This class is an implementation of the NSLocking protocol that provides a lock that may be acquired multiply by a single thread without creating a deadlock condition. See Chapter 2 for more information on how locking works.

@interface NSRecursiveLock : NSObject <NSLocking>
// Instance Methods
- (BOOL)lockBeforeDate:(NSDate *)limit;
- (BOOL)tryLock;
// Methods Implementing NSLocking
- (void)lock;
- (void)unlock;