C# using Statement equivalent in Swift

Question

I'm very new to Swift language, I have a C# Background.

and I'm wondering if there is an equivalent code for C# using statement in swift Language

using( var a = new MyClass()){
//Code Here
}

Answer 1

Swift's automatic reference counting guarantees deterministic deinitalization (unlike the CLR's garbage collector), so you can put clean up code in your class' deinit method. This is exactly like RAII in C++. This technique works even if an exception is thrown.

class MyClass() {
    var db = openDBConnection() //example resource

    deinit() {
        db.close()
    }
}

func foo() {
    var a = MyClass()
    print(a) // do stuff with a

    // the (only) reference, a, will go out of scope,
    // thus the instance will be deinitialized.
}

You can also use a defer statement:

var a = MyClass()
defer { a.cleanUp() /* cleanup a however you wish */ }

You lose the standardization of using an Interface like IDisposable, but you gain generality in being able to execute whatever code you wish.

Answer 2

Just learning Swift and came up with the same question.

The closest I could get was this:

   if let UOW = (try UnitOfWork() as UnitOfWork?)
   {


   }

It's a bit of a hack on optional binding but seems to work. You will need to make sure your class has a deinit defined as called out above by Alexander. I found that even if my init throws an exception, the deinit method is still called as soon as you go out of scope on the IF statement.

NOTE: Make sure you are using weak references if applicable to make sure your deinit actually gets called!

It is probably more Swifty to use a DO block for your scoping:

do
{
    let UOW = try UnitOfWork()
    // your code here
}

Which has the benefit of avoiding a "pyramid of doom" with your pseudo using blocks (like you'll get in c#)