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• A better alternative to incompatible implementations for the same interface?

  - by glenatron

  I am working on a piece of code which performs a set task in several parallel environments where the behaviour of the different components in the task are similar but quite different. This means that my implementations are quite different but they are all based on the relationships between the same interfaces, something like this: IDataReader -> ContinuousDataReader -> ChunkedDataReader IDataProcessor -> ContinuousDataProcessor -> ChunkedDataProcessor IDataWriter -> ContinuousDataWriter -> ChunkedDataWriter So that in either environment we have an IDataReader, IDataProcessor and IDataWriter and then we can use Dependency Injection to ensure that we have the correct one of each for the current environment, so if we are working with data in chunks we use the ChunkedDataReader, ChunkedDataProcessor and ChunkedDataWriter and if we have continuous data we have the continuous versions. However the behaviour of these classes is quite different internally and one could certainly not go from a ContinuousDataReader to the ChunkedDataReader even though they are both IDataProcessors. This feels to me as though it is incorrect ( possibly an LSP violation? ) and certainly not a theoretically correct way of working. It is almost as though the "real" interface here is the combination of all three classes. Unfortunately in the project I am working on with the deadlines we are working to, we're pretty much stuck with this design, but if we had a little more elbow room, what would be a better design approach in this kind of scenario?

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• How would you model an objects representing different phases of an entity life cycle?

  - by Ophir Yoktan

  I believe the scenario is common mostly in business workflows - for example: loan management the process starts with a loan application, then there's the loan offer, the 'live' loan, and maybe also finished loans. all these objects are related, and share many fields all these objects have also many fields that are unique for each entity the variety of objects maybe large, and the transformation between the may not be linear (for example: a single loan application may end up as several loans of different types) How would you model this? some options: an entity for each type, each containing the relevant fields (possibly grouping related fields as sub entities) - leads to duplication of data. an entity for each object, but instead of duplicating data, each object has a reference to it's predecessor (the loan doesn't contain the loaner details, but a reference to the loan application) - this causes coupling between the object structure, and the way it was created. if we change the loan application, it shouldn't effect the structure of the loan entity. one large entity, with fields for the whole life cycle - this can create 'mega objects' with many fields. it also doesn't work well when there's a one to many or many to many relation between the phases.

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• A few questions about how JavaScript works

  - by KayoticSully

  I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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• Getting the ID of an object when the object is given

  - by Pieter

  I have link that calls a function when clicked: <a href="javascript:spawnMenu(this);" id="link1">Test1</a> To make my function work, I need access to the object so that I can perform jQuery operations like this: alert($(objCaller).offset().left); Since objCaller points to the object and not the object ID, this won't work. I need something like this: alert($("a#link1").offset().left); How can I get the object ID from objCaller?

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• C# Design How to Elegantly wrap a DAL class

  - by guazz

  I have an application which uses MyGeneration's dOODads ORM to generate it's Data Access Layer. dOODad works by generating a persistance class for each table in the database. It works like so: // Load and Save Employees emps = new Employees(); if(emps.LoadByPrimaryKey(42)) { emps.LastName = "Just Got Married"; emps.Save(); } // Add a new record Employees emps = new Employees(); emps.AddNew(); emps.FirstName = "Mr."; emps.LastName = "dOOdad"; emps.Save(); // After save the identity column is already here for me. int i = emps.EmployeeID; // Dynamic Query - All Employees with 'A' in thier last name Employees emps = new Employees(); emps.Where.LastName.Value = "%A%"; emps.Where.LastName.Operator = WhereParameter.Operand.Like; emps.Query.Load(); For the above example(i.e. Employees DAL object) I would like to know what is the best method/technique to abstract some of the implementation details on my classes. I don't believe that an Employee class should have Employees(the DAL) specifics in its methods - or perhaps this is acceptable? Is it possible to implement some form of repository pattern? Bear in mind that this is a high volume, perfomacne critical application. Thanks, j

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• Progressbar patterns (Eclipse)

  - by JesperE

  I've struggled quite a bit with Eclipse and progress-monitors to try to have good progressbars which report useful progress information to the user. Inevitably the code gets cluttered with lots of things like if (monitor.isCancelled()) return; ... lengthyMethodCall(monitor.newChild(10)); and all over the place I need to pass a IProgressMonitor as an argument to my methods. This is bad, for several reasons: The code gets cluttered with lots of code which is not relevant to what the function actually does. I need to manually guesstimate which parts of the code takes time, and which parts do not. It interacts badly with automated tests; where much of the information which goes into a progressbar instead should be logged for later inspection. Is there a way out of this? Are there tools which can help me out with one or more of these problems? Should I be looking at Aspect-Oriented Programming tools, or are there other alternatives?

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• Is OOP becoming easier or harder?

  - by tunmise fasipe

  When the concepts of Object Oriented Programming were introduced to programmers years back it looks interesting and programming was cleaner. OOP was like this Stock stock = new Stock(); stock.addItem(item); stock.removeItem(item); That was easier to understand with self-descriptive name. But now OOP, with pattern like Data Transfer Objects (or Value Objects), Repository, Dependency Injection etc, has become more complex. To achieve the above you may have to create several classes (e.g. abstract, factory, DAO etc) and Implement several interfaces Note: I am not against best practices that makes Collaboration, Testing and Integration easier

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• Class instance clustering in object reference graph for multi-entries serialization

  - by Juh_

  My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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• Game Design Schools in Canada

  - by CptJackLoder

  I am a High School student in Ontario and i am trying looking for college/university programs the are specifically about game design. There are quite a few at most colleges near me, but they are all BA's and I am looking for a BSc. The only one i have been able to find is at digipen but that is across the continent and more importantly outrageously expensive. Does anyone know of and programs in Canada or the US that offer a BSc in Game design?

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• The importance of Design Patterns with Javascript, NodeJs et al

  - by Lewis

  With Javascript appearing to be the ubiquitous programming language of the web over the next few years, new frameworks popping up every five minutes and event driven programming taking a lead both server and client side: Do you as a Javascript developer consider the traditional Design Patterns as important or less important than they have been with other languages / environments?. Please name the top three design patterns you, as a Javascript developer use regularly and give an example of how they have helped in your Javascript development.

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• Design Issues With Forms

  - by ultan o'broin

  Interesting article on UX Matters, well worth reading, especially the idea that global design research can take for a better user experience in all languages: Label Placement in Austrian Forms, with Some Lessons for English Forms What is perhaps underplayed here is the cultural influence of how people worked with forms in the past, and how a proper global user-centered design process needs to address this issue and move usability gains (in the enterprise space, productivity especially) in the right direction.

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• I'm interested in checking out a stack-oriented programming language. Which one would you recommend?

  - by Anto

  I'm interested in learning a stack-oriented programming language (such as Forth), which one would you recommend? The qualities I want are: You should be able to develop non-trivial software in it, but it mustn't be a great language for that as: I want to learn the language so I can try out a new paradigm (that is, not because I (think) that I will have great use of it). The reason I want to learn another paradigm is that I want to broaden my views on different approaches (learn to think in new ways, different from OOP, functional and structured). The language should let me do that (learn to think differently). The language should have available and good resources to learn from. The resources should also approach stack-oriented programming in a way that you understand the paradigm (after all, I do this for the paradigm).

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• So what *did* Alan Kay really mean by the term "object-oriented"?

  - by Charlie Flowers

  Reportedly, Alan Kay is the inventor of the term "object oriented". And he is often quoted as having said that what we call OO today is not what he meant. For example, I just found this on Google: I made up the term 'object-oriented', and I can tell you I didn't have C++ in mind -- Alan Kay, OOPSLA '97 I vaguely remember hearing something pretty insightful about what he did mean. Something along the lines of "message passing". Do you know what he meant? Can you fill in more details of what he meant and how it differs from today's common OO? Please share some references if you have any. Thanks.

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• SQL Saturday Birmingham #328 Database Design Precon In One Week

  - by drsql

  On September 22, I will be doing my "How to Design a Relational Database" pre-conference session in Birmingham, Alabama. You can see the abstract here if you are interested, and you can sign up there too, naturally. At just $100, which includes a free ebook copy of my database design book, it is a great bargain and I totally promise it will be a little over 7 hours of talking about and designing databases, which will certainly be better than what you do on a normal work day, even a Friday....(read more)

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• Development: SDK for Social Net

  - by loldop

  I have a task: development sdk for social networking service like facebook, twitter and etc. At now i'm developing facebook-extension-sdk which based on facebook-ios-sdk 3.0. But not all social networking services have good sdks. And all time i improved my facebook-extension-sdk, when i see ugly code :( Please, advise me good techniques to development these sdks (like design-patterns or your own experience or good books/sites). Thanks!

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• What do you think was a poor design choice in Java

  - by Phobia

  Java has been one of the most (the most?) popular programming languages till this day, but this also brought controversy as well. A lot of people now like to bash Java simply because "it's slow", or simply because it's not language X, for example. My question isn't related to any of these arguments at all, I simply want to know what you consider a design flaw, or a poor design choice in Java, and how it might be improved from your point of view. Something like this.

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• Book Review: SSIS Design Patterns

  - by andyleonard

  Samuel Vanga ( Blog | @SamuelVanga ) has posted a review of our new book SSIS Design Patterns at his blog . Several of Sam’s statements struck me, but none more than this: Within a few hours of reading SQL Server 2012 Integration Services Design Patterns , it stood out that none of the authors were trying to impress by showing what they all know in SSIS. Instead, they focused on describing solutions and patterns in a great detail (exactly why I paid for). Sam mentions he could not locate the source...(read more)

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• Design Patterns - Why the need for interfaces?

  - by Kyle Johnson

  OK. I am learning design patterns. Every time I see someone code an example of a design pattern they use interfaces. Here is an example: http://visualstudiomagazine.com/Articles/2013/06/18/the-facade-pattern-in-net.aspx?Page=1 Can someone explain to me why was the interfaces needed in this example to demonstrate the facade pattern? The program work if you pass in the classes to the facade instead of the interface. If I don't have interfaces does that mean

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• Design for an interface implementation that provides additional functionality

  - by Limbo Exile

  There is a design problem that I came upon while implementing an interface: Let's say there is a Device interface that promises to provide functionalities PerformA() and GetB(). This interface will be implemented for multiple models of a device. What happens if one model has an additional functionality CheckC() which doesn't have equivalents in other implementations? I came up with different solutions, none of which seems to comply with interface design guidelines: To add CheckC() method to the interface and leave one of its implementations empty: interface ISomeDevice { void PerformA(); int GetB(); bool CheckC(); } class DeviceModel1 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { bool res; // assign res a value based on some validation return res; } } class DeviceModel2 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { return true; // without checking anything } } This solution seems incorrect as a class implements an interface without truly implementing all the demanded methods. To leave out CheckC() method from the interface and to use explicit cast in order to call it: interface ISomeDevice { void PerformA(); int GetB(); } class DeviceModel1 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { bool res; // assign res a value based on some validation return res; } } class DeviceModel2 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } } class DeviceManager { private ISomeDevice myDevice; public void ManageDevice(bool newDeviceModel) { myDevice = (newDeviceModel) ? new DeviceModel1() : new DeviceModel2(); myDevice.PerformA(); int b = myDevice.GetB(); if (newDeviceModel) { DeviceModel1 newDevice = myDevice as DeviceModel1; bool c = newDevice.CheckC(); } } } This solution seems to make the interface inconsistent. For the device that supports CheckC(): to add the logic of CheckC() into the logic of another method that is present in the interface. This solution is not always possible. So, what is the correct design to be used in such cases? Maybe creating an interface should be abandoned altogether in favor of another design?

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• How did you get good practices for your OOP designs?

  - by Darf Zon

  I realized I have a difficulty creating OOP designs. I spent many time deciding if this property is correctly set it to X class. For example, this is a post which has a few days: http://codereview.stackexchange.com/questions/8041/how-to-improve-my-factory-design I'm not convinced of my code. So I want to improve my designs, take less time creating it. How did you learn creating good designs? Some books that you can recommend me?

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• Should I use JavaFx properties?

  - by Mike G

  I'm usually very careful to keep my Model, View, and Controller code separate. The thing is JavaFx properties are so convenient to bind them all together. The issue is that it makes my entire code design dependent on JavaFx, which I feel I should not being doing. I should be able to change the view without changing too much of the model and controller. So should I ignore the convenience of JavaFx properties, or should I embrace them and the fact that it reduces my codes flexibility.

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• Rule of thumb for enemy design

  - by Terrance

  I'm at the early stages of developing a 2d side scrolling open ended platformer (think metroidvania) and am having a bit of difficulty at enemy design inspiration for something of a scifi, nature, fantasy setting that isn't overly familar or obvious. I haven't seen too many articles blogs or books that talk about the subject at great length. Is there a fair rule of thumb when coming up with enemy design with respect to keeping your player engaged?

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• Can an object oriented program be seen as a Finite State Machine?

  - by Peretz

  This might be a philosophical/fundamental question, but I just want to clarify it. In my understanding a Finite State Machine is a way of modeling a system in which the system's output will not only depend on the current inputs, but also the current state of the system. Additionally, as the name suggests it, a finite state machine can be segmented in a finite N number of states with its respective state and behavior. If this is correct, shouldn't every single object with data and function members be a state in our object oriented model, making any object oriented design a finite state machine? If that is not the interpretation of a FSM in object design, what exactly people mean when they implement a FSM in software? am I missing something? Thanks

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• As a tooling/automation developer, can I be making better use of OOP?

  - by Tom Pickles

  My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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• Design Pattern for Data Validation

  - by melodui

  What would be the best design pattern for this problem: I have an Object A. Object A can either be registered or deleted from the database depending on the user request. Data validation is performed before registration or deletion of the object. There are a set of rules to be checked before the object can be registered and another set of rules for deletion. Some of these rules are common for both operations. So far, I think the Chain of Responsibility design pattern fits the most but I'm having trouble implementing it.

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