Currently I'm trying to understand dependency injection better and I'm using asp.net MVC to work with it. You might see some other related questions from me ;)
Alright, I'll start with an example controller (of an example Contacts Manager asp.net MVC application)
public class ContactsController{
ContactsManagerDb _db;
public ContactsController(){
_db = ContactsManagerDb();
}
//...Actions here
}
Allright, awesome that's working. My actions can all use the database for CRUD actions. Now I've decided I wanted to add unit testing, and I've added another contructor to mock a database
public class ContactsController{
IContactsManagerDb _db;
public ContactsController(){
_db = ContactsManagerDb();
}
public ContactsController(IContactsManagerDb db){
_db = db;
}
//...Actions here
}
Awesome, that's working to, in my unit tests I can create my own implementation of the IContactsManagerDb and unit test my controller.
Now, people usually make the following decision (and here is my actual question), get rid of the empty controller, and use dependency injection to define what implementation to use.
So using StructureMap I've added the following injection rule:
x.For<IContactsManagerDb>().Use<ContactsManagerDb>();
And ofcourse in my Testing Project I'm using a different IContactsManagerDb implementation.
x.For<IContactsManagerDb>().Use<MyTestingContactsManagerDb>();
But my question is, **What problem have I solved or what have I simplified by using dependency injection in this specific case"
I fail to see any practical use of it now, I understand the HOW but not the WHY? What's the use of this? Can anyone add to this project perhaps, make an example how this is more practical and useful?
MyTestinContactsManagerDb– Bedstead