面试题4

58.
线程之间怎么通信?

59. 线程生产者,消费者如何实现?

1 个线程是生产者,一个是消费者如何实现这个模型.

NSMutableArray *dataList;NSLock *dataLock;

- (void) produceAndConsume {

dataList = [[NSMutableArray alloc] init];

dataLock = [[NSLock alloc] init];

[NSThread detachNewThreadSelector:@selector(produce:) toTarget:self withObject:nil];[NSThread detachNewThreadSelector:@selector(consume:) toTarget:self withObject:nil];

}

- (void) produce:(id)arg {

int index = 0;while (1) {

NSNumber *n = [NSNumber numberWithInt:index++];[dataLock lock];

[dataList addObject:n];

[NSThread sleepForTimeInterval:0.5];

}}

- (void) consume:(id)arg {while (1) {

if ([dataList count] > 0) {[dataLock lock];

id obj = [dataList objectAtIndex:0];[dataList removeObject:0];[dataLock unlock];

NSLog(@"消费
obj %@", obj);

}

[NSThread sleepForTimeInterval:1];}

}

60.
不同屏幕怎么适配

iphone, iphone3G, iphone3GS 320x480

iphone4, iphoen4S 640x960 retina

iphone5, iphone5S, 640x1136

写程序需要有 2
套图片 demo.png demo@2x.pngiphone5
适配.

1136/2-44-49

[[UIScreen
mainScreen]
applicationFrame] = (320x460, 320x548)[[UIScreen
mainScreen]
bounds] = (320x480, 320x568)

iPad, iPad2, iPad Mini 1024x768

iPad3, iPad4, 2048x1563

61.
不同版本屏幕旋转怎么适配62.
内存警告应该怎么做

尽量多的释放内存。把一些内容写到文件中,不要保存在内存中。63. iOS5, iOS6, iOS7
区别

64. NSNotification
是同步还是异步的

是同步的.
如果需要异步 必须使用
NSNotificationQueue
实现

A notification center delivers notifications to observers synchronously. In other words, thepostNotification: methods do not return until all observers have received and processed thenotification.
To send notifications asynchronously use NSNotificationQueue.

In a multithreaded application, notifications are always delivered in the thread in which thenotification was posted, which may not be the same thread in which an observer registereditself.

Hope it helps you.