IOS, ARC, Property: (readwrite, nonatomic) vs (radwrite, retain, nonatomic)

Question

I am have read up some tutorials on ARC and am still left a bit confused on properties declarations. I wrote most most my code using the following pattern:

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Answer 1

ARC is will retain object based on the property declaration, you should use strong for properties that need to be retained and weak for properties that do not need to be retained.

weak properties are also nilled when the object is deallocated.

The compiler will always assume that properties are readwrite so there is no need to declare then this way.

@property (strong, nonatomic) PlayerData* playerData;
@property (strong, nonatomic) MusicLayer* musicLayer;
// Need use assign since strong is for objects only.
@property (assign, nonatomic) bool isPowerUpAvailable;