[Swift] DAY14: Auto Reference count

Auto reference count

First to accompany her sister to see the film, Dot code to occupy a hole.

Weak references

It can be preceded by weak an indication that this is a weak reference. A weak reference does not hold the referenced instance, and it does not prevent the ARC from destroying the referenced instance.

You can see how to avoid circular references by using weak references in the following example:

classperson { LetNameString    varApartment:apartment? Init (Name:String{self.name = name} deinit {println ("\ (name) is being deinitialized")    }}classApartment { LetNumber:int weakvarTenant:person? Init (number:int) {self.number = number} deinit {println ("Apartment #\ (number) is being deinitialized")    }}varWhy:person?varnumber604:apartment?why = person (name:"Why") number604 = Apartment (number:604) why!. Apartment = number604number604!. Tenant = WHYPRINTLN ("Nil 1") Why = Nilprintln ("Nil 2") number604 = Nil

No master reference

It can be preceded by unowned an indication that this is a no-master reference. Similar to weak references, a no-master reference does not hold the referenced instance firmly. Unlike a weak reference, a non-primary reference is always valued. Therefore, no primary reference is always defined as a non-optional type.

The following example:

classCustomer { LetNameString    varCard:creditcard? Init (Name:String{self.name = name} deinit {println ("\ (name) is being deinitialized")    }}classCreditCard { LetNumber:int unowned LetCustomer:customer Init (Number:int, customer:customer) {self.number = number Self.customer = Customer } deinit {println ("Card #\ (number) is being deinitialized")    }}varJohn:customer?john = Customer (name:"Why") john!. Card = CreditCard (number:1234_5678_9012_3456, customer:john!) John = Nil

References

• Automatic Reference Counting

[Swift] DAY14: Auto Reference count