小编典典

使用Swift中的写入功能将NSData字节写入NSOutputStream时出错(“(')'与'UInt8'”不同)

swift

我正在尝试基于Erica
Sadun的方法
在Swift中构建异步文件下载。但是我需要它来处理更大的文件,因此我找到了有关使用NSOutputStream而不是NSData的答案,这是有意义的。

但是,我无法使其正常工作。当我尝试将NSData字节(在我的NSURLConnection
didReceiveData函数中)添加到NSOutputStream写入函数时,出现以下错误:'()' is not identical to 'UInt8'在该行:bytesWritten = self.downloadStream.write(data.bytes, maxLength: bytesLeftToWrite)

data.bytes是类型ConstUnsafePointer<()>.write()函数期望类型是ConstUnsafePointer<UInt8>,因此从这个意义上说,错误是完全合理的。但是由于我是iOS的新手,当然还不熟悉Swift编程,所以我不了解如何解决此问题。

因此,如何将转换data.bytes: ConstUnsafePointer<()>ConstUnsafePointer<UInt8>alt。以其他方式进行这项工作?

我的didReceiveData功能:

func connection(connection: NSURLConnection!, didReceiveData data: NSData!) {

    var bytesLeftToWrite: NSInteger = data.length
    var bytesWritten: NSInteger = 0

    while bytesLeftToWrite > 0 {

        bytesWritten = self.downloadStream.write(data.bytes, maxLength: bytesLeftToWrite)

        if bytesWritten == -1 {

            break

        }

        bytesLeftToWrite -= bytesWritten

        let responseExpectedlenght: NSNumber = NSNumber(longLong: self.downloadResponse!.expectedContentLength)
        let dataLength: NSNumber = NSNumber(long: data.length)

        self.downloadProgressPercentage = ((dataLength / responseExpectedlenght) * 100)

        println("Downloaded: \(self.downloadProgressPercentage)%")

    }

}

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2020-07-07

共1个答案

小编典典

您可以使用以下方法转换指针UnsafePointer()

bytesWritten = self.downloadStream.write(UnsafePointer(data.bytes), maxLength: bytesLeftToWrite)

在写循环中还有一个问题,因为您总是将数据对象的 初始 字节写入 输出流。

它可能看起来与此类似(未试用):

var bytes = UnsafePointer<UInt8>(data.bytes)
var bytesLeftToWrite: NSInteger = data.length

while bytesLeftToWrite > 0 {
    let bytesWritten = self.downloadStream.write(bytes, maxLength: bytesLeftToWrite)
    if bytesWritten == -1 {
        break // Some error occurred ...
    }

    bytesLeftToWrite -= bytesWritten
    bytes += bytesWritten // advance pointer

    // ...
}
2020-07-07