swift - Xcode 8 beta 6 中的 MusicEventIteratorGetEventInfo

Question

直到 Xcode 8 beta 5，我可以在 MusicEventIterator 中访问事件信息，使用类似:

var type: MusicEventType = 0
var stamp: MusicTimeStamp = 0
var data: UnsafePointer<()>? = nil
var size: UInt32 = 0

while(hasCurrentEvent != false) {
        MusicEventIteratorGetEventInfo(iterator!, &stamp, &type,
        &data, &size) 
    // do stuff with stamp, type, data...
}

我设法在 Apple 开发站点上获得了一些关于处理“数据”的帮助，但是首先获取数据也被破坏了。我收到有关在“数据”声明中使用“UnsafeRawPointer”的警告，以及有关无法在调用 MusicEventIteratorGetEventInfo() 时将数据用作 inout 参数的错误...虽然我知道他们正在使事情变得更具确定性和面向 future (即，对于编译器)，但每隔几个月 C-interop 的东西就发生变化是非常令人沮丧的。我的 MIDI 文件解析器代码已经更改了 3 次...

作为引用，MusicEventIteratorGetEventInfo 具有签名:

func MusicEventIteratorGetEventInfo(_ inIterator: MusicEventIterator,
 _ outTimeStamp: UnsafeMutablePointer<MusicTimeStamp>,
 _ outEventType: UnsafeMutablePointer<MusicEventType>,
 _ outEventData: UnsafeMutablePointer<UnsafePointer<Void>>,
 _ outEventDataSize: UnsafeMutablePointer<UInt32>) -> OSStatus

非常感谢任何帮助。

Answer 1

latest reference of MusicEventIteratorGetEventInfo 显示这个:

Declaration

func MusicEventIteratorGetEventInfo(_ inIterator: MusicEventIterator, 
                                  _ outTimeStamp: UnsafeMutablePointer<MusicTimeStamp>, 
                                  _ outEventType: UnsafeMutablePointer<MusicEventType>, 
                                  _ outEventData: UnsafeMutablePointer<UnsafeRawPointer?>, 
                                  _ outEventDataSize: UnsafeMutablePointer<UInt32>) -> OSStatus

第三个参数outEventData类型为 UnsafeMutablePointer<UnsafeRawPointer?> .通常，当 API 声明 UnsafeMutablePointer<T> 时, 你声明了一个 T 类型的变量，并将其作为 inout 参数传递。

所以，这应该可行:

var type: MusicEventType = 0
var stamp: MusicTimeStamp = 0
var data: UnsafeRawPointer? = nil //<- Declare a variable of type `UnsafeRawPointer?`.
var size: UInt32 = 0

while hasCurrentEvent != false {
    MusicEventIteratorGetEventInfo(iterator!, &stamp, &type,
                                   &data, &size) //<- Pass it as an inout argument.
    // do stuff with stamp, type, data...
}