黑马程序员------英语面试问题整理

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Q: Is the delegate for a CAAnimation retained? 
A: Yes it is!! This is one of the rare exceptions to memory management rules.

Q: What happens when the following code executes?

Ball *ball = [[[[Ball alloc] init] autorelease] autorelease]; 

A: It will crash because it’s added twice to the autorelease pool and when it dequeued the autorelease pool calls release more than once. 

Q: Outline the class hierarchy for a UIButton until NSObject. 

A: UIButton inherits from UIControl, UIControl inherits from UIView, UIView inherits from UIResponder, UIResponder inherits from the root class NSObject

Q: Explain the difference between NSOperationQueue concurrent and non-concurrent. 
A: In the context of an NSOperation object, which runs in an NSOperationQueue, the terms concurrent and non-concurrent do not necessarily refer to the side-by-side execution
of threads. Instead, a non-concurrent operation is one that executes using the environment that is provided for it while a concurrent operation is responsible for setting up its own execution environment.


Q: Implement your own synthesized methods for the property NSString *title. 
A: Well you would want to implement the getter and setter for the title object. Something like this:

 

-（NSString *）title{

    return title;

}

- (void) setTitle:(NSString*) newTitle{

  if (newTitle !=title) {

       [title release];

       title = [newTitle retain]; / or copy, depending on your needs

     }

}

Q: Implement the following methods: retain, release, autorelease.

A: 

-(id)retain{

     NSIncrementExtraRefCount(self);

     retain self;

}

-(void) release {

    if (NSDecremetExtraRefCountWasZero(self)) {

     NSDeallocateObject(self);

    }

}

-(id)auotrelease {

  // add the object to the autorelease pool

    [NSAutoreleasePool addObject:self];

    return self;

}