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• Cohesion and Decoupling.

  - by dbtek

  Can anyone tell me what are Cohesion and Decoupling? I found coupling but there is no Decoupling anywhere. I need to learn their meanings. Any help will be appreciated. Thanks for replying.

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• Help decoupling Crystal Report from CrystalReportViewer

  - by John at CashCommons

  I'm using Visual Studio 2005 with VB.NET. I have a number of Crystal Reports, each with their own associated dialog resource containing a CrystalReportViewer. The class definitions look like this: Imports System.Windows.Forms Imports CrystalDecisions.CrystalReports.Engine Imports CrystalDecisions.Shared Public Class dlgForMyReport Private theReport As New myCrystalReport Public theItems As New List(Of MyItem) Private Sub OK_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK_Button.Click Me.DialogResult = System.Windows.Forms.DialogResult.OK Me.Close() End Sub Private Sub Cancel_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Cancel_Button.Click Me.DialogResult = System.Windows.Forms.DialogResult.Cancel Me.Close() End Sub Private Sub dlgForMyReport_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load theReport.SetDataSource(theItems) 'Do a bunch of stuff here to set data items in theReport Me.myCrystalReportViewer.ReportSource = theReport End Sub End Class I basically instantiate the dialog, set theItems to the list I want, and call ShowDialog. I now have a need to combine several of these reports into one report (possibly like this) but the code that loads up the fields in the report is in the dialog. How would I go about decoupling the report initialization from the dialog? Thanks!

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• Dependency Injection and decoupling of software layers

  - by cs31415

  I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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• Decoupling software components via naming convention

  - by csteinmueller

  I'm currently evaluating alternatives to refactor a drivermanagement. In my multitier architecture I have Baseclass DAL.Device //my entity Interfaces BL.IDriver //handles the dataprocessing between application and device BL.IDriverCreator //creates an IDriver from a Device BL.IDriverFactory //handles the driver creation requests Every specialization of Device has a corresponding IDriver implementation and a corresponding IDriverCreator implementation. At the moment the mapping is fix via a type check within the business layer / DriverFactory. That means every new driver needs a) changing code within the DriverFactory and b) referencing the new IDriver implementation / assembly. On a customers point of view that means, every new driver, used or not, needs a complex revalidation of their hardware environment, because it's a critical process. My first inspiration was to use a caliburn micro like nameconvention see Caliburn.Micro: Xaml Made Easy BL.RestDriver BL.RestDriverCreator DAL.RestDevice After receiving the RestDevicewithin the IDriverFactory I can load all driver dlls via reflection and do a namesplitting/comparing (extracting the xx from xxDriverCreator and xxDevice) Another idea would be a custom attribute (which also leads to comparing strings). My question: is that a good approach above layer borders? If not, what would be a good approach?

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• Achieving decoupling in Model classes

  - by Guven

  I am trying to test-drive (or at least write unit tests) my Model classes but I noticed that my classes end up being too coupled. Since I can't break this coupling, writing unit tests is becoming harder and harder. To be more specific: Model Classes: These are the classes that hold the data in my application. They resemble pretty much the POJO (plain old Java objects), but they also have some methods. The application is not too big so I have around 15 model classes. Coupling: Just to give an example, think of a simple case of Order Header - Order Item. The header knows the item and the item knows the header (needs some information from the header for performing certain operations). Then, let's say there is the relationship between Order Item - Item Report. The item report needs the item as well. At this point, imagine writing tests for Item Report; you need have a Order Header to carry out the tests. This is a simple case with 3 classes; things get more complicated with more classes. I can come up with decoupled classes when I design algorithms, persistence layers, UI interactions, etc... but with model classes, I can't think of a way to separate them. They currently sit as one big chunk of classes that depend on each other. Here are some workarounds that I can think of: Data Generators: I have a package that generates sample data for my model classes. For example, the OrderHeaderGenerator class creates OrderHeaders with some basic data in it. I use the OrderHeaderGenerator from my ItemReport unit-tests so that I get an instance to OrderHeader class. The problem is these generators get complicated pretty fast and then I also need to test these generators; defeating the purpose a little bit. Interfaces instead of dependencies: I can come up with interfaces to get rid of the hard dependencies. For example, the OrderItem class would depend on the IOrderHeader interface. So, in my unit tests, I can easily mock the behaviour of an OrderHeader with a FakeOrderHeader class that implements the IOrderHeader interface. The problem with this approach is the complexity that the Model classes would end up having. Would you have other ideas on how to break this coupling in the model classes? Or, how to make it easier to unit-test the model classes?

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• Can decoupling hurt maintainability in certain situations?

  - by Ceiling Gecko

  Can the fact that the business logic is mapped to interfaces instead of implementations actually hinder the maintenance of the application in certain situations? A naive example with the Java's Hibernate framework would be, that for example (provided I don't have the whole code-base in my head, the project structure is a mess and classes are named with arbitrary names) if I wish to see what's going on in a certain DAO, to see if it actually is doing what it's supposed to do, then instead of traversing backwards up the tree from the point where the data service is invoked (where the tree will end in an interface with no implementation details whatsoever apart from the signature) I have to for example go and look for a configuration XML file to see which class is mapped to said interface as the implementation before being able to access the actual implementation details. Are there any situations where having loose coupling can actually hurt maintainability?

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• problem in decoupling urls.py , while following a tutorial of django

  - by Nitin Garg

  http://docs.djangoproject.com/en/dev/intro/tutorial03/ I was at the step Decoupling the URLconfs where the tutorial illustrates how to decouple urls.py. On doing exactly what it says, i get the following error- error at /polls/1/ nothing to repeat Request Method: GET Request URL: http://localhost:8000/polls/1/ Exception Type: error Exception Value: nothing to repeat Exception Location: C:\jython2.5.1\Lib\re.py in _compile, line 241 Python Executable: C:\jython2.5.1\jython.bat Python Version: 2.5.1 Python Path: ['E:\\Programming\\Project\\django_app\\mysite', 'C:\\jython2.5.1\\Lib\\site-packages\\setuptools-0.6c11-py2.5.egg', 'C:\\jython2.5.1\\Lib', '__classpath__', '__pyclasspath__/', 'C:\\jython2.5.1\\Lib\\site-packages'] Server time: Mon, 12 Apr 2010 12:02:56 +0530

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• Decoupling the view, presentation and ASP.NET Web Forms

  - by John Leidegren

  I have an ASP.NET Web Forms page which the presenter needs to populate with controls. This interaction is somewhat sensitive to the page-life cycle and I was wondering if there's a trick to it, that I don't know about. I wanna be practical about the whole thing but not compromise testability. Currently I have this: public interface ISomeContract { void InstantiateIn(System.Web.UI.Control container); } This contract has a dependency on System.Web.UI.Control and I need that to be able to do things with the ASP.NET Web Forms programming model. But neither the view nor the presenter may have knowledge about ASP.NET server controls. How do I get around this? How can I work with the ASP.NET Web Forms programming model in my concrete views without taking a System.Web.UI.Control dependency in my contract assemblies? To clarify things a bit, this type of interface is all about UI composition (using MEF). It's known through-out the framework but it's really only called from within the concrete view. The concrete view is still the only thing that knows about ASP.NET Web Forms. However those public methods that say InstantiateIn(System.Web.UI.Control) exists in my contract assemblies and that implies a dependency on ASP.NET Web Forms. I've been thinking about some double dispatch mechanism or even visitor pattern to try and work around this.

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• Decoupling into DAL and BLL - my concerns.

  - by novice_man

  Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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• Coupling between controller and view

  - by cheez

  The litmus test for me for a good MVC implementation is how easy it is to swap out the view. I've always done this really badly due to being lazy but now I want to do it right. This is in C++ but it should apply equally to non-desktop applications, if I am to believe the hype. Here is one example: the application controller has to check some URL for existence in the background. It may connect to the "URL available" event (using Boost Signals) as follows: BackgroundUrlCheckerThread(Controller & controller) { // ... signalUrlAvailable.connect( boost::bind(&Controller::urlAvailable,&controller,_1)) } So what does Controller::urlAvailable look like? Here is one possibility: void Controller::urlAvailable(Url url) { if(!view->askUser("URL available, wanna download it?")) return; else // Download the url in a new thread, repeat } This, to me, seems like a gross coupling of the view and the controller. Such a coupling makes it impossible to implement the view when using the web (coroutines aside.) Another possibility: void Controller::urlAvailable(Url url) { urlAvailableSignal(url); // Now, any view interested can do what it wants } I'm partial to the latter but it appears that if I do this there will be: 40 billion such signals. The application controller can get huge for a non-trivial application A very real possibility that a given view accidentally ignores some signals (APIs can inform you at link-time, but signals/slots are run-time) Thanks in advance.

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• Book/tutorial that teaches how to make programs that are easy to maintain and are less coupled?

  - by grokker

  Hi, I'm a PHP programmer and I really want to increase the quality of my code and most importantly I want to be better at programming. What book, tutorial or article would you guys suggest that I read that teaches how to make programs that are less coupled and easy to maintain? Are there any specific tips for PHP especially for the CakePHP framework? Thanks in advance!

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• How to decouple an app's agile development from a database using BDUF?

  - by Rob Wells

  G'day, I was reading the article "Database as a Fortress" by Dan Chak from the excellent book "97 Things Every Software Architect Should Know" (sanitised Amazon link) which suggests that databases should not be designed using an agile approach. There's an SO question on agile approaches and databases "Agile development and database changes" which has some excellent answers covering agile development approaches. In fact, one of the answers supplies a brilliant idea of what's needed for each update of the DB. ;-) But after reading Dan Chak's article, I am left wondering if an agile approach is really suitable for large scale systems. This of course leads on to the question of how best to decouple an agile approach for the application that is interacting with the BDUF database design without adding complicated translation layers in the final design employed? Any suggestions? cheers,

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• a completely decoupled OO system ?

  - by shrini1000

  To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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• What is a good design pattern and terminology for decoupling output?

  - by User

  I have a program where I want to save some data record. And I want the output type to be flexible such that I could save the data record to a text file, xml file, database, push to a webservice. My take on it would be to create an interface such as DataStore with a Save() method, and the concrete subclasses such as TextFileDataStore, DatabaseDataStore, etc. What is the proper name/terminology for this type of pattern (I'm using the term "DataStore", log4net names things "appenders", .net they talk about "providers" and "persistence")? I want to come up with good class names (and method names) that fit with a convention if there is one. can you point me to a decent example, preferably in C#, C++, or java? Update Managed to find this stack overflow question, Object persistence terminology: 'repository' vs. 'store' vs. 'context' vs. 'retriever' vs. (…), which captures the terminology part of my question pretty well although there's not a decent answer yet.

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• Dependency Injection and method signatures

  - by sunwukung

  I've been using YADIF (yet another dependency injection framework) in a PHP/Zend app I'm working on to handle dependencies. This has achieved some notable benefits in terms of testing and decoupling classes. However,one thing that strikes me is that despite the sleight of hand performed when using this technique, the method names impart a degree of coupling. Probably not the best example -but these methods are distinct from ... say the PEAR Mailer. The method names themselves are a (subtle) form of coupling //example public function __construct($dic){ $this->dic = $dic; } public function example(){ //this line in itself indicates the YADIF origin of the DIC $Mail= $dic->getComponent('mail'); $Mail->setBodyText($body); $Mail->setFrom($from); $Mail->setSubject($subject); } I could write a series of proxies/wrappers to hide these methods and thus promote decoupling from , but this seems a bit excessive. You have to balance purity with pragmatism... How far would you go to hide the dependencies in your classes?

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• Routing in ASP.NET4

  Routing Allows us to build friendly URL's by decoupling the URL of the HTTP Request from the physical path of the web form that serves the Request.

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• Implementing the MVC Design Pattern in ASP.NET...

  Design patterns can help solve complex design problems if they are properly used. The main advantage of using the Model-View-Control (MVC) pattern is decoupling the business and the presentation layers....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Implementing the MVC Design Pattern in ASP.NET...

  Design patterns can help solve complex design problems if they are properly used. The main advantage of using the Model-View-Control (MVC) pattern is decoupling the business and the presentation layers....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Use controller in view in MVC

  - by gavri

  I have a problem convincing my team mates why we shouldn't use (directly reference) the controller in the view when developing components in the spirit of MVC. I have invoked decoupling and natural intuition, but still those arguments didn't get through. They say, in their defense, that this is a normal compromise. What arguments are convincing? Or they are right? How can the practice of using the controller in the view could affect a project on the long run?

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• Local Events | Azure Bootcamp

  - by Jeff Julian

  Coming to Kansas City April 8th and 9th is the Microsoft Azure Bootcamp. This event looks very promising for those developers who are looking into Azure for themselves or their companies. It covers the wide range of topics required to understand what Azure really is and is not. Space is limited so if you are considering Azure, register for this event today.Agenda:Module 1: Introduction to cloud computer and AzureHow it worksKey ScenariosThe development environment and SDKModule 2: Using Web RolesBasic ASP.NETBasic configurationModule 3: Blobs: File Storage in the cloudModule 4: Tables: Scalable hierarchical storageModule 5: Queues: Decoupling your systemsModule 6: Basic Worker RolesExecuting backend processesConsuming a queueLeveraging local storageModule 7: Advanced Worker RolesExternal EndpointsInter-role communicationModule 8: Building a business with AzureUsing Azure as an ISV or a partnerAdvantages to delivering valueBPOSPricingModule 9: SQL AzureSetting it upSQL Azure firewallRemote managementMigrating dataModule 10: AppFabricService BusAccess Control SystemIdentity in the cloudModule 11: Cloud ScenariosApp migration strategiesDisposable computingDynamic scaleShuntingPrototypingMultitenant applications (This is my second attempt at this post after MacJournal decided to crash and not save my work. Authoring tools all need auto-save features by now, that is a requirement set in stone by Microsoft Word 97) Related Tags: Azure, Microsoft, Kansas City

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• Getting to grips with the stack in nasm

  - by MarkPearl

  Today I spent a good part of my day getting to grips with the stack and nasm. After looking at my notes on nasm I think this is one area for the course I am doing they could focus more on… So here are some snippets I have put together that have helped me understand a little bit about the stack… Simplest example of the stack You will probably see examples like the following in circulation… these demonstrate the simplest use of the stack… org 0x100 bits 16 jmp main main: push 42h push 43h push 44h mov ah,2h ;set to display characters pop dx    ;get the first value int 21h   ;and display it pop dx    ;get 2nd value int 21h   ;and display it pop dx    ;get 3rd value int 21h   ;and display it int 20h The output from above code would be… DCB Decoupling code using “call” and “ret” This is great, but it oversimplifies what I want to use the stack for… I do not know if this goes against the grain of assembly programmers or not, but I want to write loosely coupled assembly code – and I want to use the stack as a mechanism for passing values into my decoupled code. In nasm we have the call and return instructions, which provides a mechanism for decoupling code, for example the following could be done… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h mov dx,41h int 21h ret ;---------------------------------------- main: call displayChar int 20h   This would output the following to the console A So, it would seem that call and ret allow us to jump to segments of our code and then return back to the calling position – a form of segmenting the code into what we would called in higher order languages “functions” or “methods”. The only issue is, in higher order languages there is a way to pass parameters into the functions and return results. Because of the primitive nature of the call and ret instructions, this does not seem to be obvious. We could of course use the registers to pass values into the subroutine and set values coming out, but the problem with this is we… Have a limited number of registers Are threading our code with tight coupling (it would be hard to migrate methods outside of their intended use in a particular program to another one) With that in mind, I turn to the stack to provide a loosely coupled way of calling subroutines… First attempt with the Stack Initially I thought this would be simple… we could use code that looks as follows to achieve what I want… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h pop dx int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h   However running this application does not give the desired result, I want an ‘A’ to be returned, and I am getting something totally different (you will to). Reading up on the call and ret instructions a discovery is made… they are pushing and popping things onto and off the stack as well… When the call instruction is executed, the current value of IP (the address of the instruction to follow) is pushed onto the stack, when ret is called, the last value on the stack is popped off into the IP register. In effect what the above code is doing is as follows with the stack… push 41h push current value of ip pop current value of ip to dx pop 41h to ip This is not what I want, I need to access the 41h that I pushed onto the stack, but the call value (which is necessary) is putting something in my way. So, what to do? Remember we have other registers we can use as well as a thing called indirect addressing… So, after some reading around, I came up with the following approach using indirect addressing… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h In essence, what I have done here is used a trick with the stack pointer… it goes as follows… Push 41 onto the stack Make the call to the function, which will push the IP register onto the stack and then jump to the displayChar label Move the value in the stack point to the bp register (sp currently points at IP register) Move the at the location of bp minus 2 bytes to dx (this is now the value 41h) display it, execute the ret instruction, which pops the ip value off the stack and goes back to the calling point This approach is still very raw, some further reading around shows that I should be pushing the value of bp onto the stack before replacing it with sp, but it is the starting thread to getting loosely coupled subroutines. Let’s see if you get what the following output would be? org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+4] int 21h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h push 42h call displayChar int 20h The output is… AB Where to from here? If by any luck some assembly programmer comes along and see this code and notices that I have made some fundamental flaw in my logic… I would like to know, so please leave a comment… appreciate any feedback!

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• Does it make sense to use ORM in Android development?

  - by Heinzi

  Does it make sense to use an ORM in Android development or is the framework optimized for a tighter coupling between the UI and the DB layer? Background: I've just started with Android development, and my first instinct (coming from a .net background) was to look for a small object-relational mapper and other tools that help reduce boilerplate clode (e.g. POJOs + OrmLite + Lombok). However, while developing my first toy application I stumbled upon a UI class that explicitly requires a database cursor: AlphabetIndexer. That made me wonder if maybe the Android library is not suited for a strict decoupling of UI and DB layer and that I will miss out on a lot of useful, time-saving features if I try to use POJOs everywhere (instead of direct database access). Clarification: I'm quite aware of the advantages of using ORM in general, I'm specifically interested in how well the Android class library plays along with it.

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• New to Java and Spring. What are some good design principles for an inexperienced java developer like me?

  - by Imtiaz Ahmad

  I am learning Java and have written a few small useful programs. I am new to spring but have managed to understand the concept of dependency injection for decoupling. I'm trying to applying that in my development work in an enterprise setting. What are the 3 most important design patterns I should master (not for interview purposes but ones that I will use every day in as a good java developer)? Also what are some good java design considerations and practices in coding specifically in Java? My goal is write good decoupled and coherent programs that are easy to maintain that don't make me standout as a java rookie. Stuff like not beginning my package names with com. have already made me precariously visible in my team. But they know I have 2 years of coding experience and its not in java.

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• Why were annotations introduced in Spring and Hibernate?

  - by Chandrashekhar

  I would like to know why were annotations introduced in Spring and Hibernate? For earlier versions of both the frameworks book authors were saying that if we keep configuration in xml files then it will be easier to maintain (due to decoupling) and just by changing the xml file we can re-configure the application. If we use annotations in our project and in future we want to re-configure application then again we have to compile and build the project. So why were these annotations introduced in these frameworks? From my point of view annotations make the apps dependent on certain framework. Isn't it true?

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• Using packages (gems, eggs, etc.) to create decoupled architectures

  - by Juan Carlos Coto

  The main issue Seeing the good support most modern programming platforms have for package management (think gem, npm, pip, etc), does it make sense to design an application or system be composed of internally developed packages, so as to promote and create a loosely coupled architecture? Example An example of this would be to create packages for database access, as well as for authentication and other components of the system. These, of course, use external packages as well. Then, your system imports and uses these packages - instead of including their code within its own code base. Considerations To me, it seems that this would promote code decoupling and help maintainability, almost in a Web-based-vs.-desktop-application kind of way (updates are applied almost automatically, single code base for single functionality, etc.). Does this seem like a rational and sane design concept? Is this actually used as a standard way of structuring applications today? Thanks very much!

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