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What is strong reference and weak reference in Objective C?
Objective-C uses reference counting to manage the memory of its objects through the concept of object ownership. There are two types of object reference: Strong references, which keep an object “alive” in memory. Weak references, which have no effect on the lifetime of a referenced object.
What’s a weak reference when would you want to use one?
A weak reference permits the garbage collector to collect the object while still allowing the application to access the object. A weak reference is valid only during the indeterminate amount of time until the object is collected when no strong references exist.
What is weak and strong reference?
A weak reference is just a pointer to an object that doesn’t protect the object from being deallocated by ARC. While strong references increase the retain count of an object by 1, weak references do not. In addition, weak references zero out the pointer to your object when it successfully deallocates.
Why do you need weak references?
As stated by Java documentation, weak references are most often used to implement canonicalizing mappings. A mapping is called canonicalized if it holds only one instance of a particular value. It’s the implementation of the Map interface where every key is stored as a weak reference to the given key.
What is the difference between weak and strong?
The key difference between a strong and a weak or unowned reference is that a strong reference prevents the class instance it points to from being deallocated. In other words, weak and unowned references cannot prevent a class instance from being deallocated.
What is the difference between strong and weak references in C#?
The difference between a weak and a strong reference to an object is that while the former still allows the garbage collector to reclaim the memory occupied by that object, a strong reference to an object doesn’t allow the garbage collector to reclaim the memory occupied by that object if the object is reachable.
What is a strong reference?
Strong References: This is the default type/class of Reference Object. Any object which has an active strong reference are not eligible for garbage collection. The object is garbage collected only when the variable which was strongly referenced points to null.
Where are weak references used?
WeakReferences are best used in cases where there will be other references to the object, but you can’t (or don’t want to have to) detect when those other references are no longer used.
How do you implement a weak reference?
How are weak references implemented?
- “Intrusive” – to add list of weak references to the most top class (object class).
- “Non-intrusive” – to maintain a hashtable of objects’ pointers to lists of weak references.
- “Dirty” – to store a special hash-value with each object, which would be zeroed when the object is destroyed.
What is a weak objective?
weak: will assign the incoming value to it without retaining it. So the basic difference is the retaining of the new variable. Generaly you want to retain it but there are situations where you don’t want to have it otherwise you will get a retain cycle and can not free the memory the objects.
What is weak reference in C#?
What is a weak reference in programming?
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector, unlike a strong reference.