Skip to main content

Single Responsibility Principle

Toata lumea a auzit de acest principiu. Pe scurt fiecare obiect trebuie sa aibe o singura responsabilitate.
Problema apare la interpretare. Fiecare persoana poate sa inteleaga diferit cand ne referim la responsabilitate.
Din cate am vazut pana acuma exista doua moduri in care se poate implementa SRP:
- fiecare metoda publica expusa de catre o clasa reprezinta o responsabilitate unica;
- fiecare obiect ar trebui sa aibe o singura responsabilitate.
Daca ne folosim de prima varianta, ajungem sa avem sute de interfete si clase abstracte, fiecare cu o singura metoda. In cazul in care respectam a doua varianta apare problema la interpretare. Cum putem spune ca o clasa are o singura responsabilitate si doar una.
De exemplu daca avem o entitate la care vrem sa adaugam metoda ToXml() am putea spune ca este corect din punct de vederea a SRP. Dar mai tarziu poate am avea nevoie de metoda ToString(). Aceste doua metode violeaza SRP.
Din pacate aceasta discutie ar putea sa continue la nesfarsit. Trebuie gasita un echilibru.
Pentru exemplul dat mai sus putem sa adaugam o metoda To() care prin intermediul unui formater sa ne returneze obiectul in formatul pe care il dorim.
Referinte: http://www.objectmentor.com/resources/articles/srp.pdf

Comments

  1. Din pacate multi programatori nu au auzit de acest principiu.. Chestia cu o singura metoda publica per clasa e clar o exagerare - Robert Martin (cel care a formulat principiul sub acest nume) explica ca prin 'responsabilitate' intelege 'reason to change'.

    Multe exemple care le da sunt voit exagerate un pic pentru a accentua ideea - ceea ce merita retinut din SRP e necesitatea de a evita aparitia de "god classes" care fac totul pentru toata lumea.
    Doar cine a avut de lucrat cu astfel de clase de baza, care combinau totul de la UI, business logic pana la persistenta, cu sute de metode publice si zeci de mii de linii de cod intelege cu adevarat importanta principiului - problema nu e la clasele cu 2-3 metode ce tin de acelasi layer si acelasi domain concept..

    ReplyDelete

Post a Comment

Popular posts from this blog

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

Fundamental Books of a Software Engineer (version 2018)

More then six years ago I wrote a blog post about fundamental books that any software engineer (developer) should read. Now it is an excellent time to update this list with new entries.

There are 5 different categories of books, that represent the recommended path. For example, you start with Coding books, after that, you read books about Programming, Design and so on.
There are some books about C++ that I recommend not because you shall know C++, only because the concepts that you can learn from it.

Coding

Writing solid codeCode completeProgramming Pearls, more programming pearls(recommended)[NEW] Introduction to Algorithms

Programming

Refactoring (M. Fowler)Pragmatic ProgrammerClean code[NEW] Software Engineering: A Practitioner's Approach[NEW] The Mythical Man-Month[NEW] The Art of Computer Programming

Design

Applying UML and Patterns (GRASP patterns)C++ coding standards (Sutter, Alexandrescu)The C++ programming language (Stroustrup, Part IV)Object-oriented programming (Peter Coad)P…