在Obj-C中,此代码用于将NSData转换为unsigned char：
unsigned char *dataToSentToPrinter = (unsigned char *)malloc(commandSize);
在Swift中,unsigned char被称为CUnsignedChar,但是如何在Swift中将NSData对象转换为CUnsignedChar？
解决方法
这可能是你正在寻找的：
let commandsToPrint: NSData = ... // Create char array with the required size: var dataToSentToPrinter = [CUnsignedChar](count: commandsToPrint.length,repeatedValue: 0) // Fill with bytes from NSData object: commandsToPrint.getBytes(&dataToSentToPrinter,length: sizeofValue(dataToSentToPrinter))
更新：实际上你根本不需要复制数据(两者都没有)
Objective-C代码也不在Swift中).有一个指向数据的指针就足够了.
所以你的代码看起来像这样(比较
Error (“‘()’ is not identical to ‘UInt8′”) writing NSData bytes to NSOutputStream using the write function in Swift
对于类似的问题)：
let dataToSentToPrinter = UnsafePointer<CUnsignedChar>(commandsToPrint.bytes)
let commandSize = commandsToPrint.length
var totalAmountWritten = 0
while totalAmountWritten < commandSize {
let remaining = commandSize - totalAmountWritten
let amountWritten = starPort.writePort(dataToSentToPrinter,totalAmountWritten,remaining)
totalAmountWritten += amountWritten
// ...
}
