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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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  • I loose some directories when i upgrade from Ubuntu 11.10 to 12.04

    - by maythux
    last day i upgraded my ubunut 11.10 desktop to ubuntu 12.04. I was running a KVM virtual about 7 machines and managed by virt-manage software.... anyway when i finished upgrading i found that virt-manager is not working so i have to reconfigure it again and install some other missing packages that was deleted!!!! anyway i solve this issue...then i started to restore my virtual machines i restore 2 machines without any problems the third and fourth ones (windows) make a check disk that takes more that 6 hours but finally it works... other machines i cant find their attached hard disks i don't know what happens but i cant found that files. 1- upgrading delete files!?!! 2- Is there anyway to restore those files? thanks in advance

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  • Loose Coupling vs. Information Hiding and Ease of Change

    - by cretzel
    I'm just reading Code Complete by Steve McConell and I'm thinking of an Example he gives in a section about loose coupling. It's about the interface of a method that calculates the number of holidays for an employee, which is calculated from the entry date of the employee and her sales. The author suggests a to have entry date and sales as the parameters of the method instead of an instance of the employee: int holidays(Date entryDate, Number sales) instead of int holidays(Employee emp) The argument is that this decouples the client of the method because it does not need to know anything about the Employee class. Two things came to my mind: Providing all the parameters that are needed for the calculation breaks encapsulation. It shows the internals of the method on how it computes the result. It's harder to change, e.g. when someone decides that also the age of the employee should be included in the calculation. One would have to change the signature. What's your opinion?

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  • Git: corrupt loose object

    - by NeoRiddle
    I was trying to merge my master branch with another one called pull-stage, but Git throws me this error: error: inflate: data stream error (invalid distance too far back) error: corrupt loose object '5a63450f4a0b72abbc1221ccb7d9f9bfef333250' fatal: loose object 5a63450f4a0b72abbc1221ccb7d9f9bfef333250 (stored in .git/objects/5a/63450f4a0b72abbc1221ccb7d9f9bfef333250) is corrupt How can I solve this issue? I have reviewed other posts, but with no successful results: How to replace corrupt Git objects with new ones created from my files, which are fine Git: "Corrupt loose object" Corrupted Git Repository (data stream error)

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  • How to skip "Loose Object" popup when running 'git gui'

    - by Michael Donohue
    When I run 'git gui' I get a popup that says This repository currently has approximately 1500 loose objects. It then suggests compressing the database. I've done this before, and it reduces the loose objects to about 250, but that doesn't suppress the popup. Compressing again doesn't change the number of loose objects. Our current workflow requires significant use of 'rebase' as we are transitioning from Perforce, and Perforce is still the canonical SCM. Once Git is the canonical SCM, we will do regular merges, and the loose objects problem should be greatly mitigated. In the mean time, I'd really like to make this 'helpful' popup go away.

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  • Do complex JOINs cause high coupling and maintenance problems ?

    - by ashkan.kh.nazary
    Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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  • Does complex JOINs causes high coupling and maintenance problems ?

    - by ashkan.kh.nazary
    Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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  • Scenario to illustrate how unit testing leads to better design

    - by Cocowalla
    For an internal training session, I'm trying to come up with a simple scenario that illustrates how unit testing leads to better design, by forcing you to think about things like coupling before you start coding. The idea is that I get the participants to code something first, without considering unit testing, then we do it again, but considering unit testing. Hopefully the code produced second time round should be more decoupled and maintainable. I'm struggling to come up with a scenario that can be coded quickly, yet can still demonstrate how unit testing can lead to better overall design.

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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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  • Is loose coupling w/o use cases an anti-pattern?

    - by dsimcha
    Loose coupling is, to some developers, the holy grail of well-engineered software. It's certainly a good thing when it makes code more flexible in the face of changes that are likely to occur in the foreseeable future, or avoids code duplication. On the other hand, efforts to loosely couple components increase the amount of indirection in a program, thus increasing its complexity, often making it more difficult to understand and often making it less efficient. Do you consider a focus on loose coupling without any use cases for the loose coupling (such as avoiding code duplication or planning for changes that are likely to occur in the foreseeable future) to be an anti-pattern? Can loose coupling fall under the umbrella of YAGNI?

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  • Which approach is the most maintainable?

    - by 2rs2ts
    When creating a product which will inherently suffer from regression due to OS updates, which of these is the preferable approach when trying to reduce maintenance cost and the likelihood of needing refactoring, when considering the task of interpreting system state and settings for a lay user? Delegate the responsibility of interpreting the results of inspecting the system to the modules which perform these tasks, or, Separate the concerns of interpretation and inspection into two modules? The first obviously creates a blob in which a lot of code would be verbose, redundant, and hard to grok; the second creates a strong coupling in which the interpretation module essentially has to know what it expects from inspection routines and will have to adapt to changes to the OS just as much as the inspection will. I would normally choose the second option for the separation of concerns, foreseeing the possibility that inspection routines could be re-used, but a developer updating the product to deal with a new OS feature or something would have to not only write an inspection routine but also write an interpretation routine and link the two correctly - and it gets worse for a developer who has to change which inspection routines are used to get a certain system setting, or worse yet, has to fix an inspection routine which broke after an OS patch. I wonder, is it better to have to patch one package a lot or two packages, each somewhat less so?

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  • Where should you put constants and why?

    - by Tim Meyer
    In our mostly large applications, we usually have a only few locations for constants: One class for GUI and internal contstants (Tab Page titles, Group Box titles, calculation factors, enumerations) One class for database tables and columns (this part is generated code) plus readable names for them (manually assigned) One class for application messages (logging, message boxes etc) The constants are usually separated into different structs in those classes. In our C++ applications, the constants are only defined in the .h file and the values are assigned in the .cpp file. One of the advantages is that all strings etc are in one central place and everybody knows where to find them when something must be changed. This is especially something project managers seem to like as people come and go and this way everybody can change such trivial things without having to dig into the application's structure. Also, you can easily change the title of similar Group Boxes / Tab Pages etc at once. Another aspect is that you can just print that class and give it to a non-programmer who can check if the captions are intuitive, and if messages to the user are too detailed or too confusing etc. However, I see certain disadvantages: Every single class is tightly coupled to the constants classes Adding/Removing/Renaming/Moving a constant requires recompilation of at least 90% of the application (Note: Changing the value doesn't, at least for C++). In one of our C++ projects with 1500 classes, this means around 7 minutes of compilation time (using precompiled headers; without them it's around 50 minutes) plus around 10 minutes of linking against certain static libraries. Building a speed optimized release through the Visual Studio Compiler takes up to 3 hours. I don't know if the huge amount of class relations is the source but it might as well be. You get driven into temporarily hard-coding strings straight into code because you want to test something very quickly and don't want to wait 15 minutes just for that test (and probably every subsequent one). Everybody knows what happens to the "I will fix that later"-thoughts. Reusing a class in another project isn't always that easy (mainly due to other tight couplings, but the constants handling doesn't make it easier.) Where would you store constants like that? Also what arguments would you bring in order to convince your project manager that there are better concepts which also comply with the advantages listed above? Feel free to give a C++-specific or independent answer. PS: I know this question is kind of subjective but I honestly don't know of any better place than this site for this kind of question. Update on this project I have news on the compile time thing: Following Caleb's and gbjbaanb's posts, I split my constants file into several other files when I had time. I also eventually split my project into several libraries which was now possible much easier. Compiling this in release mode showed that the auto-generated file which contains the database definitions (table, column names and more - more than 8000 symbols) and builds up certain hashes caused the huge compile times in release mode. Deactivating MSVC's optimizer for the library which contains the DB constants now allowed us to reduce the total compile time of your Project (several applications) in release mode from up to 8 hours to less than one hour! We have yet to find out why MSVC has such a hard time optimizing these files, but for now this change relieves a lot of pressure as we no longer have to rely on nightly builds only. That fact - and other benefits, such as less tight coupling, better reuseability etc - also showed that spending time splitting up the "constants" wasn't such a bad idea after all ;-)

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  • Loose component cables causing HDMI video problems

    - by jwir3
    I'm not sure this is the correct forum, but I'll ask anyway. I have an A/V setup at home that has something like the following: Five Components (actually a few more, like a CD player, but they don't really relate to this question): Older Pioneer Receiver Digital Set Top Box Sony BluRay Player Samsung Plasma TV Speakers The reason for the receiver is so that all the sound can go through the speakers, rather than some going to the TV speakers and some to the external speakers. They are connected as follows: Digital Set Top Box connects via component video to Samsung TV directly via Component 2 (audio goes to Older Pioneer Receiver). Sony BluRay player is connected via HDMI 1 to TV, but audio goes to the receiver. Now, the problem I'm having is that when I have the digital set top box connected, there are times when the Netflix or Hulu streams I watch through the Sony BluRay player (it's connected to a router for internet access) will lose video. What I mean by this is that the sound of the episode will keep playing, but the screen will go black. If I jiggle the component cables, it will often come back. If I disconnect the component cables, it will always come back. I've noticed that one of the connections (the red component cable) doesn't like to sit very well in the component socket in the back of the digital set top box. It seems like there is a bad connection here, but it doesn't seem like this should be affecting the HDMI input at all. What I've noticed, though, is that when I disconnect the digital set top box completely (i.e. remove the component cable from the back of the TV), the problem seems to resolve itself. I'm not talking about actually removing the cable physically, because I thought perhaps the cables were mashing against one another, and possibly jiggling each other loose. To correct this possible problem, I took the component cable completely out of the cable ties it was in in the back of my entertainment center, as well as pulled the digital set top box out from the entertainment center altogether. It's now connected directly to the TV, without any other cables touching it to cause some kind of weird interference or just physical pulling on the cable. Same problem. If, however, I disconnect the component cable and just leave it sitting behind the TV, then the problem goes away. So, my question is this - what could be causing this? Is it a case where it's an improperly shielded component cable that's causing interference with the HDMI input, or something that's wrong with the TV? It's an intermittent problem, so it's difficult to track down. The TV isn't that old, so it's probably still under warranty. I'm just wondering if there is something else I can do that might reduce this problem without having to haul a massive television set out of my house to get repaired/replaced.

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  • Good patterns for loose coupling in Java?

    - by Eye of Hell
    Hello. I'm new to java, and while reading documentation so far i can't find any good ways for programming with loose coupling between objects. For majority of languages i know (C++, C#, python, javascript) i can manage objects as having 'signals' (notification about something happens/something needed) and 'slots' (method that can be connected to signal and process notification/do some work). In all mentioned languages i can write something like this: Object1 = new Object1Class(); Object2 = new Object2Class(); Connect( Object1.ItemAdded, Object2.OnItemAdded ); Now if object1 calls/emits ItemAdded, the OnItemAdded method of Object2 will be called. Such loose coupling technique is often referred as 'delegates', 'signal-slot' or 'inversion of control'. Compared to interface pattern, technique mentioned don't need to group signals into some interfaces. Any object's methods can be connected to any delegate as long as signatures match ( C++Qt even extends this by allowing only partial signature match ). So i don't need to write additional interface code for each methods / groups of methods, provide default implementation for interface methods not used etc. And i can't see anything like this in Java :(. Maybe i'm looking a wrong way?

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  • Architecture Best Practice (MVC): Repository Returns Object & Object Member Accessed Directly or Repository Returns Object Member

    - by coderabbi
    Architecturally speaking, which is the preferable approach (and why)? $validation_date = $users_repository->getUser($user_id)->validation_date; Seems to violate Law of Demeter by accessing member of object returned by method call Seems to violate Encapsulation by accessing object member directly $validation_date = $users_repository->getUserValidationDate($user_id); Seems to violate Single Responsibility Principle as $users_repository no longer just returns User objects

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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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  • Sequential coupling in code

    - by dotnetdev
    Hi, Is sequential coupling (http://en.wikipedia.org/wiki/Sequential_coupling) really a bad thing in code? Although it's an anti-pattern, the only risk I see is calling methods in the wrong order but documentation of an API/class library with this anti-pattern should take care of that. What other problems are there from code which is sequential? Also, this pattern could easily be fixed by using a facade it seems. Thanks

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  • Loose Coupling of Components

    - by David
    I have created a class library (assembly) that provides messaging, email and sms. This class library defines an interface IMessenger which the classes EmailMessage and SmsMessage both implement. I see this is a general library that would be part of my infrastructure layer and would / can be used across any development. Now, in my application layer I have a class that requires to use a messaging component, I obviously want to use the messaging library that I have created. Additionally, I will be using an IoC container (Spring.net) to allow me to inject my implementation i.e. either email or sms. Therefore, I want to program against an interface in my application layer class, do I then need to reference my message class library from my application layer class? Is this tightly coupling my application layer class to my message class library? Should I be defining the interface - IMessenger in a seperate library? Or should I be doing something else?

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  • How exactly does dependency injection reduce coupling?

    - by dotnetdev
    Hi, I've done plenty of reading on Dependency Injection, but I have no idea, how does it actually reduce coupling? The analogy I have of DI is that all components are registered with a container, so theyre are like in a treasure chest. To get a component, you obviously register it first, but then you would have to interrogate the treasure chest (which is like a layer of indirection). Is this the right analogy? It doesn't make obvious how the "injection" happens, though (how would that fit in with this analogy?). Thanks

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  • Calling services from the Orchestrating layer in SOA?

    - by Martin Lee
    The Service Oriented Architecture Principles site says that Service Composition is an important thing in SOA. But Service Loose Coupling is important as well. Does that mean that the "Orchestrating layer" should be the only one that is allowed to make calls to services in the system? As I understand SOA, the "Orchestrating layer" 'glues' all the services together into one software application. I tried to depict that on Fig.A and Fig.B. The difference between the two is that on Fig.A the application is composed of services and all the logic is done in the "Orchestrating layer" (all calls to services are done from the "Orchestrating layer" only). On Fig.B the application is composed from services, but one service calls another service. Does the architecture on Fig.B violate the "Service Loose Coupling" principle of SOA? Can a service call another service in SOA? And more generally, can the architecture on Fig.A be considered superior to the one on Fig.B in terms of service loose coupling, abstraction, reusability, autonomy, etc.? My guess is that the A architecture is much more universal, but it can add some unnecessary data transfers between the "Orchestrating layer" and all the called services.

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  • Loose coupling of COM in C# or How to avoid COMException 0x80040154

    - by user283318
    I have a .Net 2 C# application I am developing which uses a VB 6 generated COM DLL. The VB DLL is updated frequently any my application crashes with a System.Runtime.InteropServices.COMException (0x80040154). The part of the COM DLL I use does not change but the version (and CLSID) will. The "Specific Version" option for the reference is false. The WrapperTool is tlbimp. How do I tell my application not to worry about changes in the DLL? Is there any way of checking just the functions I am using?

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