NSDictionary 到 NSArray

 placeholderCopyNSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];  
NSArray *copiedArray = myDictionary.copy;

获取密钥：

 placeholderCopyNSArray *keys = [myDictionary allKeys];

获取价值：

 placeholderCopyNSArray *values = [myDictionary allValues];