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Add automatic reference counting examples.

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Levi Bostian 2013-12-31 14:04:07 -06:00
parent dff26a28af
commit 8e04611520
1 changed files with 15 additions and 0 deletions
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@ -405,6 +405,21 @@ MyClass *newVar = [classVar retain]; // If classVar is released, object is still
@property (retain) MyClass *instance; // Release old value and retain a new one (strong reference).
@property (assign) NSSet *set; // Pointer to new value without retaining/releasing old (weak reference).
// Because memory management can be a pain, Xcode 4.2 and iOS 4 introduced Automatic Reference Counting (ARC).
// ARC is a compiler feature that inserts retain, release, and autorelease automatically for you, so when using ARC,
// you must not use retain, relase, or autorelease.
MyClass *arcMyClass = [[MyClass alloc] init]; // Without ARC, you will need to call: [arcMyClass release] after
// you're done using arcMyClass. But with ARC, there is no need. It will insert this release statement for you.
// As for the "assign" and "retain" @property attributes, with ARC you use "weak" and "strong".
@property (weak) MyClass *weakVar; // weak does not take ownership of object. If original instance's reference count
// is set to zero, weakVar will automatically receive value of nil to avoid application crashing.
@property (strong) MyClass *strongVar; // strong takes ownership of object. Ensures object will stay in memory to use.
// For regular variables (not @property declared variables), use the following:
__strong NSString *strongString; // Default. Variable is retained in memory until it leaves it's scope.
__weak NSSet *weakSet; // Weak reference to existing object. When existing object is released, weakSet is set to nil.
__unsafe_unretained NSArray *unsafeArray; // Like __weak but unsafeArray not set to nil when existing object is released.
```
## Further Reading