next'); return false;\" href=\"$self?page=" . $next . "&q=" .urlencode($search_result) . "\">Next ></a>"; $last = "<a onclick=\"showPage('','$numpages'); return false;\" href=\"$self?page=$numpages&q=" .urlencode($search_result) . "\"> >> </a>"; } else { $nav .= "&nbsp;"; $last = "&nbsp;"; } echo $first . $nav . $last; ?> </div>

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• Misunderstanding function pointer - passing it as an argument

  - by Stef

  I want to pass a member function of class A to class B via a function pointer as argument. Please advise whether this road is leading somewhere and help me fill the pothole. #include <iostream> using namespace std; class A{ public: int dosomeA(int x){ cout<< "doing some A to "<<x <<endl; return(0); } }; class B{ public: B(int (*ptr)(int)){ptr(0);}; }; int main() { A a; int (*APtr)(int)=&A::dosomeA; B b(APtr); return 0; } This brilliant piece of code leaves me with the compiler error: cannot convert int (A::*)(int)' toint (*)(int)' in initialization Firstly I want it to compile. Secondly I don't want dosomeA to be STATIC.

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