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Toll-Free Bridging 对象桥接(Xcode文档翻译)

译者序:

带学生看Xcode API 文档的时候,总有学生被通篇的英文搞晕,并询问是否有中文版。

初步搜索和询问的结果是,中文版有但是很少。(如果知道哪里有,希望能够分享一下这个信息)

于是决心从今天开始对Xcode API进行翻译,这次的主题是"Toll-Free Bridging"。

英文原版版权归苹果公司所有,翻译内容仅供学习参考。

首发网址:http://blog.csdn.net/duzixi/article/details/38325021

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Toll-Free Bridging

对象桥接

There are a number of data types in the Core Foundation framework and the Foundation framework that can be used interchangeably. This capability, called toll-free bridging, means that you can use the same data type as the parameter to a Core Foundation function call or as the receiver of an Objective-C message. For example,NSLocale (see NSLocale Class Reference) is interchangeable with its Core Foundation counterpart, CFLocale (see CFLocale Reference). Therefore, in a method where you see anNSLocale * parameter, you can pass aCFLocaleRef, and in a function where you see aCFLocaleRef parameter, you can pass anNSLocale instance. You cast one type to the other to suppress compiler warnings, as illustrated in the following example.

Core Foundation框架和Foundation框架中有大量的数据类型能被可交换的使用。这个能力被称之为“对象桥接”,这就意味着你可以使用相同的数据类型作为Core Foudation函数调用的参数或者Objective-C消息的接受者。例如,NSLocale(参见NSLocale Class Reference)和它Core Foundation对应者CFLocale(参见 CFLocale Reference)是可交换的。因此,如果你在方法中看到了NSLocale *类型的参数,你就可以传入一个NSLocale对象。你通过传入一个类型到另一个去阻止编译警告,代码如下:

NSLocale *gbNSLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_GB"];


CFLocaleRef gbCFLocale = (CFLocaleRef) gbNSLocale;


CFStringRef cfIdentifier = CFLocaleGetIdentifier (gbCFLocale);


NSLog(@"cfIdentifier: %@", (NSString *)cfIdentifier);


// logs: "cfIdentifier: en_GB"


CFRelease((CFLocaleRef) gbNSLocale);


 


CFLocaleRef myCFLocale = CFLocaleCopyCurrent();


NSLocale * myNSLocale = (NSLocale *) myCFLocale;


[myNSLocale autorelease];


NSString *nsIdentifier = [myNSLocale localeIdentifier];


CFShow((CFStringRef) [@"nsIdentifier: " stringByAppendingString:nsIdentifier]);


// logs identifier for current locale


Note from the example that the memory management functions and methods are also interchangeable—you can useCFRelease with a Cocoa object andrelease andautorelease with a Core Foundation object.

值得注意的是,内存管理函数和方法也可交换的——你可以让Cocoa对象去使用CFRelease函数并且让Core Foundation对象去使用release和autorelease方法。

Note: When using garbage collection, there are important differences to how memory management works for Cocoa objects and Core Foundation objects. See “Using Core Foundation with Garbage Collection” for details.


注意:当使用垃圾回收机制时,Cocao对象和Core Foundation对象的内存管理有很大的不同。详细请参见“Using Core Foundation with Garbage Collection”。


Toll-free bridging has been available since OS X v10.0. Table 13-1 provides a list of the data types that are interchangeable between Core Foundation and Foundation. For each pair, the table also lists the version of OS X in which toll-free bridging between them became available.

对象桥接从OS X v10.0版本开始可用。表格 13 - 1 提供了能在Core Fundation框架和Foundation框架之间交换使用的数据类型列表。对于每一对,表格也列出了 OS X中对象桥接可用的版本信息。

Table 13-1  Data types that can be used interchangeably between Core Foundation and Foundation

表格 13-1 能够在Core Foundation框架和Foundation框架之间交换使用的数据对象

Core Foundation type        Foundation class               Availability  

Core Foundation类型          Foundation类(基础类)     可用版本

CFArrayRef                        NSArray                            OS X v10.0

CFAttributedStringRef   NSAttributedString       OS X v10.4

CFCalendarRef                  NSCalendar                       OS X v10.4

CFCharacterSetRef           NSCharacterSet               OS X v10.0

CFDataRef                          NSData                              OS X v10.0

CFDateRef                          NSDate                              OS X v10.0

CFDictionaryRef               NSDictionary                  OS X v10.0

CFErrorRef                         NSError                           OS X v10.5

CFLocaleRef                      NSLocale                          OS X v10.4

CFMutableArrayRef           NSMutableArray              OS X v10.0

CFMutableAttributedStringRef NSMutableAttributedStringOS X v10.4

CFMutableCharacterSetRefNSMutableCharacterSet OS X v10.0

CFMutableDataRef              NSMutableData               OS X v10.0

CFMutableDictionaryRef   NSMutableDictionary   OS X v10.0

CFMutableSetRef                NSMutableSet                 OS X v10.0

CFMutableStringRef          NSMutableString           OS X v10.0

CFNumberRef                        NSNumber                        OS X v10.0

CFReadStreamRef                NSInputStream               OS X v10.0

CFRunLoopTimerRef            NSTimer                           OS X v10.0

CFSetRef                             NSSet                               OS X v10.0

CFStringRef                       NSString                        OS X v10.0

CFTimeZoneRef                   NSTimeZone                     OS X v10.0

CFURLRef                             NSURL                              OS X v10.0

CFWriteStreamRef             NSOutputStream              OS X v10.0


Note: Not all data types are toll-free bridged, even though their names might suggest that they are. For example,NSRunLoop is not toll-free bridged to CFRunLoop,NSBundle is not toll-free bridged to CFBundle, andNSDateFormatter is not toll-free bridged to CFDateFormatter.


注意:并不是所有的类型都是对象桥接,尽管其名称让它们看上去很像。例如,NSRunLoop和CFRunLoop不能对象桥接,NSBundle和CFBundle不能对象桥接,NSDateFormatter和CFDateFormatter不能对象桥接等。


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