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  • Class as first-class object

    - by mrpyo
    Could a class be a first-class object? If yes, how would the implementation look? I mean, how could syntax for dynamically creating new classes look like? EDIT: I mean what example syntax could look like (I'm sorry, English is not my native language), but still I believe this question makes sense - how you give this functionality while keeping language consistent. For example how you create reference for new type. Do you make reference first-class object too and then use something like this: Reference<newType> r = new Reference<newType>(); r.set(value); Well this could get messy so you may just force user to use Object type references for dynamically created classes, but then you loose type-checking. I think creating concise syntax for this is interesting problem which solving could lead to better language design, maybe language which is metalanguage for itself (I wonder if this is possible).

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  • Are UML class diagrams adequated to design javascript systems?

    - by Vandell
    Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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  • Is OO-programming really as important as hiring companies place it?

    - by ale
    I am just finishing my masters degree (in computing) and applying for jobs.. I've noticed many companies specifically ask for an understanding of object orientation. Popular interview questions are about inheritance, polymorphism, accessors etc. Is OO really that crucial? I even had an interview for a programming job in C and half the interview was OO. In the real world, developing real applications, is object orientation nearly always used? Are key features like polymorphism used A LOT? I think my question comes from one of my weaknesses.. although I know about OO.. I don't seem to be able to incorporate it a great deal into my programs. I would be really interested to get peoples' thoughts on this!

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  • should I extend or create instance of the class

    - by meWantToLearn
    I have two classes Class A and Class B in Class A, i have three methods that perform the save, delete and select operation based upon the object I pass them. in Class B I perform the logic operations, such as modification to the property of the object before being passed to the methods of Class A, My problem is in Class B, should it extend Class A, and call the methods of class A , by parent::methodName or create instance of class A and then call Class A does not includes any property just methods. class A{ public function save($obj){ //code here } public function delete($obj){ //code here } public function select($obj){ //code here } } //Should I extend class A, and call the method by parent::methodName($obj) or create an instance of class A, call the method $instanceOfA-methodName($obj); class B extends A{ public function checkIfHasSaved($obj){ if($obj->saved == 'Yes'){ parent::save($obj); //**should I call the method like this** $instanceOFA = new A(); //**or create instance of class A and call without extending class A** instanceOFA->save($obj); } //other logic operations here } }

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  • How can a collection class instantiate many objects with one database call?

    - by Buttle Butkus
    I have a baseClass where I do not want public setters. I have a load($id) method that will retrieve the data for that object from the db. I have been using static class methods like getBy($property,$values) to return multiple class objects using a single database call. But some people say that static methods are not OOP. So now I'm trying to create a baseClassCollection that can do the same thing. But it can't, because it cannot access protected setters. I don't want everyone to be able to set the object's data. But it seems that it is an all-or-nothing proposition. I cannot give just the collection class access to the setters. I've seen a solution using debug_backtrace() but that seems inelegant. I'm moving toward just making the setters public. Are there any other solutions? Or should I even be looking for other solutions?

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  • Where is the object browser in VS 2010

    - by Keltari
    I am teaching myself C# and Im using a book that references Visual Studio 2008. However, I am using VS 2010. The book wants me to look at the object browser by choosing View, Other Windows, Object Browser from the menu. However, the object browser is not there. I moused over the icons on the menu and nothing stood out. So, where is it? Also, am I going to run into more problems like this? Is it worth getting an updated book?

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  • How to make a queue switches from FIFO mode to priority mode?

    - by enzom83
    I would like to implement a queue capable of operating both in the FIFO mode and in the priority mode. This is a message queue, and the priority is first of all based on the message type: for example, if the messages of A type have higher priority than the messages of the B type, as a consequence all messages of A type are dequeued first, and finally the messages of B type are dequeued. Priority mode: my idea consists of using multiple queues, one for each type of message; in this way, I can manage a priority based on the message type: just take first the messages from the queue at a higher priority and progressively from lower priority queues. FIFO mode: how to handle FIFO mode using multiple queues? In other words, the user does not see multiple queues, but it uses the queue as if it were a single queue, so that the messages leave the queue in the order they arrive when the priority mode is disabled. In order to achieve this second goal I have thought to use a further queue to manage the order of arrival of the types of messages: let me explain better with the following code snippet. int NUMBER_OF_MESSAGE_TYPES = 4; int CAPACITY = 50; Queue[] internalQueues = new Queue[NUMBER_OF_MESSAGE_TYPES]; Queue<int> queueIndexes = new Queue<int>(CAPACITY); void Enqueue(object message) { int index = ... // the destination queue (ie its index) is chosen according to the type of message. internalQueues[index].Enqueue(message); queueIndexes.Enqueue(index); } object Dequeue() { if (fifo_mode_enabled) { // What is the next type that has been enqueued? int index = queueIndexes.Dequeue(); return internalQueues[index].Dequeue(); } if (priority_mode_enabled) { for(int i=0; i < NUMBER_OF_MESSAGE_TYPES; i++) { int currentQueueIndex = i; if (!internalQueues[currentQueueIndex].IsEmpty()) { object result = internalQueues[currentQueueIndex].Dequeue(); // The following statement is fundamental to a subsequent switching // from priority mode to FIFO mode: the messages that have not been // dequeued (since they had lower priority) remain in the order in // which they were queued. queueIndexes.RemoveFirstOccurrence(currentQueueIndex); return result; } } } } What do you think about this idea? Are there better or more simple implementations?

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  • Use unnamed object to invoke method or not?

    - by Chen OT
    If I have a class with only only public method. When I use this class, is it good to use unnamed object to invoke its method? normal: TaxFileParser tax_parser(tax_file_name); auto content = tax_parser.get_content(); or unnamed object version: auto content = TaxFileParser(tax_file_name).get_content(); Because I've told that we should avoid temporary as possible. If tax_parser object is used only once, can I call it a temporary and try to eliminate it? Any suggestion will be helpful.

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  • Is OOP hard because it is not natural?

    - by zvrba
    One can often hear that OOP naturally corresponds to the way people think about the world. But I would strongly disagree with this statement: We (or at least I) conceptualize the world in terms of relationships between things we encounter, but the focus of OOP is designing individual classes and their hierarchies. Note that, in everyday life, relationships and actions exist mostly between objects that would have been instances of unrelated classes in OOP. Examples of such relationships are: "my screen is on top of the table"; "I (a human being) am sitting on a chair"; "a car is on the road"; "I am typing on the keyboard"; "the coffee machine boils water", "the text is shown in the terminal window." We think in terms of bivalent (sometimes trivalent, as, for example in, "I gave you flowers") verbs where the verb is the action (relation) that operates on two objects to produce some result/action. The focus is on action, and the two (or three) [grammatical] objects have equal importance. Contrast that with OOP where you first have to find one object (noun) and tell it to perform some action on another object. The way of thinking is shifted from actions/verbs operating on nouns to nouns operating on nouns -- it is as if everything is being said in passive or reflexive voice, e.g., "the text is being shown by the terminal window". Or maybe "the text draws itself on the terminal window". Not only is the focus shifted to nouns, but one of the nouns (let's call it grammatical subject) is given higher "importance" than the other (grammatical object). Thus one must decide whether one will say terminalWindow.show(someText) or someText.show(terminalWindow). But why burden people with such trivial decisions with no operational consequences when one really means show(terminalWindow, someText)? [Consequences are operationally insignificant -- in both cases the text is shown on the terminal window -- but can be very serious in the design of class hierarchies and a "wrong" choice can lead to convoluted and hard to maintain code.] I would therefore argue that the mainstream way of doing OOP (class-based, single-dispatch) is hard because it IS UNNATURAL and does not correspond to how humans think about the world. Generic methods from CLOS are closer to my way of thinking, but, alas, this is not widespread approach. Given these problems, how/why did it happen that the currently mainstream way of doing OOP became so popular? And what, if anything, can be done to dethrone it?

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  • Replaceable parameter syntax meaning

    - by Alexander N.
    Replaceable parameter syntax for the console object in C#. I am taking the O'Reilly C# Course 1 and it is asking for a replaceable parameter syntax and it is not very clear on what that means. Currently I used this: double trouble = 99999.0009; double bubble = 11111.0001; Console.WriteLine(trouble * bubble); Am I missing the meaning of replaceable parameter syntax? Can someone provide an example for what I am looking for? Original question for the quiz: "Create two variables, both doubles, assign them numbers greater than 10,000, and include a decimal component. Output the result of multiplying the numbers together, but use replaceable parameter syntax of the Console object, and multiply the numbers within the call to the Console.WriteLine() method."

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  • Are UML class diagrams adequate to design javascript systems?

    - by Vandell
    Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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  • Unity: Render 2D textures on a 3D object's face

    - by www.Sillitoy.com
    I am not familiar with 3D graphics and I'd like to know what is the right way to render some 2D figures on different points of a wider face of a 3D object. My 3D object is just a cube representing a poker table. I have 2D png for players placeholders and I'd like to render these figures on the 3D object where needed. An alternative solution would be to render the whole face with a big picture containing all the placeholders figures. However it would be a waste of memory and thus less efficient. What do you suggest me?

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  • Camera placement sphere for an always fully visible object

    - by BengtR
    Given an object: With the bounds [x, y, z, width, height, depth] And an orthographic projection [left, right, bottom, top, near, far] I want to determine the radius of a sphere which allows me to randomly place my camera on so that: The object is fully visible from all positions on this sphere The sphere radius is the smallest possible value while still satisfying 1. Assume the object is centered around the origin. How can I find this radius? I'm currently using sqrt(width^2 + height^2 + depth^2) but I'm not sure that's the correct value, as it doesn't take the camera into account. Thanks for any advice. I'm sorry for confusing a few things here. My comments below should clarify what I'm trying to do actually.

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  • APress deal of the day 13/Sep/2012 - Beginning C# Object-Oriented Programming

    - by TATWORTH
    Today's $10 deal of the day from APress at http://www.apress.com/9781430235309 is Beginning C# Object-Oriented Programming"Beginning C# Object-Oriented Programming brings you into the modern world of development, as you master the fundamentals of programming with C# and learn to develop efficient, reusable, elegant code through the object-oriented programming (OOP) methodology."  Here is a summary of my earlier review:This is a good book to learn C# by doing something practical. The book provides an excellent series of hands-on activities.So should you get a copy for your trainee C# programmers? Yes!Do I recommend it for people learning C# 2010 on their own? Yes!Those of you who have written to me for training in C# (assuming the messages were not from BOTS!), should you buy this book - YES!

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  • OO Software Architecture - base class that everything inherits from. Bad/good idea?

    - by ale
    I am reviewing a proposed OO software architecture that looks like this: Base Foo Something Bar SomethingElse Where Base is a static class. My immediate thought was that every object in any class will inherit all the methods in Base which would create a large object. Could this cause problems for a large system? The whole architecture is hierarchical.. the 'tree' is much bigger than this really. Does this sort of architecture have a name (hierarchical?!). What are the known pros and cons?

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  • Repelling a rigidbody in the direction an object is rotating

    - by ndg
    Working in Unity, I have a game object which I rotate each frame, like so: void Update() { transform.Rotate(new Vector3(0, 1, 0) * speed * Time.deltaTime); } However, I'm running into problems when it comes to applying a force to rigidbodies that collide with this game objects sphere collider. The effect I'm hoping to achieve is that objects which touch the collider are thrown in roughly the same direction as the object is rotating. To do this, I've tried the following: Vector3 force = ((transform.localRotation * Vector3.forward) * 2000) * Time.deltaTime; collision.gameObject.rigidbody.AddForce(force, ForceMode.Impulse); Unfortunately this doesn't always match the rotation of the object. To debug the issue, I wrote a simple OnDrawGizmos script, which (strangely) appears to draw the line correctly oriented to the rotation. void OnDrawGizmos() { Vector3 pos = transform.position + ((transform.localRotation * Vector3.forward) * 2); Debug.DrawLine(transform.position, pos, Color.red); } You can see the result of the OnDrawGizmos function below: What am I doing wrong?

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  • Render 2D textures on a 3D object's face

    - by www.Sillitoy.com
    I am not familiar with 3D graphics, and I'd like to know the right way to render some 2D figures on different points of a wider face of a 3D object. My 3D object is just a cube representing a poker table. I have a 2D png for players' placeholders, and I'd like to render these figures on the 3D object where needed. An alternative solution would be to render the whole face with a big picture containing all the placeholders figures. However, it would be a waste of memory and thus less efficient. What do you suggest?

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  • DDD: service contains two repository

    - by tikhop
    Does it correct way to have two repository inside one service and will it be an application or domain service? Suppose I have a Passenger object that should contains Passport (government id) object. I am getting Passenger from PassengerRepository. PassengerRepository create request to server and obtain data (json) than parse received data and store inside repository. I have confused because I want to store Passport as Entity and put it to PassportRepository but all information about password contains inside json than i received above. I guess that I should create a PassengerService that will be include PassengerRepository and PassportRepository with several methods like removePassport, addPassport, getAllPassenger and etc. UPDATE: So I guess that the better way is represent Passport as VO and store all passports inside Passenger aggregate. However there is another question: Where I should put the methods (methods calls server api) for management passenger's passport. I think the better place is so within Passenger aggregate.

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  • camera movement along with model

    - by noddy
    I am making a game in which a cube travels along a maze with the motive of crossing the maze safely. I have two problems in this. The cube needs to have a smooth movement like it is traveling on a frictionless surface. So could someone help me achieve this. I need to have this done in a event callback function I need to move the camera along with the cube. So could someone advice me a good tutorial about camera positions along with an object?

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  • Have I mistakenly assumed that my routines are loosely coupled?

    - by Tarun
    My Selenium test structures goes as - Data Object class - public class RegistrationData { String firstName = "test first name"; String lastName = "test last name"; // Getter Setter Here } Page Object class which carries out operations on a Web Page - public class RegistrationPage { private RegistrationData regData; public void setRegistrationData(RegistrationData regData) { this.regData = regData(); public NewAccountPage fillRegForm() { enterFirstName("FirstNameTextBoxLocator", regData.getFirstName); enterLastName("LastNameTextBoxLocator", regData.getLastName); // Some more fields are filled here return NewAccountPage(); } } And test class uses them as - public class TestRegistration extends SelTestCase { @Test public void testRegNewUser() { RegistrationData regData = new RegistrationData(); RegistrationPage regPage = New RegistrationPage(); regPage.setRegistrationData(regData) regPage.fillRegForm(); // Some assertion here } } Now since fillRegForm method does not take any argument, Can I assume that it is an example of loose coupling despite I need to set RegistrationData in RegistrationPage before being able to use fillRegForm method.

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  • OOP Structure for web application

    - by Query
    Ok so I have a website in which users complete tasks to earn points. When they earn enough points, they rise in rank. The site from my understanding is very basic and only executes one query or two queries at most a page. There is a user table, a support ticket table, and an orders table. All of these contain a relational row for username. Our class was familiarized with OOP back in highschool with Java but that was for video games and I could grasp the concept on why you would need a class player and class enemy. However I don't understand it's web application. At least not in my situation. I understand the user class might contain stuff like: getUsername getPoints getEmail setEmail addPoints (does this belong here? OR only things the user can manipulate should be here?) etc.. But I'm at a loss with everything else such as user registration. Can you help give me a wire framework that I could wrap my head around? Pointing me to a good eBook would help greatly

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  • In some games, we just let the main() loop be the Player object or Table object?

    - by ????
    I was thinking that let's say if there is a game of Blackjack or MasterMind, then we should have a class called Dealer or ComputerPal, which is how the computer interact with us (as a dealer for Blackjack or as the person giving hints for MasterMind). And then there should be a Player object, and the way to play one game is aPlayer.playGame but I noticed that a book was just using the main() loop to act as the player (or as the Controller of the game), calling the Dealer methods to dealer the cards, ask for player's action, etc... 1) Is this just a lazy way to model all the proper objects? 2) If more objects are to be added, who should call the aDealer.dealCards and then ask for aPlayer.askForAction? (because it is strange to let the Player handle all the logical steps). Should there be a Table object that handle all these logic and then to play one round of game, use aTable.playGame? What is a good object design for such game?

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  • Should Business Interfaces be part of the Model layer?

    - by Mik378
    In an oriented-services enterprise application, isn't it an antipattern to mix Service APIs (containing interface that external users depends on) with Model objects (entities, custom exceptions objects etc...) ? According to me, Services should only depends on Model layer but never mixed with it. In fact, my colleague told me that it doesn't make sense to separate it since client need both. (model and service interfaces) But I notice that everytime a client asks for some changes, like adding a new method in some interface (means a new service), Model layer has to be also delivered... Thus, client who has not interested by this "addition" is constrained to be concerned by this update of Model... and in a large enterprise application, this kind of delivery is known to be very risked... What is the best practice ? Separate services(only interfaces so) and model objects or mix it ?

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  • Is there a way to customize how the value for a custom Model Field is displayed in a template?

    - by Jordan Reiter
    I am storing dates as an integer field in the format YYYYMMDD, where month or day is optional. I have the following function for formatting the number: def flexibledateformat(value): import datetime, re try: value = str(int(value)) except: return None match = re.match(r'(\d{4})(\d\d)(\d\d)$',str(value)) if match: year_val, month_val, day_val = [int(v) for v in match.groups()] if day_val: return datetime.datetime.strftime(datetime.date(year_val,month_val,day_val),'%b %e, %Y') elif month_val: return datetime.datetime.strftime(datetime.date(year_val,month_val,1),'%B %Y') else: return str(year_val) Which results in the following outputs: >>> flexibledateformat(20100415) 'Apr 15, 2010' >>> flexibledateformat(20100400) 'April 2010' >>> flexibledateformat(20100000) '2010' So I'm wondering if there's a function I can add under the model field class that would automatically call flexibledateformat. So if there's a record r = DataRecord(name='foo',date=20100400) when processed in the form the value would be 20100400 but when output in a template using {{ r.date }} it shows up as "April 2010". Further clarification I do normally use datetime for storing date/time values. In this specific case, I need to record non-specific dates: "x happened in 2009", "y happened sometime in June 1996". The easiest way to do this while still preserving most of the functionality of a date field, including sorting and filtering, is by using an integer in the format of yyyymmdd. That is why I am using an IntegerField instead of a DateTimeField. This is what I would like to happen: I store what I call a "Flexible Date" in a FlexibleDateField as an integer with the format yyyymmdd. I render a form that includes a FlexibleDateField, and the value remains an integer so that functions necessary for validating it and rendering it in widgets work correctly. I call it in a template, as in {{ object.flexibledate }} and it is formatted according to the flexibledateformat rules: 20100416 - April 16, 2010; 20100400 - April 2010; 20100000 - 2010. This also applies when I'm not calling it directly, such as when it's used as a header in admin (http://example.org/admin/app_name/model_name/). I'm not aware if these specific things are possible.

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  • [Database] How to model this one-to-one relation?

    - by pbean
    I have several entities which respresent different types of users who need to be able to log in to a particular system. Additionally, they have different types of information associated with them. For example: a "general user", which has an e-mail address and "admin user", which has a workstation number (note that this a hypothetical case). Both entities also share common properties like first name, surname, address and telephone number. Finally, they naturally need to have a (unique) user name and a password to log in. In the application, the user just has to fill in his user name and password, and the functionality of the application changes slightly according to the type of the user. You can imagine that the username needs to be unique for this work. How should I model this effectively? I can't just create two tables, because then I can't force a unique constaint on the user name. I also can't put them all in just one table, because they have different types of specific information associated to them. I think I might need 3 seperate tables, one for "users" (with user name and password), one for the "general users" and another one for the "admin users", but how would the relations between these work? Or is there another solution? (By the way, the target DBMS is MySQL, so I don't think generalization is supported in the database system itself).

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