Best practice for resolving in Spring4D?

Question

In the spring4d demos, ServiceLocator.GetService<MyType>('Name') is used to resolve the types. But why not use GlobalContainer.Resolve<MyType>('Name') ? I don't see any advantage in this approach...

Answer 1

There is one use case, where I use ServiceLocator: when coding to make legacy code projects unit-testable...

There is an old project, where in mulitiple places, there are constructor calls of an object, which I write tests for (new and changed methods only, in classes, where injection is not possible, eg when a Form is created and destroyed in a button event).

In unit-tests, spring4d is helpful to instantiate the class-under-test:

I can use the GlobalContainer in the dpr for the production project and a special (test-only) TContainer-object which is constructed in Testfixture.Setup and destroyed in Testfixture.TearDown... I also re-initialize the global Service-Locator to use my Test-Container (Reason: I have bad experiences to use GlobalContainer in Test, you cannot un-register a type from GlobalContainer in Testfixture.TearDown).

So now, I got a big method in the dpr, where I register all types to GlobalContainer in the production-code project. In the Setup-Method of my test-fixture-class, I register all types needed for the test to my Testing-Container. And in the Methods, that I changed to make them unit-testable, I construct the classes-under-test with ServiceLocator, where formerly constructor-calls where used.

For me, it is the only way to make such a legacy-code project unit-testable... But my strategic goal is to replace most of this code (part-by-part, including the re-initialized ServiceLocators) one day. It is just not possible to replace it now (too much costs, too much risk...).