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一、CFBridgingRelease
Moves a non-Objective-C pointer to Objective-C and also transfers ownership to ARC.
把非OC的指针指向OC并且转换成ARC。
二、Declaration
id CFBridgingRelease(CFTypeRef X);
三、Discussion
You use this function to cast a Core Foundation-style object as an Objective-C object and transfer ownership of the object to ARC such that you don’t have to release the object, as illustrated in this example:
使用举例如下：
CFStringRef cfName = ABRecordCopyValue(person, kABPersonFirstNameProperty);
NSString *name = (NSString *)CFBridgingRelease(cfName);
四、相关CFBridgingRetain
Casts an Objective-C pointer to a Core Foundation pointer and also transfers ownership to the caller.
使用举例：
NSString *string = <#Get a string#>;
CFStringRef cfString = (CFStringRef)CFBridgingRetain(string);
// Use the CF string.
CFRelease(cfString);
五、实战使用
字符串分类，让字符串转url
/**
字符串转url
@return 由字符串转化成的NSURL
*/
- (NSURL *)url;
/**
字符串转url
@return 由字符串转化成的NSURL
*/
- (NSURL *)url {
return [NSURL URLWithString:(NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)self, (CFStringRef)@"!$&'()*+,-./:;=?@_~%#[]", NULL, kCFStringEncodingUTF8))];
}
六、附CFURLCreateStringByAddingPercentEscapes
Creates a copy of a string, replacing certain characters with the equivalent percent escape sequence based on the specified encoding.
创建一个字符串副本，代替并使用指定格式编码。
6.1 Declaration
定义：
CFStringRef CFURLCreateStringByAddingPercentEscapes(CFAllocatorRef allocator, CFStringRef originalString, CFStringRef charactersToLeaveUnescaped, CFStringRef legalURLCharactersToBeEscaped, CFStringEncoding encoding);
6.2 参数
- allocator
The allocator to use to allocate memory for the new CFString
object. Pass NULL
or kCFAllocatorDefault to use the current default allocator.
这个参数传NULL和kCFAllocatorDefault就行
- originalString
The CFString object to copy.
传一个CFString对象
- charactersToLeaveUnescaped
Characters whose percent escape sequences you want to leave intact. Pass NULL to specify that all illegal characters be escaped.
字符转义，传NULL指定所有非法字符转义。
如例所示，里面的字符在url中是非法的，需要转义。
- legalURLCharactersToBeEscaped
Legal characters to be escaped. Pass NULL to specify that no legal characters be replaced.
合法字符除外。传NULL指定不合法字符被替换。
- encoding
编码格式，毫无疑问的UTF8。
6.3 返回值
A copy of originalString replacing certain characters.
一份原始字符串取代了某些字符。
