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  • Is it OK to write a constructor which does nothing?

    - by Roman
    To use methods of a class I need to instantiate a class. At the moment the class has not constructor (so I want to write it). But than I have realized that the constructor should do nothing (I do need to specify values of fields). In this context I have a question if it is OK to write constructor which does nothing. For example: public Point() { }

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  • XCode enum woes

    - by Raconteur
    Hi gang, I thought I had this sorted, but I am still missing something. Very simply, I have a Settings class that hold a DAO (sitting on a plist). I want to have a couple of enums for the settings for convenience and readability, such as GamePlayType and DifficultyLevel. Right now I am defining them in the Settings.h file above the @interface line as such: typedef enum { EASY, NORMAL, HARD } DifficultyLevel; and typedef enum { SET_NUMBER_OF_MOVES, TO_COMPLETION } GamePlayType; If I access them from within the Settings class like: - (int)gridSizeForLOD { switch ([self difficultyLevel]) { case EASY: return GRID_SIZE_EASY; case NORMAL: return GRID_SIZE_NORMAL; case HARD: return GRID_SIZE_HARD; default: return GRID_SIZE_NORMAL; } } everything is fine. But, if I try to access them outside of the Settings class, let's say in my main view controller class, like this: if (([settings gameType] == SET_NUMBER_OF_MOVES) && (numMoves == [settings numMovesForLOD])) { [self showLoseScreen]; } I get errors (like EXC_BAD_ACCESS) or the condition always fails. Am I doing something incorrectly? Also, I should point out that I have this code for the call to gameType (which lives in the Settings class): - (GamePlayType)gameType { return [dao gameType]; } and the DAO implements gameType like this: - (int)gameType { return (settingsContent != nil) ? [[settingsContent objectForKey:@"Game Type"] intValue] : 0; } I know I have the DAO returning an int instead of a GamePlayType, but A) the problem I am describing arose there when I tried to use the "proper" data type, and B) I did not think it would matter since the enum is just a bunch of named ints, right? Any help, greatly appreciated. I really want to understand this thoroughly, and something is eluding me... Cheers, Chris

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  • jQuery validate plugin radio with optional text

    - by timborden
    I'm trying to figure out how to validate a form element with a mix of radio inputs and a text input: <label>Question?</label> <input type="radio" class="mandatory" name="questions[1][]" value="1" />answer 1<br/> <input type="radio" class="mandatory" name="questions[1][]" value="2" />answer 2<br/> <input class="ignore" type="radio" id="questions[1][]" />Other (please specify)<br/> <input class="optional mandatory" type="text" name="questions[1][]" value="" /> I've figured out how to get the form to behave as expected (select and unselect) with the following code: $("input.optional").focus(function () { var this_name = $(this).attr("name"); $("input:radio").filter(function() {return $(this).attr('name') == this_name; }).attr('checked', false); $("input").filter(function() {return $(this).attr('id') == this_name; }).attr('checked', true); }); $(':radio').click(function () { var this_name = $(this).attr("name"); $("input").filter(function() {return $(this).attr('id') == this_name; }).attr('checked', false); $("input.optional").filter(function() {return $(this).attr('name') == this_name; }).val(''); }); I was hoping I could use the class "mandatory" to validate the mix of radio and text inputs: $("form .manditory").each(function () { $(this).rules("add", {required: true}); }); But it's not working as expected. With the radio (id="questions[1][]") selected, and the text input containing content, the form element is still flagged as invalid. Suggestions...maybe a better approach? Thanks in advance. UPDATE Sorry, I should have clarified that I'm using the validate plugin: $("form").validate({ ... });

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  • Help decoding MSDN Dynamic Data Article

    - by davemackey
    I'm trying to run through this msdn article: http://msdn.microsoft.com/en-us/library/dd723645.aspx One of the steps is: In the class file for the page, change the base class from UserControl to EntityTemplateUserControl. Nowhere is it made clear what page is being referenced. Can someone help me? I don't see any relevant class in the pages I have, so I assumed maybe they were talking about the ascx and didn't really mean page, but I'm not seeing an option there either.

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  • Python: why can't descriptors be instance variables?

    - by Continuation
    Say I define this descriptor: class MyDescriptor(object): def __get__(self, instance, owner): return self._value def __set__(self, instance, value): self._value = value def __delete__(self, instance): del(self._value) And I use it in this: class MyClass1(object): value = MyDescriptor() >>> m1 = MyClass1() >>> m1.value = 1 >>> m2 = MyClass1() >>> m2.value = 2 >>> m1.value 2 So value is a class attribute and is shared by all instances. Now if I define this: class MyClass2(object) value = 1 >>> y1 = MyClass2() >>> y1.value=1 >>> y2 = MyClass2() >>> y2.value=2 >>> y1.value 1 In this case value is an instance attribute and is not shared by the instances. Why is it that when value is a descriptor it can only be a class attribute, but when value is a simple integer it becomes an instance attribute?

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  • How can I disable a model field in a django form

    - by jammon
    I have a model like this: class MyModel(models.Model): REGULAR = 1 PREMIUM = 2 STATUS_CHOICES = ((REGULAR, "regular"), (PREMIUM, "premium")) name = models.CharField(max_length=30) status = models.IntegerField(choices = STATUS_CHOICES, default = REGULAR) class MyForm(forms.ModelForm): class Meta: model = models.MyModel In a view I initialize one field and try to make it non-editable: myform = MyForm(initial = {'status': requested_status}) myform.fields['status'].editable = False But the user can still change that field. What's the real way to accomplish what I'm after?

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  • c++ templates: problem with member specialization

    - by ChAoS
    I am attempting to create a template "AutoClass" that create an arbitrary class with an arbitrary set of members, such as: AutoClass<int,int,double,double> a; a.set(1,1); a.set(0,2); a.set(3,99.7); std::cout << "Hello world! " << a.get(0) << " " << a.get(1) << " " << a.get(3) << std::endl; By now I have an AutoClass with a working "set" member: class nothing {}; template < typename T1 = nothing, typename T2 = nothing, typename T3 = nothing, typename T4 = nothing, typename T5 = nothing, typename T6 = nothing> class AutoClass; template <> class AutoClass<nothing, nothing, nothing, nothing, nothing, nothing> { public: template <typename U> void set(int n,U v){} }; template < typename T1, typename T2, typename T3, typename T4, typename T5, typename T6> class AutoClass: AutoClass<T2,T3,T4,T5,T6> { public: T1 V; template <typename U> void set(int n,U v) { if (n <= 0) V = v; else AutoClass<T2,T3,T4,T5,T6>::set(n-1,v); } }; and I started to have problems implementing the corresponding "get". This approach doesn't compile: template < typename T1, typename T2, typename T3, typename T4, typename T5, typename T6> class AutoClass: AutoClass<T2,T3,T4,T5,T6> { public: T1 V; template <typename U> void set(int n,U v) { if (n <= 0) V = v; else AutoClass<T2,T3,T4,T5,T6>::set(n-1,v); } template <typename W> W get(int n) { if (n <= 0) return V; else return AutoClass<T2,T3,T4,T5,T6>::get(n-1); } template <> T1 get(int n) { if (n <= 0) return V; else return AutoClass<T2,T3,T4,T5,T6>::get(n-1); } }; Besides, it seems I need to implement get for the <nothing, nothing, nothing, nothing, nothing, nothing> specialization. Any Idea on how to solve this?

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  • What are the different methods for injecting cross-cutting concerns?

    - by Stacy Vicknair
    What are the different methods for injecting cross-cutting concerns into a class so that I can minimize the coupling of the classes involved while keeping the code testable (TDD or otherwise)? For example, consider if I have a class that requires both logging functionality and centralized exception management. Should I use DIP and inject both required concerns via an interface into the class that requires them? Should I use a service locater that I pass to each class that will require some cross cutting functionality? Is there a different solution altogether? Am I asking the wrong question entirely?

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  • How should I organize my Java GUI?

    - by Spencer
    I'm creating a game in Java for fun and I'm trying to decide how to organize my classes for the GUI. So far, all the classes with only the swing components and layout (no logic) are in a package called "ui". I now need to add listeners (i.e. ActionListener) to components (i.e. button). The listeners need to communicate with the Game class. Currently I have: Game.java - creates the frame add panels to it import javax.swing.; import ui.; public class Game { private JFrame frame; Main main; Rules rules; Game() { rules = new Rules(); frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); main = new Main(); frame.setContentPane(main.getContentPane()); show(); } void show() { frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static void main(String[] args) { new Game(); } } Rules.java - game logic ui package - all classes create new panels to be swapped out with the main frame's content pane Main.java (Main Menu) - creates a panel with components Where do I now place the functionality for the Main class? In the game class? Separate class? Or is the whole organization wrong? Thanks

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  • Problem with foreach loop and $_GET

    - by phpExe
    I have a very simple foreach loop foreach($tv as $id => $channel) { $ID = $_GET['ID']; if($ID == $id){$class = "currentt";} echo '<a href="http://www.mysite.com/tst.php?ID='.$id.'" class="'.$class.'">'.$channel.'</a><br>'; } With url query, with every click the current class repeated. How can avoid this? Thanks alot.

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  • Creating an Expando object in Ruby

    - by tyndall
    Is there a better way to write this Expando class? The way it is written does not work. I'm using Ruby 1.8.7 starting code quoted from https://gist.github.com/300462/3fdf51800768f2c7089a53726384350c890bc7c3 class Expando def method_missing(method_id, *arguments) if match = method_id.id2name.match(/(\w*)(\s*)(=)(\s*)(\.*)/) puts match[1].to_sym # think this was supposed to be commented self.class.class_eval{ attr_accessor match[1].to_sym } instance_variable_set("#{match[1]}", match[5]) else super.method_missing(method_id, *arguments) end end end person = Expando.new person.name = "Michael" person.surname = "Erasmus" person.age = 29

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  • Catch a PHP Object Instantiation Error

    - by Rob Wilkerson
    It's really irking me that PHP considers the failure to instantiate an object a Fatal Error (which can't be caught) for the application as a whole. I have set of classes that aren't strictly necessary for my application to function--they're really a convenience. I have a factory object that attempts to instantiate the class variant that's indicated in a config file. This mechanism is being deployed for message storage and will support multiple store types: DatabaseMessageStore FileMessageStore MemcachedMessageStore etc. A MessageStoreFactory class will read the application's preference from a config file, instantiate and return an instance of the appropriate class. It might be easy enough to slap a conditional around the instantiation to ensure that class_exists(), but MemcachedMessageStore extends PHP's Memcached class. As a result, the class_exists() test will succeed--though instantiation will fail--if the memcached bindings for PHP aren't installed. Is there any other way to test whether a class can be instantiated properly? If it can't, all I need to do is tell the user which features won't be available to them, but let them continue one with the application. Thanks.

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  • Robotlegs: Warning: Injector already has a rule for type

    - by MikeW
    I have a bunch of warning messages like this appear when using Robotlegs/Signals. Everytime this command class executes, which is every 2-3 seconds ..this message displays below If you have overwritten this mapping intentionally you can use "injector.unmap()" prior to your replacement mapping in order to avoid seeing this message. Warning: Injector already has a rule for type "mx.messaging.messages::IMessage", named "". The command functions fine otherwise but I think I'm doing something wrong anyhow. public class MessageReceivedCommand extends SignalCommand { [Inject] public var message:IMessage; ...etc.. do something with message.. } the application context doesnt map IMessage to this command, as I only see an option to mapSignalClass , besides the payload is received fine. Wonder if anyone knows how I might either fix or suppress this message. I've tried calling this as the warning suggests injector.unmap(IMessage, "") but I receive an error - no mapping found for ::IMessage named "". Thanks Edit: A bit more info about the error Here is the signal that I dispatch to the command public class GameMessageSignal extends Signal { public function GameMessageSignal() { super(IMessage); } } which is dispatched from a IPushDataService class gameMessage.dispatch(message.message); and the implementation is wired up in the app context via injector.mapClass(IPushDataService, PushDataService); along with the signal signalCommandMap.mapSignalClass(GameMessageSignal, MessageReceivedCommand); Edit #2: Probably good to point out also I inject an instance of GameMessageSignal into IPushDataService public class PushDataService extends BaseDataService implements IPushDataService { [Inject] public var gameMessage:GameMessageSignal; //then private function processMessage(message:MessageEvent):void { gameMessage.dispatch(message.message); } } Edit:3 The mappings i set up in the SignalContext: injector.mapSingleton(IPushDataService); injector.mapClass(IPushDataService, PushDataService);

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  • Why One-to-one relationship dosen't work?

    - by eugenn
    I'm trying to create a very simple relationship between two objects. Can anybody explain me why I can't find the Company object via findBy method? class Company { String name String desc City city static constraints = { city(unique: true) } } class City { String name static constraints = { } } class BootStrap { def init = { servletContext -> new City(name: 'Tokyo').save() new City(name: 'New York').save() new Company(name: 'company', city: City.findByName('New York')).save() def c = Company.findByName('company') // Why c=null????! } def destroy = { } }

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  • Storing object into cache using Linq classes and velocity

    - by Arun
    I careated couple of linq classes & marked the datacontext as unidirectional. Out of four classes; one is main class while other three are having the one to many relationship with first one; When I load the object of main class & put into the memory OR serialize it into an XML file; I never get the child class data while it is maked as DataContractAttribute. How can I force object to put the child class data into XML file or into cache ?

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  • Am I doing AS3 reference cleanup correctly?

    - by Ólafur Waage
    In one frame of my fla file (let's call it frame 2), I load a few xml files, then send that data into a class that is initialized in that frame, this class creates a few timers and listeners. Then when this class is done doing it's work. I call a dispatchEvent and move to frame 3. This frame does some things as well, it's initialized and creates a few event listeners and timers. When it's done, I move to frame 2 again. This is supposed to repeat as often as I need so I need to clean up the references correctly and I'm wondering if I'm doing it correctly. For sprites I do this. world.removeChild(Background); // world is the parent stage Background = null; For instances of other classes I do this. Players[i].cleanUp(world); // do any cleanup within the instanced class world.removeChild(PlayersSelect[i]); For event listeners I do this. if(Background != null) { Background.removeEventListener(MouseEvent.CLICK, deSelectPlayer); } For timers I do this. if(Timeout != null) { Timeout.stop(); Timeout.removeEventListener(TimerEvent.TIMER, queueHandler); Timeout.removeEventListener(TimerEvent.TIMER_COMPLETE, queueCompleted); Timeout = null; } And for library images I do this if(_libImage!= null) { s.removeChild(Images._libImage); // s is the stage _libImage= null; } And for the class itself in the main timeline, I do this Frame2.removeEventListener("Done", IAmDone); Frame2.cleanUp(); // the cleanup() does all the stuff above Frame2= null; Even if I do all this, when I get to frame 2 for the 2nd time, it runs for 1-2 seconds and then I get a lot of null reference errors because the cleanup function is called prematurely. Am I doing the cleanup correctly? What can cause events to fire prematurely?

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  • Converting string to a simple type

    - by zespri
    .Net framework contains a great class named Convert that allows conversion between simple types, DateTime type and String type. Also the class support conversion of the types implementing IConvertible interface. The class has been implemented in the very first version of .Net framework. There were a few things in the first .Net framework that were not done quite right. For example .Parse methods on simple types would throw an exception if the string couldn't be parsed and there would be no way to check if exception is going to be thrown in advance. A future version of .Net Framework removed this deficiency by introducing the TryParse method that resolved this problem. The Convert class dates back to time of the old Parse method, so the ChangeType method on this class in implemented old style - if conversion can't be performed an exception is thrown. Take a look at the following code: public static T ConvertString<T>(string s, T @default) { try { return (T)Convert.ChangeType(s, typeof(T), CultureInfo.InvariantCulture); } catch (Exception) { return @default; } } This code basically does what I want. However I would pretty much like to avoid the ugly try/catch here. I'm sure, that similar to TryParse, there is a modern method of rewriting this code without the catch-all. Could you suggest one?

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  • Is there a performance gain from defining routes in app.yaml versus one large mapping in a WSGIAppli

    - by jgeewax
    Scenario 1 This involves using one "gateway" route in app.yaml and then choosing the RequestHandler in the WSGIApplication. app.yaml - url: /.* script: main.py main.py from google.appengine.ext import webapp class Page1(webapp.RequestHandler): def get(self): self.response.out.write("Page 1") class Page2(webapp.RequestHandler): def get(self): self.response.out.write("Page 2") application = webapp.WSGIApplication([ ('/page1/', Page1), ('/page2/', Page2), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() Scenario 2: This involves defining two routes in app.yaml and then two separate scripts for each (page1.py and page2.py). app.yaml - url: /page1/ script: page1.py - url: /page2/ script: page2.py page1.py from google.appengine.ext import webapp class Page1(webapp.RequestHandler): def get(self): self.response.out.write("Page 1") application = webapp.WSGIApplication([ ('/page1/', Page1), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() page2.py from google.appengine.ext import webapp class Page2(webapp.RequestHandler): def get(self): self.response.out.write("Page 2") application = webapp.WSGIApplication([ ('/page2/', Page2), ], debug=True) def main(): wsgiref.handlers.CGIHandler().run(application) if __name__ == '__main__': main() Question What are the benefits and drawbacks of each pattern? Is one much faster than the other?

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  • Access-specifiers are not foolproof?

    - by Nawaz
    If I've a class like this, class Sample { private: int X; }; Then we cannot access X from outside, so this is illegal, Sample s; s.X = 10; // error - private access But we can make it accessible without editing the class! All we need to do is this, #define private public //note this define! class Sample { private: int X; }; //outside code Sample s; s.X = 10; //no error! Working code at ideone : http://www.ideone.com/FaGpZ That means, we can change the access-specifiers by defining such macros just before the class definition, or before #include <headerfile.h>, #define public private //make public private //or #define protected private //make protected private //or #define so on Isn't it a problem with C++ (Macros/access-specifiers/whatever)? Anyway, the point of this topic is: Using macros, we can easily violate encapsulation. Access-specifiers are not foolproof! Am I right?

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  • How to append() an element and set its style with css() at the same time with jQuery

    - by Acorn
    I tried: $('#canvas').append('<div class="tile"></div>').css({left: leftPos, top: topPos});, but that sets the style of #canvas rather than the appended element. I then tried: $('#canvas').append(('<div class="tile"></div>').css({left: leftPos, top: topPos}));, but that gives the error "Object <div class="tile"></div> has no method 'css'". How can I add the element and set its style at the same time?

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  • Creating a new object destroys an older object with different name in C++

    - by Mikael
    First question here! So, I am having some problems with pointers in Visual C++ 2008. I'm writing a program which will control six cameras and do some processing on them so to clean things up I have created a Camera Manager class. This class handles all operations which will be carried out on all the cameras. Below this is a Camera class which interacts with each individual camera driver and does some basic image processing. Now, the idea is that when the manager is initialised it creates two cameras and adds them to a vector so that I can access them later. The catch here is that when I create the second camera (camera2) the first camera's destructor is called for some reason, which then disconnects the camera. Normally I'd assume that the problem is somewhere in the Camera class, but in this case everything works perfectly as long as I don't create the camera2 object. What's gone wrong? CameraManager.h: #include "stdafx.h" #include <vector> #include "Camera.h" class CameraManager{ std::vector<Camera> cameras; public: CameraManager(); ~CameraManager(); void CaptureAll(); void ShowAll(); }; CameraManager.cpp: #include "stdafx.h" #include "CameraManager.h" CameraManager::CameraManager() { printf("Camera Manager: Initializing\n"); [...] Camera *camera1 = new Camera(NodeInfo,1, -44,0,0); cameras.push_back(*camera1); // Adding the following two lines causes camera1's destructor to be called. Why? Camera *camera2 = new Camera(NodeInfo,0, 44,0,0); cameras.push_back(*camera2); printf("Camera Manager: Ready\n"); }

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  • How can I hit my database with an AJAX call using javascript?

    - by tmedge
    I am pretty new at this stuff, so bear with me. I am using ASP.NET MVC. I have created an overlay to cover the page when someone clicks a button corresponding to a certain database entry. Because of this, ALL of my code for this functionality is in a .js file contained within my project. What I need to do is pull the info corresponding to my entry from the database itself using an AJAX call, and place that into my textboxes. Then, after the end-user has made the desired changes, I need to update that entry's values to match the input. I've been surfing the web for a while, and have failed to find an example that fits my needs effectively. Here is my code in my javascript file thus far: function editOverlay(picId) { //pull up an overlay $('body').append('<div class="overlay" />'); var $overlayClass = $('.overlay'); $overlayClass.append('<div class="dataModal" />'); var $data = $('.dataModal'); overlaySetup($overlayClass, $data); //set up form $data.append('<h1>Edit Picture</h1><br /><br />'); $data.append('Picture name: &nbsp;'); $data.append('<input class="picName" /> <br /><br /><br />'); $data.append('Relative url: &nbsp;'); $data.append('<input class="picRelURL" /> <br /><br /><br />'); $data.append('Description: &nbsp;'); $data.append('<textarea class="picDescription" /> <br /><br /><br />'); var $nameBox = $('.picName'); var $urlBox = $('.picRelURL'); var $descBox = $('.picDescription'); var pic = null; //this is where I need to pull the actual object from the db //var imgList = for (var temp in imgList) { if (temp.Id == picId) { pic= temp; } } /* $nameBox.attr('value', pic.Name); $urlBox.attr('value', pic.RelativeURL); $descBox.attr('value', pic.Description); */ //close buttons $data.append('<input type="button" value="Save Changes" class="saveButton" />'); $data.append('<input type="button" value="Cancel" class="cancelButton" />'); $('.saveButton').click(function() { /* pic.Name = $nameBox.attr('value'); pic.RelativeURL = $urlBox.attr('value'); pic.Description = $descBox.attr('value'); */ //make a call to my Save() method in my repository CloseOverlay(); }); $('.cancelButton').click(function() { CloseOverlay(); }); } The stuff I have commented out is what I need to accomplish and/or is not available until prior issues are resolved. Any and all advice is appreciated! Remember, I am VERY new to this stuff (two weeks, to be exact) and will probably need highly explicit instructions. BTW: overlaySetup() and CloseOverlay() are functions I have living someplace else. Thanks!

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  • Why would it be necessary to subclass from object in Python?

    - by rmh
    I've been using Python for quite a while now, and I'm still unsure as to why you would subclass from object. What is the difference between this: class MyClass(): pass And this: class MyClass(object): pass As far as I understand, object is the base class for all classes and the subclassing is implied. Do you get anything from explicitly subclassing from it? What is the most "Pythonic" thing to do?

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