What is the difference between a var and a weak var in Swift?
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Luca Angeletti
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5[How much research effort is expected of Stack Overflow users?](http://meta.stackoverflow.com/questions/261592/how-much-research-effort-is-expected-of-stack-overflow-users) – Martin R Apr 05 '15 at 20:09
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This has to do with how ARC manages memory of your objects.
Using var defines a strong reference to the object, while using weak var defines a weak reference to the object.
Objects are kept in memory for as long as there remains one or more strong references to that object. Using a weak reference allows you to hold a reference to an object without increasing what is known as its "retain count".
If nothing else holds a reference to your weak var, the object will be deallocated, and your weak var will decay to nil.1 This won't happen when you just use var, as this defines a strong reference to the object, which should prevent it from deallocating.
This is identical to how "strong" vs "weak" works in Objective-C, and I recommend you read this answer, as it applies exactly to Swift.
1As a Swift specific note, this is the reason why anything declared as a weak var must be an optional type.
