如何正确释放CF对象？

Question

我有这种方法(别人写了!)

- (CGPDFDocumentRef)getPdf {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];

    NSString *pdfPath = [documentsDirectory stringByAppendingPathComponent:@"myLocalFileName.pdf"];

    NSURL *pdfURL = [NSURL fileURLWithPath:pdfPath];

    CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);

    return pdf;
}

现在,我运行了Analyze并获得三个内存泄漏警告:

Call to function 'CGPDFDocumentCreateWithURL' returns a Core Foundation object with a +1 retain count
Object returned to caller as an owning reference (single retain count transferred to caller)
Object leaked: object allocated and stored into 'pdf' is returned from a method whose name ('getPdf') does not start with 'copy', 'mutableCopy', 'alloc' or 'new'.  This violates the naming convention rules given in the Memory Management Guide for Cocoa

有人可以告诉我这里需要/应该做些什么？我知道我应该在CF函数名称中创建或复制CFRelease所有内容.我不明白的是我如何发布pdf并仍能在函数结束时返回它.我错过了什么？谢谢.

Answer 1

您需要clang源注释,如此处所示http://cocoasamurai.blogspot.com/2012/01/clang-source-annotations.html

    #import <AppKit/AppKit.h>
@interface NSColor (CWNSColorAdditions)
-(CGColorRef)cw_cgColor CF_RETURNS_RETAINED;
@end

Answer 2

收到pdf的代码有责任在完成后将其发送给CFRelease.与Cocoa不同,CF不支持自动释放,因此从CF函数返回的任何对象都是调用者拥有并必须处理的对象.

它也是命名约定,那些返回CF对象的函数应该用create或者相应地命名copy