Search Results

Search found 50723 results on 2029 pages for 'class loading'.

Page 244/2029 | < Previous Page | 240 241 242 243 244 245 246 247 248 249 250 251  | Next Page >

  • How to enforce users to create objects of class derived from mine with "new" only?

    - by sharptooth
    To implement reference counting we use an IUnknown-like interface and a smart pointer template class. The interface has implementation for all the reference-count methods, including Release(): void IUnknownLike::Release() { if( --refCount == 0 ) { delete this; } } The smart pointer template class has a copy constructor and an assignment operator both accepting raw pointers. So users can do the following: class Class : public IUnknownLike { }; void someFunction( CSmartPointer<Class> object ); //whatever function Class object; someFunction( &object ); and the program runs into undefined behavior - the object is created with reference count zero, the smart pointer is constructed and bumps it to one, then the function returns, smart pointer is destroyed, calls Release() which leads to delete of a stack-allocated variable. Users can as well do the following: struct COuter { //whatever else; Class inner;// IUnknownLike descendant }; COuter object; somefunction( &object.Inner ); and again an object not created with new is deleted. Undefined behavior at its best. Is there any way to change the IUnknownLike interface so that the user is forced to use new for creating all objects derived from IUnknownLike - both directly derived and indirectly derived (with classes in between the most derived and the base)?

    Read the article

  • Ninject: How do I inject into a class library ?

    - by DennyDotNet
    To start I'm using Ninject 1.5. I have two projects: Web project and a Class library. My DI configuration is within the Web project. Within my class library I have the following defined: public interface ICacheService<T> { string Identifier { get; } T Get(); void Set( T objectToCache, TimeSpan timeSpan ); bool Exists(); } And then a concrete class called CategoryCacheService. In my web project I bind the two: Bind( typeof( ICacheService<List<Category>> ) ).To( typeof(CategoryCacheService)).Using<SingletonBehavior>(); In my class library I have extension methods for the HtmlHelper class, for example: public static class Category { [Inject] public static ICacheService Categories { get; set; } public static string RenderCategories(this HtmlHelper htmlHelper) { var c = Categories.Get(); return string.Join(", ", c.Select(s = s.Name).ToArray()); } } I've been told that you cannot inject into static properties, instead I should use Kernel.Get<() - However... Since the code above is in a class library I don't have access to the Kernel. How can I get the Kernel from this point or is there a better way of doing this? Thanks!

    Read the article

  • Home based business would like customers to schedule via website the time, day and date they want to take a class.

    - by Alessandro Machi
    I'm using google blogger. I want to ad thumbnail images of different classes I will be offering in my home film/video/sound/lighting studio. The idea is the prospective student visits my website, sees a class they want to take, clicks the thumbnail so first read a descriptive article about the class, at which point they can schedule the class for the time, day, and date of their choosing between the hours of 5am to 9pm, 365 days a year. As soon as the student has inputed the time, day and date of the class they want, they would go to a check out page to purchase the class time. The student would then be sent an email confirmation along with the exact location, the class name, and the time and date they selected. I was thinking of using Dwolla for the check out page because Dwolla offers either no fee or 25 cents per payment transaction, but I'm not sure I can hook up to them easily enough. My blog site is not finished by a longshot. I still have to actually input all of the class thumbnail images along with descriptions, but if you need to see what the page looks like the web address is http://www.myalexlogic.com Google blogger allows for third party code to be added within movable gadgets.

    Read the article

  • How to find unmapped properties in a NHibernate mapped class?

    - by haarrrgh
    I just had a NHibernate related problem where I forgot to map one property of a class. A very simplified example: public class MyClass { public virtual int ID { get; set; } public virtual string SomeText { get; set; } public virtual int SomeNumber { get; set; } } ...and the mapping file: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MyAssembly" namespace="MyAssembly.MyNamespace"> <class name="MyClass" table="SomeTable"> <property name="ID" /> <property name="SomeText" /> </class> </hibernate-mapping> In this simple example, you can see the problem at once: there is a property named "SomeNumber" in the class, but not in the mapping file. So NHibernate will not map it and it will always be zero. The real class had a lot more properties, so the problem was not as easy to see and it took me quite some time to figure out why SomeNumber always returned zero even though I was 100% sure that the value in the database was != zero. So, here is my question: Is there some simple way to find this out via NHibernate? Like a compiler warning when a class is mapped, but some of its properties are not. Or some query that I can run that shows me unmapped properties in mapped classes...you get the idea. (Plus, it would be nice if I could exclude some legacy columns that I really don't want mapped.)

    Read the article

  • Is it possible to cancel function override in parent class and use function from top level parent

    - by Anatoliy Gusarov
    class TopParent { protected function foo() { $this->bar(); } private function bar() { echo 'Bar'; } } class MidParent extends TopParent { protected function foo() { $this->midMethod(); parent::foo(); } public function midMethod() { echo 'Mid'; } public function generalMethod() { echo 'General'; } } Now the question is if I have a class, that extends MidParent because I need to call class Target extends MidParent { //How to override this method to return TopParent::foo(); ? protected function foo() { } } So I need to do this: $mid = new MidParent(); $mid->foo(); // MidBar $taget = new Target(); $target->generalMethod(); // General $target->foo(); // Bar UPDATE Top parent is ActiveRecord class, mid is my model object. I want to use model in yii ConsoleApplication. I use 'user' module in this model, and console app doesn't support this module. So I need to override method afterFind, where user module is called. So the Target class is the class that overrides some methods from model which uses some modules that console application doesn't support.

    Read the article

  • Using abstract base to implement private parts of a template class?

    - by StackedCrooked
    When using templates to implement mix-ins (as an alternative to multiple inheritance) there is the problem that all code must be in the header file. I'm thinking of using an abstract base class to get around that problem. Here's a code sample: class Widget { public: virtual ~Widget() {} }; // Abstract base class allows to put code in .cpp file. class AbstractDrawable { public: virtual ~AbstractDrawable() = 0; virtual void draw(); virtual int getMinimumSize() const; }; // Drawable mix-in template<class T> class Drawable : public T, public AbstractDrawable { public: virtual ~Drawable() {} virtual void draw() { AbstractDrawable::draw(); } virtual int getMinimumSize() const { return AbstractDrawable::getMinimumSize(); } }; class Image : public Drawable< Widget > { }; int main() { Image i; i.draw(); return 0; } Has anyone walked that road before? Are there any pitfalls that I should be aware of?

    Read the article

  • how do i call methods from another class in android?

    - by Phani Gargey
    I have two classes in question. Both extend Activity. Class A public void displayinfo() { setContentView(R.layout.dynamicinfo); //Add some buttons dynamically here //do some processing // move on to Class B } In Class B: I want to go back to Class A state in UI if BACK button is pressed. Class B //Register a listener for this button Backbutton.setOnClickListener(new OnClickListener() { public void onClick(View arg0) { Log.i("setOnClickListener", "Pressed Back Button "); Toast.makeText(mycontext, "Pressed Back Button", Toast.LENGTH_SHORT).show(); //HERE I want to go back class's function in UI as well as restoring the sttae for that screen. } how do I do that? I looked around some questions. they did not answer clearly what I am looking for.hence the posting. thanks.I think I was adding my own Back button on the Layout I created in the Class B's UI Screen --not using the regular "Back" button on the key board. May be that was the problem.

    Read the article

  • Cloning whole form elements after clicking button

    - by FreshPro
    I have this following form <form action="" class="form-horizontal"> <div id="wrapper"> <div class="row-fluid"> <div class="span6"> <div class="control-group"> <label class="control-label"><?=$core->l("default_comm_type");?></label> <div class="controls"> <select id="fld_default_comm_type" name="fld_default_comm_type[]" defaultValue="-1" class="m-wrap span10" field="fld_default_comm_type" appEditor="true"> <?=combo_creator::render_default_comm_types()?> </select> </div> </div> </div> <div class="span4 checkerAlign"> <div class="control-group"> <div class="controls"> <?=$core->l("is_active");?> </div> </div> </div> <div class="span2 checkerAlign"><input type="checkbox" name="fld_active[]" id="fld_active" editType="booleanEdit" appEditor="true"/></div> </div> <div><a href="#" id="addMore">Add Row</a></div> </div> The question is when user clicks Add Row button, I need to create a copy of this form elements inside <div id="wrapper"> How can i do that? EDIT: SOLVED <form action="" class="form-horizontal" id="wrapper"> <div class="row-fluid"> <div class="span6"> <div class="control-group"> <label class="control-label"><?=$core->l("default_comm_type");?></label> <div class="controls"> <select id="fld_default_comm_type" name="fld_default_comm_type[]" defaultValue="-1" class="m-wrap span10" field="fld_default_comm_type" appEditor="true"> <?=combo_creator::render_default_comm_types()?> </select> </div> </div> </div> <div class="span4 checkerAlign"> <div class="control-group"> <div class="controls"> <?=$core->l("is_active");?> </div> </div> </div> <div class="span2 checkerAlign"><input type="checkbox" name="fld_active[]" id="fld_active" editType="booleanEdit" appEditor="true"/></div> </div> <a href="#" data-action="add">add</a> <a href="#" data-action="delete">delete</a> </form> In the Js part: jQuery("#addMore").click(function(){ var contents = jQuery("form").html(); jQuery("#test").append(contents); }); When add is clicked it inserts form elements just as I wanted and when delete is clicked it deletes elements. Thank you for the tips guys Problem solved! Thanks guys.

    Read the article

  • hProduct-microformats not work in google

    - by silverfox
    I'm trying to work with hProduct was testing tool for google microformats (http://www.google.com/webmasters/tools/richsnippets), but it is not recognizing the data: does not recognize the photo does not recognize the price does not recognize the category only recognizes the rating HTML: <div class="hproduct"> <span class="brand">ACME</span> <span class="fn">Executive Anvil</span> <img class="photo" src="http://microformats.org/wiki/skins/Microformats/images/logo.gif" /> <span class="review hreview-aggregate"> Average rating: <span class="rating">4.4</span>, based on <span class="count">89 </span> reviews </span> Regular price: $179.99 Sale: $<span class="price">119.99</span> (Sale ends 5 November!) <span class="description">Sleeker than ACME's Classic Anvil, the Executive Anvil is perfect for the business traveler looking for something to drop from a height.</span> Category: <span class="category"> <span class="value-title" title="Hardware > Tools > Anvils">Anvils</span> </span> </div> and still shows this warning: waring: In order to generate a preview with rich snippets, either price or review or availability needs to be present. I used google's own example: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=186036 I also tested the microformas.org: http://microformats.org/wiki/google-rich-snippets-examples

    Read the article

  • call function between classes [closed]

    - by aziz joh
    hello I have 3 classes class A, B, and C class A is the main class and content the main function also, i call class B and class C in the main as b1,b2 and c1. in class B there is a vector (V) has list of int. and 3 functions Add, get and delete delete. all the thing in the class is public. in class C i have function that need to (B::get) from b. what I want is that how I can make c1 call get of b1 to return the value of the V in b1 after that use add of b2 to add new item in V of b2. Thanks in advance This is an example class a{ int main(){ b b1,b2; c c1; b1.add(10); b1.add(20); c1.start(); }} class b{ vector<int> v; void add(int i){ v.push_back(i)} int get(){int i=v.at(0); return i;} } class c{// take something from b1 and add it to b2 void play(){ int i=b.get();//should take it from b1 b.add(i*2);//should add it to b2 }} please I need your help I been searching to solve this problem for days.

    Read the article

  • $_GET loading content before head tag instead of in specified div.

    - by s32ialx
    NOT EDITING BELOW BUT THANKS TO SOME REALLY NICE PEOPLE I CAN'T POST AN IMAGE ANYMORE BECAUSE I HAD a 15 Rep but NOW ONLY A 5 becuase my question wasn't what they wanted help with they gave me a neg rep. The problem is that the content loads it displays UNDER the div i placed #CONTENT# inside so the styles are being ignored and it's posting #CONTENT# outside the divs at positions 0,0 any suggestions? Found out whats happening by using "View Source" seems that it's putting all of the #CONTENT#, content that's being loaded in front of the <head> tag. Like this <doctype...> <div class="home"> \ blah blah #CONTENT# bot being loaded in correct specified area </div> / <head> <script src=""></script> </head> <body> <div class="header"></div> <div class="contents"> #CONTENT# < where content SHOULD load </div> <div class="footer"></div> </body> so anyone got a fix? OK so a better description I'll add relevant screen-shots Whats happening is /* file.class.php */ <?php $file = new file(); class file{ var $path = "templates/clean"; var $ext = "tpl"; function loadfile($filename){ return file_get_contents($this->path . "/" . $filename . "." . $this->ext); } function setcontent($content,$newcontent,$vartoreplace='#CONTENT#'){ $val = str_replace($vartoreplace,$newcontent,$content); return $val; } function p($content) { $v = $content; $v = str_replace('#CONTENT#','',$v); print $v; } } if(!isset($_GET['page'])){ // if not, lets load our index page(you can change home.php to whatever you want: include("main.txt"); // else $_GET['page'] was set so lets do stuff: } else { // lets first check if the file exists: if(file_exists($_GET['page'].'.txt')){ // and lets include that then: include($_GET['page'].'.txt'); // sorry mate, could not find it: } else { echo 'Sorry, could not find <strong>' . $_GET['page'] .'.txt</strong>'; } } ?> is calling for a file_get_contents at the bottom which I use in /* index.php */ <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <?php include('classes/file.class.php'); // load the templates $header = $file->loadfile('header'); $body = $file->loadfile('body'); $footer = $file->loadfile('footer'); // fill body.tpl #CONTENT# slot with $content $body = $file->setcontent($body, $content); // cleanup and output the full page $file->p($header . $body . $footer); ?> and loads into /* body.tpl */ <div id="bodys"> <div id="bodt"></div> <div id="bodm"> <div id="contents"> #CONTENT# </div> </div> <div id="bodb"></div> </div> but the issue is as follows the $content loads properly img tags etc <h2> tags etc but CSS styling is TOTALY ignored for position width z-index etc. and as follows here's the screen-shot My Firefox Showing The Problem In Action REPOSTED DUE TO PEOPLE NOT HELPING AND JUST BEING ARROGANT AND GIVING NEGATIVE VOTES and not even saying a word. DO NOT COMMENT UNLESS YOU PLAN TO HELP god I'm a beginner and with you people giving me bad reviews this won't make me help you out when the chance comes.

    Read the article

  • How do I prevent my form from freezing when it is loading an image from the web at the click of a button?

    - by Vimal Basdeo
    I want to display an image from the web to a panel in another Jframe at the click of a button but whenever I click the button first the image loads and during this time the current form potentially freezes and once the image has loaded the form is displayed with the image.. How can I avoid the situation where my form freezes since it is very irritating My codes :: My current class private void btn_TrackbusActionPerformed(java.awt.event.ActionEvent evt) { try { sendMessage("Query,map,$,start,211,Arsenal,!"); System.out.println(receiveMessage()); } catch (UnknownHostException ex) { Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex); } catch (IOException ex) { Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex); } catch (Exception ex) { Logger.getLogger(client_Trackbus.class.getName()).log(Level.SEVERE, null, ex); } client_trackedbus nextform=new client_trackedbus(planform,connection,packet_receive,packet_send); this.setVisible(false); this.dispose(); nextform.setVisible(true); // TODO add your handling code here: } My next class that displays the image public class client_trackedbus extends javax.swing.JFrame { client_planform planform=null; DatagramSocket connection=null; DatagramPacket packet_receive=null; DatagramPacket packet_send=null; JLabel label=null; /** Creates new form client_trackedbus */ public client_trackedbus(client_planform planform,DatagramSocket connection,DatagramPacket packet_receive,DatagramPacket packet_send) { initComponents(); this.planform=planform; this.connection=connection; this.packet_receive=packet_receive; this.packet_send=packet_send; try { displayMap("http://www.huddletogether.com/projects/lightbox2/images/image-2.jpg", jPanel1, new JLabel()); } catch (MalformedURLException ex) { Logger.getLogger(client_trackedbus.class.getName()).log(Level.SEVERE, null, ex); } } private void displayMap(String url,JPanel panel,JLabel label) throws MalformedURLException{ URL imageurl=new URL(url); Image image=(Toolkit.getDefaultToolkit().createImage(imageurl)); ImageIcon icon = new ImageIcon(image); label.setIcon(icon); panel.add(label); // System.out.println(panel.getSize().width); this.getContentPane().add(panel); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ @SuppressWarnings("unchecked") // <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() { jPanel1 = new javax.swing.JPanel(); jLabel1 = new javax.swing.JLabel(); btn_Exit = new javax.swing.JButton(); btn_Plan = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setTitle("Public Transport Journey Planner"); javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1); jPanel1.setLayout(jPanel1Layout); jPanel1Layout.setHorizontalGroup( jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 368, Short.MAX_VALUE) ); jPanel1Layout.setVerticalGroup( jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGap(0, 172, Short.MAX_VALUE) ); jLabel1.setFont(new java.awt.Font("Arial", 1, 18)); jLabel1.setText("Your tracked bus"); btn_Exit.setText("Exit"); btn_Exit.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { btn_ExitActionPerformed(evt); } }); btn_Plan.setText("Plan journey"); btn_Plan.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { btn_PlanActionPerformed(evt); } }); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(104, 104, 104) .addComponent(jLabel1)) .addGroup(layout.createSequentialGroup() .addContainerGap() .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)) .addGroup(layout.createSequentialGroup() .addGap(65, 65, 65) .addComponent(btn_Plan) .addGap(65, 65, 65) .addComponent(btn_Exit, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE))) .addContainerGap(20, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(35, 35, 35) .addComponent(jLabel1) .addGap(18, 18, 18) .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addGap(18, 18, 18) .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) .addComponent(btn_Exit) .addComponent(btn_Plan)) .addContainerGap(12, Short.MAX_VALUE)) ); pack(); }// </editor-fold> private void btn_ExitActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: Exitform(); } private void btn_PlanActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: this.setVisible(false); this.dispose(); this.planform.setVisible(true); } private void Exitform(){ this.setVisible(false); this.dispose(); } /** * @param args the command line arguments */ public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { // new client_trackedbus().setVisible(true); } }); } // Variables declaration - do not modify private javax.swing.JButton btn_Exit; private javax.swing.JButton btn_Plan; private javax.swing.JLabel jLabel1; private javax.swing.JPanel jPanel1; // End of variables declaration }

    Read the article

  • Any difference between lazy loading Javascript files vs. placing just before </body>

    - by mhr
    Looked around, couldn't find this specific question discussed. Pretty sure the difference is negligible, just curious as to your thoughts. Scenario: All Javascript that doesn't need to be loaded before page render has been placed just before the closing </body> tag. Are there any benefits or detriments to lazy loading these instead through some Javascript code in the head that executes when the DOM load/ready event is fired? Let's say that this only concerns downloading one entire .js file full of functions and not lazy loading several individual files as needed upon usage. Hope that's clear, thanks.

    Read the article

  • Best way to show a loading screen in an iPhone app?

    - by pkulak
    I'm building what is essentially a web app. Every piece of data has to be fetched from a web API. So, every UITableView that I show takes some amount of time to fill with data and I'm struggling to find a good way to show the user a loading screen. Right now I'm popping up an action sheet, but that just seems a bit wrong. Ideally, I'd popup up a blank view over the tableview with "Loading..." on it, then fade it away when the data comes in, but I can't think of a way to do that in 8 places in my app without massive code duplication.

    Read the article

  • Loading a datagrid with large amounts of data in silverlight?

    - by JD
    Hi I am breaking up my project in small sections and one of the sections involves loading a grid with possibily lots of records (could be up to 1000s of records in the database). Ideally I would like some sort of mechanism where as the users scrolls the grid, more data is retrieved. I have read that certain controls (datapager with RIA) do this but I would like to know how I could implement this myself or do something similiar? I was thinking about first loading 50 records at a time and when the user gets to scroll near the 50th record, then get another 50 as a start and so on. Not sure how I do this but this does not feel right or whether I should load ids of records in the grid and then get each row to load itself via an async thread but then I am hitting my database for each record? Thanks JD.

    Read the article

  • Where should I put some code for loading application data?

    - by cgp
    I have a tab-bar and navigation controller application (like Youtube app or Contacts app). Where is the correct place to have the code for loading some data from the web? These data are necessary for all the tabs of the Tab Controller and the app can't display anything before all data are downloaded and parsed from the app (except a loading indicator view of course). Up to now I put it in the AppDelegate but it somehow doesn't feel right.. What's the correct way to do it? Thanks!

    Read the article

  • Loading an XML file with todays date in the filename... need to fallback to old file if one with tod

    - by arala22
    So here is my question. Using javascript/jQuery I am currently loading in an XML file that has a file name such as carousel_large_2010-06-08.xml.. the way I am doing it is checked for todays date then grabbing a file that has that date in the filename... the issue is sometimes they wont be uploading a new file for a given day so it needs to fallback to a older date that exists.. Wondering how to do it? Here is my code: // set date for xml file var currentTime = new Date(), month = currentTime.getMonth() + 1, day = currentTime.getDate(), year = currentTime.getFullYear(); if(month.toString().length == 1){ month = '0'+month.toString(); } if(day.toString().length == 1){ day = '0'+day.toString(); } var dateObject = year+"-"+month+"-"+day; // start magic $jq.ajax({ type: "GET", url: "_xml/carousel/home/carousel_large_"+dateObject+".xml", dataType: "xml", success: HPCarousels.heroCarousel.parseXML, error: function(){ alert('Error Loading XML Content'); } });

    Read the article

  • Displaying a "Loading..." screen in a UITableView like the AppStore App...

    - by Mugunth Kumar
    the App Store app and fairly a lot many apps display a view that says "Loading.." while the content is being retrieved. How can we do this? Should I remove the UITableView and call addSubView and then once the data is available, add the tableview back? Or is there any other shortcut? If my question is not clear, please see this image... http://www.flickr.com/photos/mugunthkumar/3774575906/ I want to know how to create a temporary loading view like this till my tableview contents are ready...

    Read the article

  • Why does decorating a class break the descriptor protocol, thus preventing staticmethod objects from behaving as expected?

    - by Robru
    I need a little bit of help understanding the subtleties of the descriptor protocol in Python, as it relates specifically to the behavior of staticmethod objects. I'll start with a trivial example, and then iteratively expand it, examining it's behavior at each step: class Stub: @staticmethod def do_things(): """Call this like Stub.do_things(), with no arguments or instance.""" print "Doing things!" At this point, this behaves as expected, but what's going on here is a bit subtle: When you call Stub.do_things(), you are not invoking do_things directly. Instead, Stub.do_things refers to a staticmethod instance, which has wrapped the function we want up inside it's own descriptor protocol such that you are actually invoking staticmethod.__get__, which first returns the function that we want, and then gets called afterwards. >>> Stub <class __main__.Stub at 0x...> >>> Stub.do_things <function do_things at 0x...> >>> Stub.__dict__['do_things'] <staticmethod object at 0x...> >>> Stub.do_things() Doing things! So far so good. Next, I need to wrap the class in a decorator that will be used to customize class instantiation -- the decorator will determine whether to allow new instantiations or provide cached instances: def deco(cls): def factory(*args, **kwargs): # pretend there is some logic here determining # whether to make a new instance or not return cls(*args, **kwargs) return factory @deco class Stub: @staticmethod def do_things(): """Call this like Stub.do_things(), with no arguments or instance.""" print "Doing things!" Now, naturally this part as-is would be expected to break staticmethods, because the class is now hidden behind it's decorator, ie, Stub not a class at all, but an instance of factory that is able to produce instances of Stub when you call it. Indeed: >>> Stub <function factory at 0x...> >>> Stub.do_things Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'function' object has no attribute 'do_things' >>> Stub() <__main__.Stub instance at 0x...> >>> Stub().do_things <function do_things at 0x...> >>> Stub().do_things() Doing things! So far I understand what's happening here. My goal is to restore the ability for staticmethods to function as you would expect them to, even though the class is wrapped. As luck would have it, the Python stdlib includes something called functools, which provides some tools just for this purpose, ie, making functions behave more like other functions that they wrap. So I change my decorator to look like this: def deco(cls): @functools.wraps(cls) def factory(*args, **kwargs): # pretend there is some logic here determining # whether to make a new instance or not return cls(*args, **kwargs) return factory Now, things start to get interesting: >>> Stub <function Stub at 0x...> >>> Stub.do_things <staticmethod object at 0x...> >>> Stub.do_things() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'staticmethod' object is not callable >>> Stub() <__main__.Stub instance at 0x...> >>> Stub().do_things <function do_things at 0x...> >>> Stub().do_things() Doing things! Wait.... what? functools copies the staticmethod over to the wrapping function, but it's not callable? Why not? What did I miss here? I was playing around with this for a bit and I actually came up with my own reimplementation of staticmethod that allows it to function in this situation, but I don't really understand why it was necessary or if this is even the best solution to this problem. Here's the complete example: class staticmethod(object): """Make @staticmethods play nice with decorated classes.""" def __init__(self, func): self.func = func def __call__(self, *args, **kwargs): """Provide the expected behavior inside decorated classes.""" return self.func(*args, **kwargs) def __get__(self, obj, objtype=None): """Re-implement the standard behavior for undecorated classes.""" return self.func def deco(cls): @functools.wraps(cls) def factory(*args, **kwargs): # pretend there is some logic here determining # whether to make a new instance or not return cls(*args, **kwargs) return factory @deco class Stub: @staticmethod def do_things(): """Call this like Stub.do_things(), with no arguments or instance.""" print "Doing things!" Indeed it works exactly as expected: >>> Stub <function Stub at 0x...> >>> Stub.do_things <__main__.staticmethod object at 0x...> >>> Stub.do_things() Doing things! >>> Stub() <__main__.Stub instance at 0x...> >>> Stub().do_things <function do_things at 0x...> >>> Stub().do_things() Doing things! What approach would you take to make a staticmethod behave as expected inside a decorated class? Is this the best way? Why doesn't the builtin staticmethod implement __call__ on it's own in order for this to just work without any fuss? Thanks.

    Read the article

< Previous Page | 240 241 242 243 244 245 246 247 248 249 250 251  | Next Page >