不推荐使用CFURLCreateDataAndPropertiesFromResource。并寻找替代品

Question

除了Apple的Load Preset演示示例代码中包含的许多其他内容之外，现在不推荐调用CFURLCreateDataAndPropertiesFromResource。但是我无法找到它的替代品 - 无论是选项点击还是看看参考资料都告诉我的不仅仅是它不再是完成的事情。

CFDataRef propertyResourceData = 0;
Boolean status;
SInt32 errorCode = 0;
OSStatus result = noErr;

// Read from the URL and convert into a CFData chunk
status = CFURLCreateDataAndPropertiesFromResource (
                                                   kCFAllocatorDefault,
                                                   (__bridge CFURLRef) presetURL,
                                                   &propertyResourceData,
                                                   NULL,
                                                   NULL,
                                                   &errorCode
                                                   );


NSAssert (status == YES && propertyResourceData != 0, @"Unable to create data and properties from a preset. Error code: %d '%.4s'", (int) errorCode, (const char *)&errorCode);

// Convert the data object into a property list
CFPropertyListRef presetPropertyList = 0;
CFPropertyListFormat dataFormat = 0;
CFErrorRef errorRef = 0;
presetPropertyList = CFPropertyListCreateWithData (
                                                   kCFAllocatorDefault,
                                                   propertyResourceData,
                                                   kCFPropertyListImmutable,
                                                   &dataFormat,
                                                   &errorRef
                                                   );

// Set the class info property for the Sampler unit using the property list as the value.
if (presetPropertyList != 0) {

    result = AudioUnitSetProperty(
                                  self.samplerUnit,
                                  kAudioUnitProperty_ClassInfo,
                                  kAudioUnitScope_Global,
                                  0,
                                  &presetPropertyList,
                                  sizeof(CFPropertyListRef)
                                  );

    CFRelease(presetPropertyList);
}

if (errorRef) CFRelease(errorRef);
CFRelease (propertyResourceData);

return result;

Answer 1

对于属性： CFURLCopyResourcePropertiesForKeys示例属性：kCFURLFileSizeKey和kCFURLContentModificationDateKey，或基础样式[NSURL resourceValuesForKeys:error:]。

对于数据： +[NSData dataWithContentsOfURL:options:error:]。

他们没有被记录为替代品，AFAIK。大多数这些新的替代API已经存在了几年。

修改

在您在编辑中发布的这个示例中，程序没有请求属性，因此您只需要URL presetURL处的数据。

您可以通过以下方式实现这一目标：

NSURL * presetURL = ...;
// do review these options for your needs. you can make great
// optimizations if you use memory mapping or avoid unnecessary caching.
const NSDataReadingOptions DataReadingOptions = 0;
NSError * outError = nil;
NSData * data = [NSData dataWithContentsOfURL:presetURL
                                      options:DataReadingOptions
                                        error:&outError];

const bool status = nil != data; // << your `status` variable

if (!status) {
 // oops - an error was encountered getting the data see `outError`
}
else {
 // use the data
}

Answer 2

我发现只使用以下内容即可删除更多代码：

OSStatus result = noErr;
NSData* data = [NSData dataWithContentsOfURL:presetURL];
id propertyList = [NSPropertyListSerialization propertyListWithData:data options:NSPropertyListImmutable format:NULL error:NULL];

// Set the class info property for the Sampler unit using the property list as the value.
if (propertyList) {
    result = AudioUnitSetProperty(
                                  self.samplerUnit,
                                  kAudioUnitProperty_ClassInfo,
                                  kAudioUnitScope_Global,
                                  0,
                                  (__bridge CFPropertyListRef)propertyList,
                                  sizeof(CFPropertyListRef)
                                  );
}

return result;

Answer 3

我最终使用了此代码https://developer.apple.com/library/mac/technotes/tn2283/_index.html#//apple_ref/doc/uid/DTS40011217-CH1-TNTAG2

- (OSStatus) loadSynthFromPresetURL: (NSURL *) presetURL {

OSStatus result = noErr;

AUSamplerInstrumentData auPreset = {0};

auPreset.fileURL = (__bridge CFURLRef) presetURL;
auPreset.instrumentType = kInstrumentType_AUPreset;

result = AudioUnitSetProperty(self.samplerUnit,
                              kAUSamplerProperty_LoadInstrument,
                              kAudioUnitScope_Global,
                              0,
                              &auPreset,
                              sizeof(auPreset));

return result;