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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 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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  • 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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  • How can I avoid setting some columns if others haven't changed, when working with Linq To SQL?

    - by Patrick Szalapski
    In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single() row.Name = "Example" ' line 3 dataContext.SubmitChanges() ' line 4 Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query only when necessary--that is, no SQL will be generated if the customer's name was already "Example". So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?

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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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  • 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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  • Trigger on database using a web application and a winform application

    - by Michael
    Hello all, Situation: I have a web application which shows errors and where you can accept those error messages. I also have a service, which checks errors from a system and sets the error messages in the database. When I accept an error in the web application, i would like the service to know which error message has been accepted, so that it can do some other actions. My guess is that this could be done through some sort of trigger, but i can't figure out how. Can anyone help me with this?

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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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  • 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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  • 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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  • Codeigniter Model appending word_limiter to result object

    - by yahyaE
    I have a get_all function in my model class in Codeigniter 2.0+. For a given database field name, i need to use word_limiter() in text helper. In view page, i loop result set as object $row->field_name_to_be_limited. With below code, i am trying to do it. But i should include the change $q->$field_name = word_limiter($q->$field_name, 4); into the $q->result. Thanks for help. function get_all($table_name,$orderByField,$ascDesc,$field_name = '') { $this->load->helper('text'); $qOrder = $this->db->order_by($orderByField,$ascDesc); $q = $this->db->get($table_name,$qOrder); if( ! $field_name ==='') $q->$field_name = word_limiter($q->$field_name, 4); return $q->result(); }

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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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  • Secure way to backup MySQL databases?

    - by user203538
    What is the best/secure way to backup a mysql database on windows server (2008)? I have "MySQL Administrator" but that requires that you save passwords for backup project. I'm not keen on doing as anyone gaining access to the server would then have easy access to the database. Can you do anything similar to SQL Server like using Windows authentication. If not what is the most secure (and practical) way of backups. Lastly, what are the privileges needed to backup a database? I have created a single user just for this task. Please advise.

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  • Best .NET Solution for Frequently Changed Database

    - by sestocker
    I am currently architecting a small CRUD applicaton. Their database is a huge mess and will be changing frequently over the course of the next 6 months to a year. What would you recommend for my data layer: 1) ORM (if so, which one?) 2) Linq2Sql 3) Stored Procedures 4) Parametrized Queries I really need a solution that will be dynamic enough (both fast and easy) where I can replace tables and add/delete columns frequently. Note: I do not have much experience with ORM (only a little SubSonic) and generally tend to use stored procedures so maybe that would be the way to go. I would love to learn Ling2Sql or NHibernate if either would allow for the situation I've described above.

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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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  • Storing an arbitrary R object onto HDD?

    - by Harokitty
    I understand that we can export data matrices to csv or xlsx files. What about complex objects like lm? For example, in my work I might have a list of length 1000, each with a single lm() object. Each time I load R I have to wait a long time to populate the 1000 length list with these lm objects with a for loop or a lapply. I would rather just save the list somewhere on my HDD at the end of a session and open it at the start of the next session.

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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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  • 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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  • PHP: Simulate multiple MySQL connections to same database

    - by Varun
    An insert query is constantly getting logged in my MySQL slow query log. I want to see how much time the INSERT query is taking with 100 simultaneous insert operations(to the same table). So I need to simulate the follwoing. 500 different simultaneous connections from PHP to the same database on a mysql server, all of which are inserting a row(simultaneously) to the same table. DO I need to use any load testing tool? Or Can I simply write a PHP script to do this? Any thoughts?

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  • .NET application with an Oracle Database

    - by Pavitar
    I have to code a desktop application and some dynamic web content. I'm planning to develop it in .NET with an Oracle database, though my dilemma is that my professor says that if I do so, there would be a lot of support issues later on. He says .NET is more compatible with MS SQL and MS Access, and so is the trend, everyone does it.Is it true? I have learnt Oracle so I know of a few features which I wouldn't be able to implement on SQL comfortably because of lack of knowledge of SQL databases.I would love to learn the new syntax but again, I don't have much time to spare.

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  • SQL Database dilemma : Optimize for Querying or Writing?

    - by Harry
    I'm working on a personal project (Search engine) and have a bit of a dilemma. At the moment it is optimized for writing data to the search index and significantly slow for search queries. The DTA (Database Engine Tuning Adviser) recommends adding a couple of Indexed views inorder to speed up search queries. But this is to the detriment of writing new data to the DB. It seems I can't have one without the other! This is obviously not a new problem. What is a good strategy for this issue?

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  • CALayer not obeying object ownership rules?

    - by eaigner
    I have a custom CALayer - UIProgressLayer - for simulating a progress bar. There is a dispatched GC timer involved to animate its intermediate state. So thats the layer I'm talking about here, although i don't think the problem is restricted to this particular subclass because a CALayer with only the -release and -dealloc overridden produces the same outcome. The problem is when i send this layer, for instance, a theLayer.opacity = 0.5f a -release message is sent to the layer, thus deallocating my layer. Why is this happening? Has it something to do with how the whole CA system works? But it still has to obey the object ownership rules right? I was thinking maybe it creates a copy of that layer for the fading, but that's not the case.

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  • rais belong_to which class to choose

    - by Small Wolf
    There is a model relation like this. class A belongs_to :ref_config,:class_name => 'User' end My question is : the A has a attribute named flag, now i want to create a function like this: if flag == 1, I want the class A like this belongs_to :ref_config,:class_name => 'Department and if flag == 2, i want the class A like this belongs_to :ref_config,:class_name => 'User' How can I implement the function Thank you!

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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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