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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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  • 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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  • 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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  • 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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  • Keeping the meshes "thickness" the same when scaling an object

    - by user1806687
    I've been bashing my head for the past couple of weeks trying to find a way to help me accomplish, on first look very easy task. So, I got this one object currently made out of 5 cuboids (2 sides, 1 top, 1 bottom, 1 back), this is just for an example, later on there will be whole range of different set ups. Now, the thing is when the user chooses to scale the whole object this is what should happen: X scale: top and bottom cuboids should get scaled by a scale factor, sides should get moved so they are positioned just like they were before(in this case at both ends of top and bottom cuboids), back should get scaled so it fits like before(if I simply scale it by a scale factor it will leave gaps on each side). Y scale: sides should get scaled by a scale factor, top and bottom cuboid should get moved, and back should also get scaled. Z scale: sides, top and bottom cuboids should get scaled, back should get moved. Hope you can help, EDIT: So, I've decided to explain the situation once more, this time more detailed(hopefully). I've also made some pictures of how the scaling should look like, where is the problem and the wrong way of scaling. I this example I will be using a thick walled box, with one face missing, where each wall is made by a cuboid(but later on there will be diffrent shapes of objects, where a one of the face might be roundish, or triangle or even under some angle), scaling will be 2x on X axis. 1.This is how the default object without any scaling applied looks like: http://img856.imageshack.us/img856/4293/defaulttz.png 2.If I scale the whole object(all of the meshes) by some scale factor, the problem becomes that the "thickness" of the object walls also change(which I do not want): http://img822.imageshack.us/img822/9073/wrongwaytoscale.png 3.This is how the correct scaling should look like. Appropriate faces gets caled in this case where the scale is on X axis(top, bottom, back): http://imageshack.us/photo/my-images/163/rightwayxscale1.png/ 4.But the scale factor might not be the same for all object all of the times. In this case the back has to get scaled a bit more or it leaves gaps: http://imageshack.us/photo/my-images/9/problemwhenscaling.png/ 5.If everything goes well this is how the final object should look like: http://imageshack.us/photo/my-images/856/rightwayxscale2.png/ So, as you have might noticed there are quite a bit of things to look out when scaling. I am asking you, if any of you have any idea on how to accomplish this scaling. I have tried whole bunch of things, from scaling all of the object by the same scale factor, to subtracting and adding sizes to get the right size. But nothing I tried worked, if one mesh got scaled correctly then others didnt. Donwload the example object. English is not my first language, so I am really sorry if its hard to understand what I am saying.

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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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  • 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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  • Uncaught TypeError: Object #<an Object> has no method 'fullCalendar'

    - by Lalit
    Hi, I have embed the fullcalender control in my asp.net mvc application. It is running fine locally. but when I uploads it to my domain server (third party) it showing me This Error: Uncaught TypeError: Object # has no method 'fullCalendar' in crome console (debugger). and not rendering the control. ** EDITED: My HTML code is this ** <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" % Index <% var serializer = new System.Web.Script.Serialization.JavaScriptSerializer(); % < style type='text/css' body { margin-top: 40px; text-align: center; font-size: 14px; font-family: "Lucida Grande",Helvetica,Arial,Verdana,sans-serif; } #calendar { width: 900px; margin: 0 auto; } < script type="text/javascript" $(document).ready(function() { var date = new Date(); var d = date.getDate(); var m = date.getMonth(); var y = date.getFullYear(); var officerid = document.getElementById('officerid').value; url = "/TasksToOfficer/Calender/" + officerid; var currenteventIden = <%= serializer.Serialize( ViewData["iden"] ) %> var calendar = $('#calendar').fullCalendar({ header: { left: 'prev,next today', center: 'title', right: 'month,agendaWeek,agendaDay', border: 0 }, eventClick: function(event, element) { var title = prompt('Event Title:', event.title, { buttons: { Ok: true, Cancel: false} }); var iden = event.id; if (title) { var st = event.start; var ed = event.end; var aldy = event.allDay; var dt = event.date; event.title = title; calendar.fullCalendar('updateEvent',event); var date = new Date(st); var NextMonth = date.getMonth() + 1; var dateString = (date.getDate()) + '/' + NextMonth + '/' + date.getFullYear(); var QueryStringForEdit=null; QueryStringForEdit="officerid=" + officerid + "&description=" + title + "&date=" + dateString + "&IsForUpdate=true&iden=" + iden; if (officerid) { $.ajax( { type: "POST", url: "/TasksToOfficer/Create", data: QueryStringForEdit, success: function(result) { if (result.success) $("#feedback input").attr("value", ""); // clear all the input fields on success }, error: function(req, status, error) { } }); } } }, selectable: true, selectHelper: true, select: function(start, end, allDay) { var title = prompt('Event Title:', { buttons: { Ok: true, Cancel: false } } ); if (title) { calendar.fullCalendar('renderEvent', { title: title, start: start, end: end, allDay: allDay }, false); // This is false , because do not show same event on same date after render from server side. var date = new Date(start); var NextMonth = date.getMonth() + 1; // Reason: it is bacause of month array it starts from 0 var dateString = (date.getDate()) + '/' + NextMonth + '/' + date.getFullYear(); if (officerid) { $.ajax({ type: "POST", url: "/TasksToOfficer/Create", data: "officerid=" + officerid + "&description=" + title + "&date=" + dateString + "&IsForUpdate=false", success: function(result) { if (result.success) $("#feedback input").attr("value", ""); //$("#feedback_status").slideDown(250).text(result.message); }, error: function(req, status, error) { } }); } } calendar.fullCalendar('unselect'); }, editable: true, events: url }); }); //--------------------------------------------------------------------------// </script > <h2> Index</h2> <div id="calendar"> </div> <input id="officerid" type="hidden" value="<%=ViewData["officerid"].ToString()%>" />

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  • How to conciliate OOAD and Database Design?

    - by user1620696
    Recently I've studied about object oriented analysis and design and I liked a lot about it. In every place I've read people say that the idea is to start with the minimum set of requirements and go improving along the way, revisiting this each iteration and making it better as we contiuously develop and contact the customer interested in the software. In particular, one course from Lynda.com said a lot of that: we don't want to spend a lot of time planing everything upfront, we just want to have the minimum to get started and then improve this each iteration. Now, I've also seem a course from the same guy about database design, and there he says differently. He says that although when working with object orientation he likes the agile iterative approach, for database design we should really spend a lot of time planing things upfront instead of just going along the way with the minimum. But this confuses me a little. Indeed, the database will persist important data from our domain model and perhaps configurations of the software and so on. Now, if I'm going to continuously revist the analysis and design of the model, it seems the database design should change also. In the same way, if we plan all the database upfront it seems we are also planing all the model upfront, so the two ideas seems to be incompatible. I really like agile iterative approach, but I'm also looking at getting better design for the database also, so when working with agile iterative approach, how should we deal with the database design?

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  • IT Optimization Plan Pays Off For UK Retailer

    - by Brian Dayton
    I caught this article in ComputerworldUK yesterday. The headline talks about UK-based supermarket chain Morrisons is increasing their IT spend...OK, sounds good. Even nicer that Oracle is a big part of that. But what caught my eye were three things: 1) Morrison's truly has a long term strategy for IT. In this case, modernizing and optimizing how they use IT for business advantage.   2) Even in a tough economic climate, Morrison's views IT investments as contributing to and improving the bottom line. Specifically, "The investment in IT contributed to a 21 percent increase in Morrison's underlying profit.."   3) The phased, 3-year "Optimization Plan" took a holistic approach to their business--from CRM and Supply Chain systems to the underlying application infrastructure. On the infrastructure front, adopting a more flexible Service-Oriented Architecture enabled them to be more agile and adapt their business and Identity Management helped with sometimes mundane (but costly) issues like lost passwords and being able to document who has access to what.   Things don't always turn out so rosy. And I know it was a long and difficult process...but it's nice to see a happy ending every once in a while.  

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  • Are Get-Set methods a violation of Encapsulation?

    - by Dipan Mehta
    In an Object oriented framework, one believes there must be strict encapsulation. Hence, internal variables are not to be exposed to outside applications. But in many codebases, we see tons of get/set methods which essentially open a formal window to modify internal variables that were originally intended to be strictly prohibited. Isn't it a clear violation of encapsulation? How broadly such a practice is seen and what to do about it? EDIT: I have seen some discussions where there are two opinions in extreme: on one hand people believe that because get/set interface is used to modify any parameter, it does qualifies not be violating encapsulation. On the other hand, there are people who believe it is does violate. Here is my point. Take a case of UDP server, with methods - get_URL(), set_URL(). The URL (to listen to) property is quite a parameter that application needs to be supplied and modified. However, in the same case, if the property like get_byte_buffer_length() and set_byte_buffer_length(), clearly points to values which are quite internal. Won't it imply that it does violate the encapsulation? In fact, even get_byte_buffer_length() which otherwise doesn't modify the object, still misses the point of encapsulation, because, certainly there is an App which knows i have an internal buffer! Tomorrow, if the internal buffer is replaced by something like a *packet_list* the method goes dysfunctional. Is there a universal yes/no towards get set method? Is there any strong guideline that tell programmers (specially the junior ones) as to when does it violate encapsulation and when does it not?

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  • Web workflow solution - how should I approach the design?

    - by Tom Pickles
    We've been tasked with creating a web based workflow tool to track change management. It has a single workflow with multiple synchronous tasks for the most part, but branch out at a point to tasks running in parallel which meet up later on. There will be all sorts of people using the application, and all of them will need to see their outstanding tasks for each change, but only theirs, not others. There will also be a high level group of people who oversee all changes, so need to see everything. They will need to see tasks which have not been done in the specified time, who's responsible etc. The data will be persisted to a SQL database. It'll all be put together using .Net. I've been trying to learn and implement OOP into my designs of late, but I'm wondering if this is moot in this instance as it may be better to have the business logic for this in stored procedures in the DB. I could use POCO's, a front end layer and a data access layer for the web application and just use it as a mechanism for CRUD actions on the DB, then use SP's fired in the DB to apply the business rules. On the other hand, I could use an object oriented design within the web app, but as the data in the app is state-less, is this a bad idea? I could try and model out the whole application into a class structure, implementing interfaces, base classes and all that good stuff. So I would create a change class, which contained a list of task classes/types, which defined each task, and implement an ITask interface etc. Put end-user types into the tasks to identify who should be doing what task. Then apply all the business logic in the respective class methods etc. What approach do you guys think I should be using for this solution?

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  • When too much encapsulation was reached

    - by Samuel
    Recently, I read a lot of gook articles about how to do a good encapsulation. And when I say "good encapsulation", I don't talk about hiding private fields with public properties; I talk about preventing users of your Api to do wrong things. Here is two good articles about this subject: http://blog.ploeh.dk/2011/05/24/PokayokeDesignFromSmellToFragrance.aspx http://lostechies.com/derickbailey/2011/03/28/encapsulation-youre-doing-it-wrong/ At my job, the majority a our applications are not destined to other programmers but rather to the customers. About 80% of the application code is at the top of the structure (Not used by other code). For this reason, there is probably no chance ever that this code will be used by other application. An example of encapsulation that prevent user to do wrong thing with your Api is to return an IEnumerable instead of IList when you don't want to give the ability to the user to add or remove items in the list. My question is: When encapsulation could be considered like too much of purism object oriented programming while keeping in mind that each hour of programming is charged to the customer? I want to do good code that is maintainable, easy to read and to use but when this is not a public Api (Used by other programmer), where could we put the line between perfect code and not so perfect code? Thank you.

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  • Is comparing an OO compiler to a SQL compiler/optimizer valid?

    - by Brad
    I'm now doing a lot of SQL development at my new job where as before I was doing Object Oriented desktop app stuff. I keep running across very large scripts (thousands of lines) and wanting to refactor in some way. I am seeing that SQL is a different sort of beast and it's probably fine to have these big scripts for the most part but while explaining this to me people are also insisting that the whole idea of refactoring is bad. That stuff like the .NET compiler are actually burdened by refactored code and that a big wall of code is more efficient and better design than code designed for reuse, readability and scalability. The other argument is that OO compilers are almost dangerously inefficient and don't have efficient memory management or runs too many CPU instructions compared to older "simpler" compilers and compared to SQL. Are these valid complaints? Even if some compiler like a C compiler is modestly more "efficient" (whatever that means on this high of a level without seeing code) would you want to write applications in C over C# or Java? Is comparing an OO compiler to a SQL compiler/optimizer even valid?

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  • Getting rid of Massive View Controller in iOS?

    - by Earl Grey
    I had a discussion with my colleague about the following problem. We have an application where we need filtering functionality. On any main screen within the upper navigation bar, there is a button in the upper right corner. Once you touch that button, an custom written Alert View like view will pop up modally, behind it a semitransparent black overlay view. In that modal view, there is a table view of options, and you can choose one exclusively. Based on your selection, once this modal view is closed, the list of items in the main view is filtered. It is simply a modally presented filter to filter the main table view.This UI design is dictated by the design department, I cannot do anything about it so let accept this as a premise. Also the main filter button in the navbar will change colours to indicate that the filter is active. The question I have is about implementation. I suggested to my colleague that we create a separate XYZFilter class that will be an instance created by the main view controller acquire the filtering options handle saving and restoration of its state - i.e. last filter selected provide its two views - the overlay view and the modal view be the datasource for the table in its modal view. For some unknown reason, my colleague was not impressed by that approach at all. He simply wants to do these functionalities in the main view controller, maybe out of being used to do this in the past like that :-/ Is there any fundamental problem with my approach? I want to keep the view controller small, not to have spaghetti code create a reusable component (for use outside the project) have more object oriented, decoupled approach. prevent duplication of code as we need the filtering in two different places but it looks the same in both.. Any advice?

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  • IT Optimization Plan Pays Off For UK Retailer

    - by [email protected]
    I caught this article in ComputerworldUK yesterday. The headline talks about UK-based supermarket chain Morrisons is increasing their IT spend...OK, sounds good. Even nicer that Oracle is a big part of that. But what caught my eye were three things: 1) Morrison's truly has a long term strategy for IT. In this case, modernizing and optimizing how they use IT for business advantage. 2) Even in a tough economic climate, Morrison's views IT investments as contributing to and improving the bottom line. Specifically, "The investment in IT contributed to a 21 percent increase in Morrison's underlying profit.." 3) The phased, 3-year "Optimization Plan" took a holistic approach to their business--from CRM and Supply Chain systems to the underlying application infrastructure. On the infrastructure front, adopting a more flexible Service-Oriented Architecture enabled them to be more agile and adapt their business and Identity Management helped with sometimes mundane (but costly) issues like lost passwords and being able to document who has access to what. Things don't always turn out so rosy. And I know it was a long and difficult process...but it's nice to see a happy ending every once in a while.

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  • What is the ideal length of a method?

    - by iPhoneDeveloper
    In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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  • Teaching OO to VBA developers [closed]

    - by Eugene
    I work with several developers that come from less object oriented background like (VB6, VBA) and are mostly self-taught. As part of moving away from those technologies we recently we started having weekly workshops to go over the features of C#.NET and OO practices and design principles. After a couple of weeks of basic introduction I noticed that they had a lot of problems implementing even basic code. For instance it took probably 15 minutes to implement a Stack.push() and a full hour to implement a simple Stack fully. These developers were trying to do things like passing top index as a parameter to the method, not creating an private array, using variables out of scope. But most of all not going through the "design (dia/mono)log" (I need something to do X, so maybe I'll make an array, or put it here). I am a little confused because they are smart people and are able to produce functional code in their traditional environments. I'm curious if anybody else has encountered a similar thing and if there are any particular resources, exercises, books, ideas that would be helpful in this circumstance.

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  • Data classes: getters and setters or different method design

    - by Frog
    I've been trying to design an interface for a data class I'm writing. This class stores styles for characters, for example whether the character is bold, italic or underlined. But also the font-size and the font-family. So it has different types of member variables. The easiest way to implement this would be to add getters and setters for every member variable, but this just feels wrong to me. It feels way more logical (and more OOP) to call style.format(BOLD, true) instead of style.setBold(true). So to use logical methods insteads of getters/setters. But I am facing two problems while implementing these methods: I would need a big switch statement with all member variables, since you can't access a variable by the contents of a string in C++. Moreover, you can't overload by return type, which means you can't write one getter like style.getFormatting(BOLD) (I know there are some tricks to do this, but these don't allow for parameters, which I would obviously need). However, if I would implement getters and setters, there are also issues. I would have to duplicate quite some code because styles can also have a parent styles, which means the getters have to look not only at the member variables of this style, but also at the variables of the parent styles. Because I wasn't able to figure out how to do this, I decided to ask a question a couple of weeks ago. See Object Oriented Programming: getters/setters or logical names. But in that question I didn't stress it would be just a data object and that I'm not making a text rendering engine, which was the reason one of the people that answered suggested I ask another question while making that clear (because his solution, the decorator pattern, isn't suitable for my problem). So please note that I'm not creating my own text rendering engine, I just use these classes to store data. Because I still haven't been able to find a solution to this problem I'd like to ask this question again: how would you design a styles class like this? And why would you do that? Thanks on forehand!

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  • Mocking concrete class - Not recommended

    - by Mik378
    I've just read an excerpt of "Growing Object-Oriented Software" book which explains some reasons why mocking concrete class is not recommended. Here some sample code of a unit-test for the MusicCentre class: public class MusicCentreTest { @Test public void startsCdPlayerAtTimeRequested() { final MutableTime scheduledTime = new MutableTime(); CdPlayer player = new CdPlayer() { @Override public void scheduleToStartAt(Time startTime) { scheduledTime.set(startTime); } } MusicCentre centre = new MusicCentre(player); centre.startMediaAt(LATER); assertEquals(LATER, scheduledTime.get()); } } And his first explanation: The problem with this approach is that it leaves the relationship between the objects implicit. I hope we've made clear by now that the intention of Test-Driven Development with Mock Objects is to discover relationships between objects. If I subclass, there's nothing in the domain code to make such a relationship visible, just methods on an object. This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I can't figure out exactly what he means when he says: This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I understand that the service corresponds to MusicCentre's method called startMediaAt. What does he mean by "elsewhere"? The complete excerpt is here: http://www.mockobjects.com/2007/04/test-smell-mocking-concrete-classes.html

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  • My proposed design is usually worse than my colleague's - how do I get better?

    - by user151193
    I have been programming for couple of years and am generally good when it comes to fixing problems and creating small-to-medium scripts, however, I'm generally not good at designing large scale programs in object oriented way. Few questions Recently, a colleague who has same number of years of experience as me and I were working on a problem. I was working on a problem longer than him, however, he came up with a better solution and in the end we're going to use his design. This really affected me. I admit his design is better, but I wanted to come up with a design as good as his. I'm even contemplating quitting the job. Not sure why but suddenly I feel under some pressure e.g. what would juniors think of me and etc? Is it normal? Or I'm thinking a little too much into this? My job involves programming in Python. I try to read source code but how do you think I can improve me design skills? Are there any good books or software that I should study? Please enlighten me. I will really appreciate your help.

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  • Python Glade could not create GladeXML Object

    - by Peter
    Hey, I've created a simple window GUI in Glade 3.6.7 and I am trying to import it into Python. Every time I try to do so I get the following error: (queryrelevanceevaluation.py:8804): libglade-WARNING **: Expected <glade-interface>. Got <interface>. (queryrelevanceevaluation.py:8804): libglade-WARNING **: did not finish in PARSER_FINISH state Traceback (most recent call last): File "queryrelevanceevaluation.py", line 17, in <module> app = QueryRelevanceEvaluationApp() File "queryrelevanceevaluation.py", line 10, in __init__ self.widgets = gtk.glade.XML(gladefile) RuntimeError: could not create GladeXML object My Python Code: #!/usr/bin/env python import gtk import gtk.glade class QueryRelevanceEvaluationApp: def __init__(self): gladefile = "foo.glade" self.widgets = gtk.glade.XML(gladefile) dic = {"on_buttonGenerate_clicked" : self.on_buttonGenerate_clicked} self.widgets.signal_autoconnect(dic) def on_buttonGenerate_clicked(self, widget): print "You clicked the button" app = QueryRelevanceEvaluationApp() gtk.main() And the foo.glade file: <?xml version="1.0"?> <interface> <requires lib="gtk+" version="2.16"/> <!-- interface-naming-policy project-wide --> <object class="GtkWindow" id="windowRelevanceEvaluation"> <property name="visible">True</property> <property name="title" translatable="yes">Query Result Relevance Evaluation</property> <child> <object class="GtkVBox" id="vbox1"> <property name="visible">True</property> <property name="orientation">vertical</property> <child> <object class="GtkHBox" id="hbox2"> <property name="visible">True</property> <child> <object class="GtkLabel" id="labelQuery"> <property name="visible">True</property> <property name="label" translatable="yes">Query:</property> </object> <packing> <property name="expand">False</property> <property name="padding">4</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkEntry" id="entry1"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="invisible_char">&#x25CF;</property> </object> <packing> <property name="padding">4</property> <property name="position">1</property> </packing> </child> </object> <packing> <property name="position">0</property> </packing> </child> <child> <object class="GtkFrame" id="frameSource"> <property name="visible">True</property> <property name="label_xalign">0</property> <child> <object class="GtkAlignment" id="alignment1"> <property name="visible">True</property> <property name="left_padding">12</property> <child> <object class="GtkHButtonBox" id="hbuttonbox1"> <property name="visible">True</property> <child> <object class="GtkRadioButton" id="radiobuttonGoogle"> <property name="label" translatable="yes">Google</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonBing"> <property name="label" translatable="yes">Bing</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">1</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonBoden"> <property name="label" translatable="yes">Boden</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">2</property> </packing> </child> <child> <object class="GtkRadioButton" id="radiobuttonCSV"> <property name="label" translatable="yes">CSV</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">False</property> <property name="active">True</property> <property name="draw_indicator">True</property> </object> <packing> <property name="expand">False</property> <property name="fill">False</property> <property name="position">3</property> </packing> </child> </object> </child> </object> </child> <child type="label"> <object class="GtkLabel" id="labelFrameSource"> <property name="visible">True</property> <property name="label" translatable="yes">&lt;b&gt;Source&lt;/b&gt;</property> <property name="use_markup">True</property> </object> </child> </object> <packing> <property name="position">1</property> </packing> </child> <child> <object class="GtkFrame" id="frame1"> <property name="visible">True</property> <property name="label_xalign">0</property> <child> <object class="GtkHBox" id="hbox3"> <property name="visible">True</property> <child> <object class="GtkLabel" id="labelResults"> <property name="visible">True</property> <property name="label" translatable="yes">Number Results:</property> </object> <packing> <property name="expand">False</property> <property name="position">0</property> </packing> </child> <child> <object class="GtkSpinButton" id="spinbuttonResults"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="invisible_char">&#x25CF;</property> </object> <packing> <property name="padding">4</property> <property name="position">1</property> </packing> </child> </object> </child> <child type="label"> <object class="GtkLabel" id="labelFrameResults"> <property name="visible">True</property> <property name="label" translatable="yes">&lt;b&gt;Results&lt;/b&gt;</property> <property name="use_markup">True</property> </object> </child> </object> <packing> <property name="padding">2</property> <property name="position">2</property> </packing> </child> <child> <object class="GtkButton" id="buttonGenerateResults"> <property name="label" translatable="yes">Generate!</property> <property name="visible">True</property> <property name="can_focus">True</property> <property name="receives_default">True</property> </object> <packing> <property name="position">3</property> </packing> </child> </object> </child> </object> </interface> foo.glade and the above python script are in the same directory, and I have tried using a fully-qualified path but still get the same error (I am certain that the path is correct!). Any ideas? Cheers, Pete

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  • Strategies for invoking subclass methods on generic objects

    - by Brad Patton
    I've run into this issue in a number of places and have solved it a bunch of different ways but looking for other solutions or opinions on how to address. The scenario is when you have a collection of objects all based off of the same superclass but you want to perform certain actions based only on instances of some of the subclasses. One contrived example of this might be an HTML document made up of elements. You could have a superclass named HTMLELement and subclasses of Headings, Paragraphs, Images, Comments, etc. To invoke a common action across all of the objects you declare a virtual method in the superclass and specific implementations in all of the subclasses. So to render the document you could loop all of the different objects in the document and call a common Render() method on each instance. It's the case where again using the same generic objects in the collection I want to perform different actions for instances of specific subclass (or set of subclasses). For example (an remember this is just an example) when iterating over the collection, elements with external links need to be downloaded (e.g. JS, CSS, images) and some might require additional parsing (JS, CSS). What's the best way to handle those special cases. Some of the strategies I've used or seen used include: Virtual methods in the base class. So in the base class you have a virtual LoadExternalContent() method that does nothing and then override it in the specific subclasses that need to implement it. The benefit being that in the calling code there is no object testing you send the same message to each object and let most of them ignore it. Two downsides that I can think of. First it can make the base class very cluttered with methods that have nothing to do with most of the hierarchy. Second it assumes all of the work can be done in the called method and doesn't handle the case where there might be additional context specific actions in the calling code (i.e. you want to do something in the UI and not the model). Have methods on the class to uniquely identify the objects. This could include methods like ClassName() which return a string with the class name or other return values like enums or booleans (IsImage()). The benefit is that the calling code can use if or switch statements to filter objects to perform class specific actions. The downside is that for every new class you need to implement these methods and can look cluttered. Also performance could be less than some of the other options. Use language features to identify objects. This includes reflection and language operators to identify the objects. For example in C# there is the is operator that returns true if the instance matches the specified class. The benefit is no additional code to implement in your object hierarchy. The only downside seems to be the lack of using something like a switch statement and the fact that your calling code is a little more cluttered. Are there other strategies I am missing? Thoughts on best approaches?

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