假設(shè)對(duì)象A具有一個(gè)屬性：@property (nonatomic, strong) Foo * bar;在實(shí)現(xiàn)中綜合為：@synthesize bar = _bar;對(duì)象B操作a Foo **，如本例中從對(duì)象A進(jìn)行的調(diào)用：Foo * temp = self.bar;[objB doSomething:&temp];self.bar = temp;是否可以合法地進(jìn)行此操作？該doSomething:方法的正確聲明是什么？此外，假設(shè)在我有機(jī)會(huì)設(shè)置屬性之前，對(duì)象B可能已被釋放bar（從而獲得所指向的實(shí)例的所有權(quán)temp）-我將如何告訴ARC移交擁有的引用？換句話說，如果我希望以下示例代碼起作用，我將如何處理ARC問題？Foo * temp = self.bar;    // Give it a reference to some current value[objB doSomething:&temp]; // Let it modify the referenceself.bar = nil;           // Basically release whatever we have_bar = temp;              // Since we're getting back an owning reference, bypass setter我在想什么呢編輯基于@KevinBallard的回答，我只想確認(rèn)我的理解。它是否正確？對(duì)象A：@implementation ObjectA@synthesize bar = _bar;- (void)someMethod{    ObjectB * objB = [[ObjectB alloc] initWithFoo:&_bar];    // objB handed off somewhere and eventually it's "doSomething" method is called.}@end對(duì)象B：@implementation ObjectB{    Foo * __autoreleasing * _temp;}- (id)initWithFoo:(Foo * __autoreleasing *)temp{    id self = [super init];    if (self)    {        _temp = temp;    }    return self;}- (void)doSomething{    ...    *_temp = [[Foo alloc] init];     ...}@end這將產(chǎn)生一個(gè)編譯時(shí)錯(cuò)誤： passing address of non-local object to __autoreleasing parameter for write-back