On 5/27/16 4:20 PM, chmike wrote:
I need to create an app wide singleton instance for my class. The singleton is immutable, but I want to allow mutable references to that singleton object so that I can do fast 'is' tests.I declared this class Category { protected static immutable Category instance_ = new Category; Category instance() { return cast(Category)instance_; } ... } It compiles and the instance should be instantiated at compile time. I couldn't check yet. The public interface of Category is designed so that the object's state can't be modified and thus remains immutable. Is this code valid D or is the behavior undefined due to the cast ?
You can cast away immutable. You just can't mutate. Hard to say without seeing what the ... is.
A variant implementation would have a method that modifies the object but only internally and in a very controlled way to store strings in a cache for faster access. Would it still be valid D code ?
No. Undefined behavior if you modify immutable data. -Steve
