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  • Javascript push Object to cookies using JSON

    - by Hunkeone
    Hi All on click button I need to add object to array and then write array to cookies. From the start this array can be not empty so I parse cookie first. function addToBasket(){ var basket = $.parseJSON($.cookie("basket")) if (basket.length==0||!basket){ var basket=[]; basket.push( { 'number' : this.getAttribute('number'), 'type' : this.getAttribute('product') } ); } else{ basket.push( { 'number' : this.getAttribute('number'), 'type' : this.getAttribute('product') } ); } $.cookie("basket", JSON.stringify(basket)); } And HTML <button type="button" class="btn btn-success btn-lg" number="12" product="accs" onclick="addToBasket()">Add</button> Unfortunately I'm getting Uncaught ReferenceError: addToBasket is not defined onclick. Can't understand what am I doing wrong? Thanks!

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  • How can I use Object Oriented Javascript to interact with HTML Objects

    - by Steve
    I am very new to object orientated javascript, with experience writing gui's in python and java. I am trying to create html tables that I can place in locations throughout a webpage. Each html table would have two css layouts that control if it is selected or not. I can write all of the interaction if I only have one table. It gets confusing when I have multiple tables. I am wondering how to place these tables throughout a blank webpage and then access the tables individually. I think I am having trouble understanding how inheritance and hierarchy works in javascript/html. NOTE: I am not asking how to make a table. I am trying to dynamically create multiple tables and place them throughout a webpage. Then access their css independently and change it (move them to different locations or change the way the look, independently of the other tables).

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  • C++ object in memory

    - by Neo_b
    Hello. Is there a standard in storing a C++ objects in memory? I wish to set a char* pointer to a certain address in memory, so that I can read certain objects' variables directly from the memory byte by byte. When I am using Dev C++, the variables are stored one by one right in the memory address of an object in the order that they were defined. Now, can it be different while using a different compiler (like the variables being in a different order, or somewhere else)? Thank you in advance. :-)

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  • Is there an ORM with APIs to be used programatically?

    - by Kabeer
    Hello. Neither did not get any response for my previous question, nor enough views :) So here I am now framing my query afresh. Is there any ORM that offers APIs to be used programatically? In my situation, a user will be helped through a wizard to define some entities. Thereafter those entites will be created in a database in form of tables (there will of course be some improvization). I need an ORM that offers APIs for modeling and creating entities during application runtime and not just during design time. Mine is a .Net application, therefore I was looking at Entity Framework. However, to me it looked tied to Visual Studio (I may be wrong also as I am new to it). Any recommendations? Or alternative point of view?

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  • Basic class returns object reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... What I want is the MySQL row array from the mysql_fetch_row() - How do I return the array? What am I missing?

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  • How do I add an object to a binary tree based on the value of a member variable?

    - by Max
    How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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  • sqlite COUNT in flex returning [object Object]

    - by Adam
    I'm sure this is an easy questions and I'm just doing something stupid but I'm really new to all this code. I'm trying to run a sqlite query in flex to count the total number of records I believe its working fine but I just can't figure out how to display the results - all I get back is [object Object]. private function overviewOne():void{ var stmt:SQLStatement = new SQLStatement(); stmt.sqlConnection = sqlConn; stmt.text = "SELECT COUNT(user_id) FROM tbl_user WHERE status_status ='Away'"; stmt.execute(); var result:SQLResult = stmt.getResult(); acoverviewOne = new Array(result.data); trace (result.data[0]); }

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  • Convert Object Hierachey to Object Array

    - by Killercam
    All, I want to create an object array foo[], where the constructor for Foo is public Foo(string name, string discription){} I have a database object which has a structure (not incuding stored procedures, functions or views for simplicity) like public class Database { public string name { get; set; } public string filename { get; set; } public List<Table> tables { get; set; } public Database(string name, string filename) { this.name = name; this.filename = filename; } } protected internal class Table { public string name { get; set; } public List<Column> columns { get; set;} public Table(string name, List<Column> columns) { this.name = name; this.columns = columns; } } protected internal class Column { public string name { get; set; } public string type { get; set; } public Column(string name, string type, int maxLength, bool isNullable) { this.name = name; this.type = type; } } I would like to know the quickest way to add Column and Table information to the Foo[] object array? Clearly I can do List<Foo> fooList = new List<Foo>(); foreach (Table t in database.tables) { fooList.Add(new Foo(t.Name, "Some Description")); foreach (Column c in t.columns) fooList.Add(new Foo(c.Name, "Some Description")); } Foo[] fooArr = fooList.ToArray<Foo>(); But is there a quicker way? Clearly LINQ is likely to be slower for a query that does a simalar operation, but I care allot about speed here so any advice would be appreciated. Perhaps the use of a HashSet would be the way to go as there will not be duplicate entries... Thanks for your time.

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  • Switch Case on type of object (C#)

    - by Sem Dendoncker
    If you want to switch a type of object, what is the best way to do this? ex: private int GetNodeType(NodeDTO node) { switch (node.GetType()) { case typeof(CasusNodeDTO): return 1; case typeof(BucketNodeDTO): return 3; case typeof(BranchNodeDTO): return 0; case typeof(LeafNodeDTO): return 2; default: return -1; } } I know this doesn't work that way, but I was wondering how you could solve this. Is an if then else else else statement appropriate in this case? Or do you use this switch and add .ToString() to the types? Kind regards, Sem

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  • Iterating through a JSON object.

    - by user327508
    [ { "title": "Baby (Feat. Ludacris) - Justin Bieber", "description": "Baby (Feat. Ludacris) by Justin Bieber on Grooveshark", "link": "http://listen.grooveshark.com/s/Baby+Feat+Ludacris+/2Bqvdq", "pubDate": "Wed, 28 Apr 2010 02:37:53 -0400", "pubTime": 1272436673, "TinyLink": "http://tinysong.com/d3wI", "SongID": "24447862", "SongName": "Baby (Feat. Ludacris)", "ArtistID": "1118876", "ArtistName": "Justin Bieber", "AlbumID": "4104002", "AlbumName": "My World (Part II);\nhttp://tinysong.com/gQsw", "LongLink": "11578982", "GroovesharkLink": "11578982", "Link": "http://tinysong.com/d3wI" }, { "title": "Feel Good Inc - Gorillaz", "description": "Feel Good Inc by Gorillaz on Grooveshark", "link": "http://listen.grooveshark.com/s/Feel+Good+Inc/1UksmI", "pubDate": "Wed, 28 Apr 2010 02:25:30 -0400", "pubTime": 1272435930 } ] That is the current JSON object I have. I am now trying to iterate through it to get the import stuff like title and link. This is where I am having trouble I cant seem to get to the content that is past the ":" i tried doing dictionary way couldn't get it. def getLastSong(user,limit): base_url = 'http://gsuser.com/lastSong/' user_url = base_url + str(user) + '/' + str(limit) + "/" raw = urllib.urlopen(user_url) json_raw= raw.readlines() json_object = json.loads(json_raw[0]) #filtering and making it look good. gsongs = [] print json_object for song in json_object[0]: print song This code prints all the information before ":" Please help. ignore the Justin Bieber track :)

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  • javascript using 'this' in global object

    - by Marco Demaio
    What does 'this' keyword refer to when used in gloabl object? Let's say for instance we have: var SomeGlobalObject = { rendered: true, show: function() { /* I should use 'SomeGlobalObject.rendered' below, otherwise it won't work when called from event scope. But it works when called from timer scope!! How can this be? */ if(this.rendered) alert("hello"); } } Now if we call in an inline script in the HTML page: SomeGlobalObject.show(); window.setTimeout("Msg.show()", 1000); everything work ok. But if we do something like AppendEvent(window, 'load', Msg.show); we get an error because this.rendered is undefined when called from the event scope. Do you know why this happens? Could you explain then if there is another smarter way to do this without having to rewrite every time "SomeGlobalObject.someProperty" into the the SomeGlobalObject code? Thanks! AppendEvent is just a simple cross-browser function to append an event, code below, but it does not matter in order to answer the above questions. function AppendEvent(html_element, event_name, event_function) { if(html_element.attachEvent) //IE return html_element.attachEvent("on" + event_name, event_function); else if(html_element.addEventListener) //FF html_element.addEventListener(event_name, event_function, false); }

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  • Javascript error: Object required...tough time fixing this

    - by rtnav2301
    The situation is this: a friend of mine asked me to help her with a website she's working on called www.KeepsakePartyInvitations.com. Her original designer created this code but didn't finish the project. So here I am to help save the day. Now, once a photo has been added to the party template and the mouse is placed over the image, an alternate text message appears to the right. The message informs the visitor how to reposition and resize the image, if necessary. I'm testing the procedure in the invitation to reposition the image. I follow the directions about moving the picture, but the mouse does not let go of the photo. Where ever the mouse moves, so does the image. The same thing occurs if you want to resize the image, you follow the directions but the image does not resize. I check the error message in IE 8 and it states: Message: Object required Line: 873 Char: 3 Code: 0 URI: http://www.keepsakepartyinvitations.com/Includes/JCode.js When I checked the Javascript file, the Line 873 states: tempX = e.clientX + document.body.scrollLeft If you review the javascript file, the function where the line is located is called: function getMouseXY(e). Please help me, it has been a long while since I've worked with Javascript and I'm motivated to get this fixed. Thank you!

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  • How to remove an object from the canvas?

    - by Marius Jonsson
    Hello there, I am making this script that will rotate a needle on a tachometer using canvas. I am a newbie to this canvas. This is my code: function startup() { var canvas = document.getElementById('canvas'); var context = canvas.getContext('2d'); var meter = new Image(); meter.src = 'background.png'; var pin = new Image(); pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); for (var frm = 0; frm < 6000; frm++){ var r=frm/1000; //handle here var i=r*36-27; //angle of rotation from value of r and span var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center } } Here is the script in action: http://www.kingoslo.com/instruments/ The problem is, as you can see, that the red needle is not removed beetween each for-loop. What I need to do is to clear the canvas for the pin object between each cycle of the loop. How do I do this? Thanks. Kind regards, Marius

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  • Java: extending Object class

    - by Fabio F.
    Hello, I'm writing (well, completing) an "extension" of Java which will help role programming. I translate my code to Java code with javacc. My compilers add to every declared class some code. Here's an example to be clearer: MyClass extends String implements ObjectWithRoles { //implements... is added /*Added by me */ public setRole(...){...} public ... /*Ends of stuff added*/ ...//myClass stuff } It adds Implements.. and the necessary methods to EVERY SINGLE CLASS you declare. Quite rough, isnt'it? It will be better if I write my methods in one class and all class extends that.. but.. if class already extends another class (just like the example)? I don't want to create a sort of wrapper that manage roles because i don't want that the programmer has to know much more than Java, few new reserved words and their use. My idea was to extends java.lang.Object.. but you can't. (right?) Other ideas? I'm new here, but I follow this site so thank you for reading and all the answers you give! (I apologize for english, I'm italian)

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  • Object Design: How to Organize/Structure a "Collection Class"

    - by CrimsonX
    I'm currently struggling to understand how I should organize/structure a class which I have already created. The class does the following: As its input in the constructor, it takes a collection of logs In the constructor it validates and filters the logs through a series of algorithms implementing my business logic After all filtering and validation is complete, it returns a collection (a List) of the valid and filtered logs which can be presented to the user graphically in a UI. Here is some simplified code describing what I'm doing: class FilteredCollection { public FilteredCollection( SpecialArray<MyLog> myLog) { // validate inputs // filter and validate logs in collection // in end, FilteredLogs is ready for access } Public List<MyLog> FilteredLogs{ get; private set;} } However, in order to access this collection, I have to do the following: var filteredCollection = new FilteredCollection( secialArrayInput ); //Example of accessing data filteredCollection.FilteredLogs[5].MyLogData; Other key pieces of input: I foresee only one of these filtered collections existing in the application (therefore should I make it a static class? Or perhaps a singleton?) Testability and flexibility in creation of the object is important (Perhaps therefore I should keep this an instanced class for testability?) I'd prefer to simplify the dereferencing of the logs if at all possible, as the actual variable names are quite long and it takes some 60-80 characters to just get to the actual data. My attempt in keeping this class simple is that the only purpose of the class is to create this collection of validated data. I know that there may be no "perfect" solution here, but I'm really trying to improve my skills with this design and I would greatly appreciate advice to do that. Thanks in advance.

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  • How to reference var from frame on timeline in an object class

    - by brybam
    I'm using Flash Professional cs5/AS3 I'll try and describe this the best I can. I'm new to ActionScript. So, in my timeline I have a var on a frame that represents "lives" and i have some code in the timeline that takes down the number of lives depending on certain events, which all works great. so, now i wanted to make a constructor class that I could reuse for a bunch of movie clip objects and I only want these objects to be able to move if the lives variable is greater than certain number. So now, building my constructor class for these objects i just wanted put an if statement that is looking to see if the lives are greater than a certain number, which if it is then should make these objects do what i want...But, when i run the project I get "1120: Access of undefined property lives." lives is the var I made obviously like I said, and it works fine being referenced everyone else except when I make a new .as file for these objects then try and reference it. I get the same error when I try and establish "lives" in the main project class too. I'm not sure where I should put this var or how I can make it so i can reference it from an object class. I'm not really sure how to word or describe my issue which has made it hard to search for a tutorial. Any suggestions i'm sure this has to be a simple task.

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  • Javascript object binding problem inside of function prototype definitions

    - by Arion
    Hi all, I am trying to figure out the right place to bind a function prototype to be called later. The full code of the example can be found here: http://www.iprosites.com/jso/ My javascript example is very basic: function Obj(width, height){ this.width = width; this.height = height; } Obj.prototype.test = function(){ var xhr=init(); xhr.open('GET', '?ajax=test', true); xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8'); xhr.onreadystatechange = function() { if (xhr.responseText == '403') { window.location.reload(false); } if (xhr.readyState == 4 && xhr.status == 200) { this.response = parseResponse(xhr.responseText); document.getElementById('resp').innerHTML = this.response.return_value; this.doAnotherAction(); } }; xhr.send(); } Obj.prototype.doAnotherAction = function(){ alert('Another Action Done'); } var myo = new Obj(4, 6); If you try to run myo.test() in Firebug, you will get the "this.doAnotherAction is not a function" response. The 2 support functions init() and parseResponse() can be found in the test.js link if you wish to view them, but should not be too relevant to this problem. I've affirmed that this.doAnotherAction() thinks "this" is the XMLHttpResponse object as expected from an instanceof test. Can anyone help with some insight on direction with binding? Everything I've tried seems not to work! I do use Mootools, although the library is not present in this example. Thanks in advance, Arion

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  • C#: An object reference is required for the non-static field, method, or Property

    - by Omin
    I feel bad for asking this when there are so many questions that are related but I was not able to find/understand the answer I am looking for. // 2. Develop a program to convert currency X to currency Y and visa versa. using System; class Problem2 { static void Main (string[] args) { while (true) { Console.WriteLine ("1. Currency Conversion from CAD to Won"); Console.WriteLine ("2. Currency Conversion from Won to Cad"); Console.Write ("Choose from the Following: (1 or 2)? "); int option = int.Parse( Console.ReadLine() ); //double x; if (option == 1) { Console.WriteLine ("Type in the amount you would like to Convert CAD to Won: "); //double y =double.Parse( Console.ReadLine()); //Console.WriteLine( cadToWon( y ) ); Console.WriteLine( cadToWon( double.Parse( Console.ReadLine() ) )); } if (option == 2) { Console.WriteLine ("Type in the amount you would like to Convert Won to CAD: "); Console.WriteLine( wonToCad (double.Parse( Console.ReadLine()))); } } } double cadToWon( double x ) { return x * 1113.26; } double wonToCad( double x) { return x / 1113.26; } } This give me the Error messgae "An object reference is required for the non-static field, method, or property 'Problem2..." I know that I'll be able to run the program if I add static infront of the methods but I'm wondering why I need it (I think it's because Main is static?) and what do I need to change in order to use these methods without adding static to them? Thank you

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  • creating an object within a function of a program

    - by user1066524
    could someone please tell me what I need to do in order to create an object in a function. I will try to explain by making up some sort of example... Let's say I have a program named TimeScheduler.cpp that implements the class Schedule.h (and I have the implementation in a separate file Schedule.cpp where we define the methods). In the declaration file we have declared two constructors Schedule(); //the default and Schedule(int, int, int);//accepts three arguments to get to the point--let's say in the main program file TimeScheduler.cpp we created our own functions in this program apart from the functions inherited from the class Schedule. so we have our prototypes listed at the top. /*prototypes*/ void makeSomeTime(); etc..... we have main(){ //etc etc... } we then define these program functions void makeSomeTime(){ //process } let's say that inside the function makeSomeTime(), we would like to create an array of Schedule objects like this Schedule ob[]={ summer(5,14, 49), fall(9,25,50) }; what do I have to do to the function makeSomeTime() in order for it to allow me to create this array of objects. The reason I ask is currently i'm having difficulty with my own program in that it WILL allow me to create this array of objects in main()....but NOT in a function like I just gave an example of. The strange thing is it will allow me to create a dynamic array of objects in the function..... like Schedule *ob = new Schedule[n+1]; ob[2]= Schedule(x,y,z); Why would it let me assign to a non-dynamic array in main(), but not let me do that in the function?

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  • Object Reference with TimeSpan/DateTime

    - by user1732039
    When creating an appointment i want to send an email out to the patient with details like Time, Date etc. I know the email service i have created works (i have tested it by hardcoding strings into the method with the problem. The Problem is that i am getting Object reference issues with converting the Time and Date to a string. It does create the appointment data in the database correctly (time and date). User_Doctor thisDoc = user_DoctorComboBox.SelectedItem as User_Doctor; User_Patient thisPatient = appointment_Patient_autoComplete.SelectedItem as User_Patient; Appointment App = AppointmentSlots.SelectedItem as Appointment; DateTime date = (DateTime)datePickerAppointment.SelectedDate; TimeSpan timeslot = App.Time; //For Emailing Patients string fullname = thisPatient.PatientName + " " + thisPatient.PatientSurname; string mestime = timeslot.ToString("HH:mm"); string mesdate = date.ToString("MM/dd/yyyy"); string email = thisPatient.aspnet_Users.aspnet_Membership.LoweredEmail; EmailServiceClient em = new EmailServiceClient(); em.createMessageAsync(email, "Upcomming Appointment", fullname, mestime, mesdate, thisDoc.aspnet_Users.UserName, true); The problem occures with the strings mestime and mesdate, as well as with getting the email of the user from the database (again this exists in the db, as a nvar)

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  • Design pattern for window management in a Java Swing app

    - by Lord Torgamus
    I've just started creating my very first little Java Swing app. When the program opens, it brings up a single, simple window with a label and a couple buttons. Clicking one of those buttons is supposed to wipe out the welcome screen and replace it with a totally different panel. I'm not sure what the best way to create that functionality is. One method would be to pass my JFrame as an argument into... just about every other component, but that feels hacky to me. Or, there's making each panel double as an action listener, but that doesn't seem right, either. Is there a design pattern I should be applying here? "Replace the contents of the main — and only — window" must be a reasonably common operation. A name for the pattern would be enough; I can use Google on my own from there. (I wouldn't say no to a longer explanation, though.)

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  • Understanding C# async / await (2) Awaitable / Awaiter Pattern

    - by Dixin
    What is awaitable Part 1 shows that any Task is awaitable. Actually there are other awaitable types. Here is an example: Task<int> task = new Task<int>(() => 0); int result = await task.ConfigureAwait(false); // Returns a ConfiguredTaskAwaitable<TResult>. The returned ConfiguredTaskAwaitable<TResult> struct is awaitable. And it is not Task at all: public struct ConfiguredTaskAwaitable<TResult> { private readonly ConfiguredTaskAwaiter m_configuredTaskAwaiter; internal ConfiguredTaskAwaitable(Task<TResult> task, bool continueOnCapturedContext) { this.m_configuredTaskAwaiter = new ConfiguredTaskAwaiter(task, continueOnCapturedContext); } public ConfiguredTaskAwaiter GetAwaiter() { return this.m_configuredTaskAwaiter; } } It has one GetAwaiter() method. Actually in part 1 we have seen that Task has GetAwaiter() method too: public class Task { public TaskAwaiter GetAwaiter() { return new TaskAwaiter(this); } } public class Task<TResult> : Task { public new TaskAwaiter<TResult> GetAwaiter() { return new TaskAwaiter<TResult>(this); } } Task.Yield() is a another example: await Task.Yield(); // Returns a YieldAwaitable. The returned YieldAwaitable is not Task either: public struct YieldAwaitable { public YieldAwaiter GetAwaiter() { return default(YieldAwaiter); } } Again, it just has one GetAwaiter() method. In this article, we will look at what is awaitable. The awaitable / awaiter pattern By observing different awaitable / awaiter types, we can tell that an object is awaitable if It has a GetAwaiter() method (instance method or extension method); Its GetAwaiter() method returns an awaiter. An object is an awaiter if: It implements INotifyCompletion or ICriticalNotifyCompletion interface; It has an IsCompleted, which has a getter and returns a Boolean; it has a GetResult() method, which returns void, or a result. This awaitable / awaiter pattern is very similar to the iteratable / iterator pattern. Here is the interface definitions of iteratable / iterator: public interface IEnumerable { IEnumerator GetEnumerator(); } public interface IEnumerator { object Current { get; } bool MoveNext(); void Reset(); } public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IDisposable, IEnumerator { T Current { get; } } In case you are not familiar with the out keyword, please find out the explanation in Understanding C# Covariance And Contravariance (2) Interfaces. The “missing” IAwaitable / IAwaiter interfaces Similar to IEnumerable and IEnumerator interfaces, awaitable / awaiter can be visualized by IAwaitable / IAwaiter interfaces too. This is the non-generic version: public interface IAwaitable { IAwaiter GetAwaiter(); } public interface IAwaiter : INotifyCompletion // or ICriticalNotifyCompletion { // INotifyCompletion has one method: void OnCompleted(Action continuation); // ICriticalNotifyCompletion implements INotifyCompletion, // also has this method: void UnsafeOnCompleted(Action continuation); bool IsCompleted { get; } void GetResult(); } Please notice GetResult() returns void here. Task.GetAwaiter() / TaskAwaiter.GetResult() is of such case. And this is the generic version: public interface IAwaitable<out TResult> { IAwaiter<TResult> GetAwaiter(); } public interface IAwaiter<out TResult> : INotifyCompletion // or ICriticalNotifyCompletion { bool IsCompleted { get; } TResult GetResult(); } Here the only difference is, GetResult() return a result. Task<TResult>.GetAwaiter() / TaskAwaiter<TResult>.GetResult() is of this case. Please notice .NET does not define these IAwaitable / IAwaiter interfaces at all. As an UI designer, I guess the reason is, IAwaitable interface will constraint GetAwaiter() to be instance method. Actually C# supports both GetAwaiter() instance method and GetAwaiter() extension method. Here I use these interfaces only for better visualizing what is awaitable / awaiter. Now, if looking at above ConfiguredTaskAwaitable / ConfiguredTaskAwaiter, YieldAwaitable / YieldAwaiter, Task / TaskAwaiter pairs again, they all “implicitly” implement these “missing” IAwaitable / IAwaiter interfaces. In the next part, we will see how to implement awaitable / awaiter. Await any function / action In C# await cannot be used with lambda. This code: int result = await (() => 0); will cause a compiler error: Cannot await 'lambda expression' This is easy to understand because this lambda expression (() => 0) may be a function or a expression tree. Obviously we mean function here, and we can tell compiler in this way: int result = await new Func<int>(() => 0); It causes an different error: Cannot await 'System.Func<int>' OK, now the compiler is complaining the type instead of syntax. With the understanding of the awaitable / awaiter pattern, Func<TResult> type can be easily made into awaitable. GetAwaiter() instance method, using IAwaitable / IAwaiter interfaces First, similar to above ConfiguredTaskAwaitable<TResult>, a FuncAwaitable<TResult> can be implemented to wrap Func<TResult>: internal struct FuncAwaitable<TResult> : IAwaitable<TResult> { private readonly Func<TResult> function; public FuncAwaitable(Func<TResult> function) { this.function = function; } public IAwaiter<TResult> GetAwaiter() { return new FuncAwaiter<TResult>(this.function); } } FuncAwaitable<TResult> wrapper is used to implement IAwaitable<TResult>, so it has one instance method, GetAwaiter(), which returns a IAwaiter<TResult>, which wraps that Func<TResult> too. FuncAwaiter<TResult> is used to implement IAwaiter<TResult>: public struct FuncAwaiter<TResult> : IAwaiter<TResult> { private readonly Task<TResult> task; public FuncAwaiter(Func<TResult> function) { this.task = new Task<TResult>(function); this.task.Start(); } bool IAwaiter<TResult>.IsCompleted { get { return this.task.IsCompleted; } } TResult IAwaiter<TResult>.GetResult() { return this.task.Result; } void INotifyCompletion.OnCompleted(Action continuation) { new Task(continuation).Start(); } } Now a function can be awaited in this way: int result = await new FuncAwaitable<int>(() => 0); GetAwaiter() extension method As IAwaitable shows, all that an awaitable needs is just a GetAwaiter() method. In above code, FuncAwaitable<TResult> is created as a wrapper of Func<TResult> and implements IAwaitable<TResult>, so that there is a  GetAwaiter() instance method. If a GetAwaiter() extension method  can be defined for Func<TResult>, then FuncAwaitable<TResult> is no longer needed: public static class FuncExtensions { public static IAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { return new FuncAwaiter<TResult>(function); } } So a Func<TResult> function can be directly awaited: int result = await new Func<int>(() => 0); Using the existing awaitable / awaiter - Task / TaskAwaiter Remember the most frequently used awaitable / awaiter - Task / TaskAwaiter. With Task / TaskAwaiter, FuncAwaitable / FuncAwaiter are no longer needed: public static class FuncExtensions { public static TaskAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { Task<TResult> task = new Task<TResult>(function); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter<TResult>. } } Similarly, with this extension method: public static class ActionExtensions { public static TaskAwaiter GetAwaiter(this Action action) { Task task = new Task(action); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter. } } an action can be awaited as well: await new Action(() => { }); Now any function / action can be awaited: await new Action(() => HelperMethods.IO()); // or: await new Action(HelperMethods.IO); If function / action has parameter(s), closure can be used: int arg0 = 0; int arg1 = 1; int result = await new Action(() => HelperMethods.IO(arg0, arg1)); Using Task.Run() The above code is used to demonstrate how awaitable / awaiter can be implemented. Because it is a common scenario to await a function / action, so .NET provides a built-in API: Task.Run(): public class Task2 { public static Task Run(Action action) { // The implementation is similar to: Task task = new Task(action); task.Start(); return task; } public static Task<TResult> Run<TResult>(Func<TResult> function) { // The implementation is similar to: Task<TResult> task = new Task<TResult>(function); task.Start(); return task; } } In reality, this is how we await a function: int result = await Task.Run(() => HelperMethods.IO(arg0, arg1)); and await a action: await Task.Run(() => HelperMethods.IO());

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  • Design pattern for animation sequence in LibGDX

    - by kevinyu
    What design pattern to use for sequence of animation that involve different actor in libGDX. For example I am making a game to choose a wolf from a group of sheeps. The first animation played when the game begin is the wolf enter the field that is filled with two sheeps.Then the wolf disguise as a sheep and goes to the center of the screen. Then the game will shuffle the sheeps. After it finished it will ask the player where is the wolf. The game wait for player input. After that the game will show animation to show the player whether their answer is right or wrong. I am currently using State design pattern. There are four states wolfEnterState,DisguiseState,ShuffleState,UserInputState, and answerAnimationState. I feel that my code is messy. I use addAction with action sequence and action completion(new Runnable()) a lot. I feel that the action sequence is getting long. Is there a better solution for this kind of problem

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  • Am I missing a pattern?

    - by Ryan Pedersen
    I have a class that is a singleton and off of the singleton are properties that hold the instances of all the performance counters in my application. public interface IPerformanceCounters { IPerformanceCounter AccountServiceCallRate { get; } IPerformanceCounter AccountServiceCallDuration { get; } Above is an incomplete snippet of the interface for the class "PerformanceCounters" that is the singleton. I really don't like the plural part of the name and thought about changing it to "PerformanceCounterCollection" but stopped because it really isn't a collection. I also thought about "PerformanceCounterFactory" but it is really a factory either. After failing with these two names and a couple more that aren't worth mentioning I thought that I might be missing a pattern. Is there a name that make sense or a change that I could make towards a standardized pattern that would help me put some polish on this object and get rid of the plural name? I understand that I might be splitting hairs here but that is why I thought that the "Programmers" exchange was the place for this kind of thing. If it is not... I am sorry and I will not make that mistake again. Thanks!

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