> On Nov 4, 2016, at 2:57 AM, Anton Mironov via swift-dev <swift-dev@swift.org>
> wrote:
>
> Hi all,
>
> I want to initialize constant object graph with cycles. I've considered two
> workarounds, but this is not a way I want it to be.
>
> Here is an example:
> ```
> // I have a context
> protocol Context : class {
> /* some */
> }
>
> // I have an object that has sense only in context
> class ObjectInContext {
> private weak var context: Context?
>
> init(context: Context) {
> self.context = context
> }
> }
>
> // This is what I want to do
> // The object graph has a cycle, but there is no a retain cycle
> class ContextA : Context {
> let object: ObjectInContext
>
> init() {
> self.object = ObjectInContext(context: self) // this code will not compile
> for many good reasons
> }
> }
>
> // This is workaround #1
> // It looks bad for 2 reasons: implicitly unwrapped optional, it is easy to
> forget to initialize object
> class ContextB : Context {
> var object: ObjectInContext!
>
> init() {
> self.object = ObjectInContext(context: self)
> }
> }
The IUO is the typical pattern here.
Forgetting to initialize an IUO is less of a problem than it would be in C or
ObjC. Access to an IUO is checked at runtime. If you forget to initialize
self.object then the process will deliberately halt the first time you try to
use it.
--
Greg Parker gpar...@apple.com <mailto:gpar...@apple.com> Runtime
Wrangler
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