ARC的正确桥接? [英] Correct bridging for ARC?

问题描述

我有一个NSString的类别类.

@implementation NSString (URLEncode)

- (NSString *)URLEncodedString
{
    __autoreleasing NSString *encodedString;

    NSString *originalString = (NSString *)self;    
    encodedString = (__bridge_transfer NSString * )
            CFURLCreateStringByAddingPercentEscapes(NULL,
                                (__bridge CFStringRef)originalString,
                                NULL,
                                (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                kCFStringEncodingUTF8);
    return encodedString;
}

我是否为ARC和新的LLVM使用正确的网桥传输?

原始代码:

- (NSString *)URLEncodedString
    NSString *encodedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL,
                                (CFStringRef)self,
                                NULL,
                                (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                kCFStringEncodingUTF8);
    return [encodedString autorelease];
}

解决方案

如评论中所述，我认为谈论ARC和 4.3.4通过写回传递给out参数. /p>

根据 3.2.4桥接演员表，__bridge_transfer是正确的，因为CFURLCreateStringByAddingPercentEscapes函数返回保留的对象(其名称中具有"create").您希望ARC拥有返回对象的所有权，并插入一个发行版(在这种情况下为自动发行版)来平衡这一点.

originalstring的__bridge强制转换也是正确的，您不希望ARC对它做任何特殊的事情.

I have a category class for NSString.

@implementation NSString (URLEncode)

- (NSString *)URLEncodedString
{
    __autoreleasing NSString *encodedString;

    NSString *originalString = (NSString *)self;    
    encodedString = (__bridge_transfer NSString * )
            CFURLCreateStringByAddingPercentEscapes(NULL,
                                (__bridge CFStringRef)originalString,
                                NULL,
                                (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                kCFStringEncodingUTF8);
    return encodedString;
}

Am I using the correct bridge transfers for ARC and the new LLVM?

The original code:

- (NSString *)URLEncodedString
    NSString *encodedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL,
                                (CFStringRef)self,
                                NULL,
                                (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                kCFStringEncodingUTF8);
    return [encodedString autorelease];
}

解决方案

As mentioned in the comments, I think it's fine to talk about ARC and the contents of Automatic Reference Counting here.

__autoreleasing is not meant to be used like that. It's used for passing indirect object references (NSError**, etc). See 4.3.4 Passing to an out parameter by writeback.

According to 3.2.4 Bridged casts, the __bridge_transfer is correct as the CFURLCreateStringByAddingPercentEscapes function returns a retained object (it has "create" in its name). You want ARC to take ownership of the returned object and insert a release (or autorelease in this case) to balance this out.

The __bridge cast for originalstring is correct too, you don't want ARC to do anything special about it.

这篇关于ARC的正确桥接?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！