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  • Objective-C Objects Having Each Other as Properties

    - by mwt
    Let's say we have two objects. Furthermore, let's assume that they really have no reason to exist without each other. So we aren't too worried about re-usability. Is there anything wrong with them "knowing about" each other? Meaning, can each one have the other as a property? Is it OK to do something like this in a mythical third class: Foo *f = [[Foo alloc] init]; self.foo = f; [f release]; Bar *b = [[Bar alloc] init]; self.bar = b; [b release]; foo.bar = bar; bar.foo = foo; ...so that they can then call methods on each other? Instead of doing this, I'm usually using messaging, etc., but sometimes this seems like it might be a tidier solution. I hardly ever see it in example code (maybe never), so I've shied away from doing it. Can somebody set me straight on this? Thanks.

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  • Want to understand C++ sentry object

    - by Romain Hippeau
    I answered this [question][1] and somebody else had answered as he modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? [1]: http://stackoverflow.com/questions/2688043/call-return-feature-of-classic-cc-with-classes-what-modern-languages-have-it/2688095#2688095 /

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  • What object called a method in Obj-C

    - by Loz
    Hi, I am looking to write a plugin controller in Cocoa that loads bundles, and exposes a specific set of methods for the plugins to call. My question is this: is it possible to know (any) info about the object that called a method in the controller. When an instantiated plugin calls a method in my plugin controller, I would like to know which of the plugin instances called the method, without having to rely on the plugin sending a pointer to itself as a parameter (I could always validate the pointer they send, but I want to keep the API methods as simple as possible). There may be no perfect solution (and there are simple workarounds), but it's always good to learn some new tricks if possible (or the reasons why it's impossible). Thanks in advance.

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  • In need of a good MATLAB class tutorial

    - by rlbond
    I'm having a lot of trouble trying to figure out how to use classes in MATLAB. I'm very familiar with C++ and Python but I just can't figure anything out about how to define classes in MATLAB. Does anyone know a very good resource with lots of examples? The official documentation leaves much to be desired.

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  • How do I make JavaScript to set these element values?

    - by dmanexe
    I have two fields that need to multiply each other and fill a 3rd form's value. Here's the HTML: <input type="text" name="estimate[concrete][price]" value="" onBlur="calc_concreteprice(document.forms.mainform);" /> per SF <strong>times</strong> <input type="text" name="estimate[concrete][sqft]" value="" onBlur="calc_concreteprice(document.forms.mainform);" /> SF = <input type="text" name="estimate[concrete][quick_total]" value="" /> Here's my JavaScript: function calc_concreteprice(mainform) { var oprice; var ototal; oprice = ((mainform.estimate[concrete][sqft].value) * (mainform.estimate[concrete][price].value)); ototal = (oprice); mainform.estimate[concrete][quick_total].value = ototal; } I want the first two forms to be multiplied together and output to the third. I think my problem may be within how I am referencing the input field names, with brackets (I'm taking results from this form as an array so I'm already used to working with the results as a multi-dimensional array). Thanks for the help!

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  • What would be a good starting point for development of a 3D application for representation of struct

    - by Lela Dax
    I was thinking QT on OpenGL. Multiplatform ability and being able to be closed (at no cost) at a later point would be important points. But I'm very interested in finding a way that is not only viable but also has the least amount of reinvention of the wheel. e.g. "Why not Ogre? A ready powerful 3D engine without reinventing that part". But I'm very uncertain in what is the optimal collection of tools for that job.

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  • ado.net data entity problem

    - by ognjenb
    I have this error Cannot implicitly convert type 'System.Linq.IQueryable' to 'Mvc.Models.engineer'. An explicit conversion exists (are you missing a cast?) after write this code engineer Ing = new engineer(); Ing = from j in testPersons.ibekoengineer select j.Name; What is wrong?

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  • Usage patterns/use cases for DI or when to start using it

    - by Fabian
    I'm not sure for which use cases one should to use DI in the application. I know that injecting services like PlaceService or CalculationService etc fits very well but should I also create my domain objects with DI like a User? What is if the User has only one constructor which requires a first and lastname. Is this solveable with DI? Should I use DI to create the instances for Set/List interfaces or is this pure overkill? I use guice primarily.

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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • when to make a method static

    - by Don
    Hi, I'd like to know how people decide whether to define a method as static. I'm aware that a method can only be defined as static if it doesn't require access to instance fields. So lets say we have a method that does not access instance fields, do you always define such a method as static, or only if you need to call it statically (without a reference to an instance). Perhaps another way of asking the same question, is whether you use static or non-static as the default? Thanks, Don

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  • How to check if canvas objects overlap each other

    - by ?????? ???????
    I'm trying to check if two objects (e.g. a rectangle and a triangle) on a HTML5 canvas are overlapping each other. Currently I can only check that by looking at the screen (having set globalCompositeOperation='lighter'). My first idea would have been to scan all over the canvas if the "lighter" (compare code snippet above) color exists in the canvas. But therefor I would have to look at every single pixel which was rather costly for what I need. Is there a (better) alternative to automatically check if they are overlapping? Best regards.

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  • When to define SDD(System Sequence Diagram) operations System->Actor?

    - by devoured elysium
    I am having some trouble understanding how to make System Sequence Diagrams, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: Let's assume the System is a Cinema Ticket Store and the Actor is a client that wants to buy a ticket. 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The User tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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  • PHP Store User Data without Sessions

    - by Sev
    Is there anyway to store users data such as userid, email, etc to be accessible from all pages of a website after they have logged in, but without using sessions or cookies? For example: class User { var $userid; var $username; var $email; .. methods.. } after they login at login.php $currentUser = new User($_POST['username']) now, how do I access $currentUser from another page, such as index.php if I shouldn't use sessions or cookies at all? so that I could do the following in index.php: if ($currentUser->userid > -1) { echo "you are logged in as: " . $currentUser->username; } else { echo "click here to login"; } i asked a similar question before, here, but the answers didn't fulfill my needs.

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  • jQuery - now: Creating an object and storing values in it to pass to an AJAX call

    - by Josh K
    I have an array: myarr = []; I'm filling it with some values: myarray['name'] = "Me!"; Now I want to transform that array into a set of Key = Value pairs. I though jQuery would do it automatically, but it doesn't seem to. $.ajax ({ type: "POST", dataType: "text", url: "myurl", data: myarr }); Is there a way to do this or something I'm doing wrong? I get no javascript errors, and no serverside errors other then no POST information at all. I need the request to be sent as a true POST request. I need to keep the php code simple because sometimes the login won't be an AJAX call. I'm now trying the following with an error unexepected token ':' myarr: { 'name':'me' } The question has now become: How do I initialize a new javascript object as "blank", how do I set up mappings, and how do I pass it in an AJAX call?

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  • PHP Changing Class Variables Outside of Class

    - by Jamie Bicknell
    Apologies for the wording on this question, I'm having difficulties explaining what I'm after, but hopefully it makes sense. Let's say I have a class, and I wish to pass a variable through one of it's methods, then I have another method which outputs this variable. That's all fine, but what I'm after is that if I update the variable which was originally passed, and do this outside the class methods, it should be reflected in the class. I've created a very basic example: class Test { private $var = ''; function setVar($input) { $this->var = $input; } function getVar() { echo 'Var = ' . $this->var . '<br />'; } } If I run $test = new Test(); $string = 'Howdy'; $test->setVar($string); $test->getVar(); I get Var = Howdy However, this is the flow I would like: $test = new Test(); $test->setVar($string); $string = 'Hello'; $test->getVar(); $string = 'Goodbye'; $test->getVar(); Expected output to be Var = Hello Var = Goodbye I don't know what the correct naming of this would be, and I've tried using references to the original variable but no luck. I've come across this in the past, with the PDO prepared statements, see Example #2 $stmt = $dbh->prepare("INSERT INTO REGISTRY (name, value) VALUES (?, ?)"); $stmt->bindParam(1, $name); $stmt->bindParam(2, $value); // insert one row $name = 'one'; $value = 1; $stmt->execute(); // insert another row with different values $name = 'two'; $value = 2; $stmt->execute(); I know I can change the variable to public and do the following, but it isn't quite the same as how the PDO class handles it, and I'm really looking to mimic that behaviour. $test = new Test(); $test->setVar($string); $test->var = 'Hello'; $test->getVar(); $test->var = 'Goodbye'; $test->getVar(); Any help, ideas, pointers, or advice would be greatly appreciated, thanks.

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  • Best ways to construct Dynamic Search Conditions for Sql

    - by CoolBeans
    I have always wondered what's the best way to achieve this task. In most web based applications you have to provide search options on many different criteria. Based on what criteria is chosen behind the scene you modify your SQL. Generally, this is how I tend to go about it:- Have a base SQL template. In the base template have conditions like this WHERE [#PRE_COND1] AND [#PRE_COND2] .. so on and so forth. So an example SQL might look something like SELECT NAME,AGE FROM PERSONS [,#TABLE2] [,#TABLE3] WHERE [#PRE_COND1] AND [#PRE_COND2] ORDER BY [#ORD_COND1] AND [#ORD_COND2] etc. During run time after figuring out the all the search criteria user has entered, I replace the [#PRE_COND1]s and [#ORD_COND1]s with the appropriate SQLs and then execute the query. I personally do not like this brute force method. However, I never came across a better approach either. How do you accomplish such tasks generally given you are either using native JDBC or Spring JDBC? It is almost like I need a C MACRO like functionality in Java to do this.

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  • Passing arguments between classes - use public properties or pass a properties class as argument?

    - by devoured elysium
    So let's assume I have a class named ABC that will have a list of Point objects. I need to make some drawing logic with them. Each one of those Point objects will have a Draw() method that will be called by the ABC class. The Draw() method code will need info from ABC class. I can only see two ways to make them have this info: Having Abc class make public some properties that would allow draw() to make its decisions. Having Abc class pass to draw() a class full of properties. The properties in both cases would be the same, my question is what is preferred in this case. Maybe the second approach is more flexible? Maybe not? I don't see here a clear winner, but that sure has more to do with my inexperience than any other thing. If there are other good approaches, feel free to share them. Here are both cases: class Abc1 { public property a; public property b; public property c; ... public property z; public void method1(); ... public void methodn(); } and here is approach 2: class Abc2 { //here we make take down all properties public void method1(); ... public void methodn(); } class Abc2MethodArgs { //and we put them here. this class will be passed as argument to //Point's draw() method! public property a; public property b; public property c; ... public property z; } Also, if there are any "formal" names for these two approaches, I'd like to know them so I can better choose the tags/thread name, so it's more useful for searching purposes. That or feel free to edit them.

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  • Persistance Queue Implementation

    - by Winter
    I was reading an article on Batch Processing in java over at JDJ http://java.sys-con.com/node/415321 . The article mentioned using a persistence queue as a Batch Updater instead of immediately sending an individual insert or update to the database. The author doesn't give a concrete example of this concept so I googled Persistence Queue but that didn't come up with much. Does anyone know of a good example of this?

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  • Possible to add an EventListener to a function for Actionscript 3?

    - by Tom
    I'm trying to setup something like Aspect Oriented Programming in Actionscript 3, basically the only thing I need to be able to do is something like this: SomeClass.getMethod("methodName").addEventListener(afterMethodExecuted, function() { //run code }); This way I can run code after (or before) any method in any class has run, allowing numerous new possibilities. How should I implement this?

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  • Why can't I create an abstract constructor on an abstract C# class?

    - by Anthony D
    I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one. public abstract class A { abstract A(int a, int b); } However I get a message saying the abstract modifier is invalid on this item. My goal was to force some code like this. public class B : A { public B(int a, int b) : base(a, b) { //Some other awesome code. } } This is all C# .NET code. Can anyone help me out? Update 1 I wanted to add some things. What I ended up with was this. private A() { } protected A(int a, int b) { //Code } That does what some folks are saying, default is private, and the class needs to implement a constructor. However that doesn't FORCE a constructor with the signature A(int a, int b). public abstract class A { protected abstract A(int a, int b) { } } Update 2 I should be clear, to work around this I made my default constructor private, and my other constructor protected. I am not really looking for a way to make my code work. I took care of that. I am looking to understand why C# does not let you do this.

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  • Class architecture, no friends allowed

    - by Captain Comic
    The question of why there are no friends in C# has been extensively discussed. I have the following design problems. I have a class that has only one public function AddOrder(Order ord). Clients are allowed to call only this function. All other logic must be hidden. Order class is listening to market events and must call other other function of TradingSystem ExecuteOrder, so I have to make it public as well. Doing that I will allow clients of Trading system to call this function and I don't want that. class TradingSystem { // Trading system stores list of orders List<Order> _orders; // this function is made public so that Order can call ir public ExecuteOrder(Order ord) { } // this function is made public for external clients public AddOrder(OrderRequest ordreq) { // create order and pass it this order.OnOrderAdded(this); } } class Order { TradingSystem _ts; public void OnOrderAdded(TradingSystem ts) { _ts = ts; } void OnMarketEvent() { _ts.ExecuteOrder() } }

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  • Entity Framework 4 - Delete Object

    - by GibboK
    I have 3 Tables in my DataBase CmsMasterPages CmsMasterPagesAdvSlots (Pure Juction Table) CmsAdvSlots Here a Picture of my EDM: I need find out all objects CmsAdvSlot connected with a CmsMasterPage (it is working in my code posted belove), and DELETE the result (CmsAdvSlot) from the DataBase. My Problem is I am not able to DELETE this Objects when I found theme. Error: The object cannot be deleted because it was not found in the ObjectStateManager. int findMasterPageId = Convert.ToInt32(uxMasterPagesListSelector.SelectedValue); CmsMasterPage myMasterPage = context.CmsMasterPages.FirstOrDefault(x => x.MasterPageId == findMasterPageId); var resultAdvSlots = myMasterPage.CmsAdvSlots; // It is working until here foreach (var toDeleteAdv in resultAdvSlots) { context.DeleteObject(myMasterPage.CmsAdvSlots.Any()); // ERORR HERE!! context.SaveChanges(); } Any idea how to solve it? Thanks for your time! :-)

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  • Design issue when having classes implement different interfaces to restrict client actions

    - by devoured elysium
    Let's say I'm defining a game class that implements two different views: interface IPlayerView { void play(); } interface IDealerView { void deal(); } The view that a game sees when playing the game, and a view that the dealer sees when dealing the game (this is, a player can't make dealer actions and a dealer can't make player actions). The game definition is as following: class Game : IPlayerView, IDealerView { void play() { ... } void deal() { ... } } Now assume I want to make it possible for the players to play the game, but not to deal it. My original idea was that instead of having public Game GetGame() { ... } I'd have something like public IPlayerView GetGame() { ... } But after some tests I realized that if I later try this code, it works: IDealerView dealerView = (IDealerView)GameClass.GetGame(); this works as lets the user act as the dealer. Am I worrying to much? How do you usually deal with this patterns? I could instead make two different classes, maybe a "main" class, the dealer class, that would act as factory of player classes. That way I could control exactly what I would like to pass on the the public. On the other hand, that turns everything a bit more complex than with this original design. Thanks

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