应用开发中的地址簿功能实现

### 应用开发中的地址簿功能实现 在应用开发过程中，涉及到地址簿功能时，会有多个关键环节需要处理，包括发送响应、命令处理、访问远程地址簿等。下面将详细介绍这些方面的实现。 #### 1. 发送响应 在处理传入数据后，发送响应是一个重要步骤。借助`dispatch_io`，发送响应变得相对简单，只需调用一次`dispatch_io_write()`方法即可。以下是发送数据的代码示例： ```objc - (void) sendData: (NSData *) data { // the queue for all blocks here dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); // we want a dispatch_data_t referencing this NSData object // the logical thing is to have the dispatch cleanup block reference & release // the NSData, except we can't call -release on it under ARC. The solution is to // bridge-cast the NSData to a manually-counted CFDataRef, which we can release. CFDataRef cfData = CFBridgingRetain(data); dispatch_data_t ddata = dispatch_data_create(CFDataGetBytePtr(cfData), CFDataGetLength(cfData), q, ^{ CFRelease(cfData); }); dispatch_io_write(_io, 0, ddata, q, ^(bool done, dispatch_data_t d, int err) { if ( err != 0 ) { NSError * error = [NSError errorWithDomain: NSPOSIXErrorDomain code: err userInfo: nil]; NSLog(@"Failed to send data: %@", error); return; } else if ( done ) { NSLog(@"Sent %lu bytes of data", CFDataGetLength(cfData)); } }); } ``` 这里存在一个小问题，即需要将`NSData`对象转换为`dispatch_data`对象。由于在ARC下无法直接释放`NSData`对象，解决方法是使用免费桥接将`NSData`转换为手动管理的`CFData`对象，然后在清理块中手动释放它。 #### 2. 命令处理 `APAddressBookClient`对象解码后的命令会传递给其委托对象，通常是`APAddressBookBrowser`对象。在实现之前，需要在`APAddressBookBrowser.h`文件中添加相关协议声明： ```objc #import "APRemoteAddressBookInterface.h" #import "APAddressBookClient.h" @interface APRemoteAddressBookBrowser : NSObject <APRemoteAddressBookBrowser, APAddressBookClientDelegate, NSNetServiceBrowserDelegate, NSNetServiceDelegate> @end ``` 命令处理方法会提取命令的名称和UUID，根据这些信息向`_localAddressBook`实例发送相应的消息。以下是处理传入命令的代码示例： ```objc - (void) client: (APAddressBookClient *) client handleMessage: (NSDictionary *) command { void (^dataHandler)(NSArray *, NSError *) = ^(NSArray * values, NSError * error) { // ... }; NSString * name = command[APRemoteAddressBookCommandNameKey]; NSString * identifier = command[APRemoteAddressBookCommandPersonIDKey]; if ( [name isEqualToString: APRemoteAddressBookCommandAllPeople] ) { [_localAddressBook allPeople: dataHandler]; } else if ( [name isEqualToString: APRemoteAddressBookCommandGetMailingAddresses] ) { [_localAddressBook mailingAddressesForPersonWithIdentifier: identifier reply: dataHandler]; } else if ( [name isEqualToString: APRemoteAddressBookCommandGetEmailAddresses] ) { [_localAddressBook emailAddressesForPersonWithIdentifier: identifier reply: dataHandler]; } else if ( [name isEqualToString: APRemoteAddressBookCommandGetPhoneNumbers] ) { [_localAddressBook phoneNumbersForPersonWithIdentifier: identifier reply: dataHandler]; } else { id userInfo = @{ NSLocalizedDescriptionKey : @"Unknown command" }; NSError * error = [NSError errorWithDomain: APRemoteAddressBookErrorDomain code: 101 userInfo: userInfo]; dataHandler(nil, error); } } - (void) clientDisconnected: (APAddressBookClient *) client withError: (NSError *) error { // not doing anything with the error, which has already been logged. [_clients removeObject: client]; } ``` 数据处理程序会将结果打包为JSON数据，并发送回发送命令的客户端。以下是命令数据处理程序的代码： ```objc NSMutableDictionary * result = [NSMutableDictionary new]; NSUUID * uuid = command[APRemoteAddressBookCommandUUIDKey]; result[APRemoteAddressBookCommandNameKey] = APRemoteAddressBookCommandReply; result[APRemoteAddressBookCommandUUIDKey] = uuid; if ( values != nil ) result[APRemoteAddressBookCommandValueKey] = values; if ( error != nil ) result[APRemoteAddressBookCommandErrorKey] = [error jsonDictionaryRepresentation]; NSError * jsonError = nil; NSData * jsonData = [NSJSONSerialization dataWithJSONObject: result options: 0 error: &jsonError]; if ( jsonData == nil ) { NSLog(@"Error building JSON reply: %@. Message = %@. Reply = %@", jsonError, command, result); return; } // send the data asynchronously [client sendData: jsonData]; ``` #### 3. 访问远程地址簿 要访问网络上其他应用实例的地址簿，应用需要按以下三个步骤执行： - 向XPC服务代理对象发送`-availableServiceNames:`消息，获取可用服务列表，并在窗口中显示给用户。 - 用户选择服务后，应用向XPC代理发送`-attachToRemoteAddressBookWithName:handler:`消息以建立连接。 - 连接成功后，显示新的地址簿窗口，并通过向XPC代理发送`-allPeople:`消息异步加载人员列表。 以下是连接服务的方法实现： ```objc - (void) connectToServiceWithName: (NSString *) name replyHandler: (void (^)(id<APRemoteAddressBook>, NSError *)) replyHandler { NSLog(@"Connecting to service named '%@'", name); __block NSNetService * selected = nil; // search individual domains -- look in "local" domain first, then any others NSMutableArray * localServices = _servicesByDomain[@"local."]; NSLog(@"Searching local services: %@", localServices); for ( NSNetService * service in localServices ) { if ( [[service name] isEqualToString: name] ) { NSLog(@"Found local service: %@", service); selected = service; break; } } // if no local services were found, look in the other domains if ( selected == nil ) { [_servicesByDomain enumerateKeysAndObjectsUsingBlock: ^(id key, id obj, BOOL *stop) { if ( [key isEqualToString: @"local."] ) return; // skip local domain, we've already looked there NSLog(@"Searching services in domain '%@': %@", key, obj); for ( NSNetService * service in obj ) { if ( [[service name] isEqualToString: name] ) { NSLog(@"Found service: %@", service); selected = service; *stop = YES; break; } } }]; } // if none were found at all, send back an error if ( selected == nil ) { NSDictionary * info = @{ NSLocalizedDescriptionKey : NSLocalizedString(@"An address book service with the provided name could not be found.", @"error") }; ```