在Swift中使用CFReadStreamCreateWithFTPURL测试FTP连接 [英] Test FTP connection using CFReadStreamCreateWithFTPURL in Swift

问题描述

  func OpenAndTestFTPConn（user：NSString，pass： NSString） - > Bool {
 
 var ftpstring =ftp：// \（user）：\（pass）@ \（txtTarget.stringValue）
 var ftpNSURL = NSURL（string：ftpstring ）
 var FTPStream = CFReadStreamCreateWithFTPURL（nil，ftpNSURL）
 var status：Bool 
 var cfstatus：Boolean = CFReadStreamOpen（FTPStream）as Boolean b $ b if cfstatus == 0 {
 status = false 
} 
 else {
 status = true 
} 
 println（status）
返回状态
 
} 
  

当我尝试构建它时，行 var cfstatus：Boolean = CFReadStreamOpen（ FTPStream）as Boolean 返回错误无法将表达式的类型'Boolean'转换为类型'CFReadStream！'。如果我删除了表达式两边的类型声明，则返回的错误是无法将表达式的类型'Boolean'转换为键入'$ T3'。

我在哪里出错？

注意： cstatus 定义和声明基于这篇文章。
CFReadStreamCreateWithFTPURL 方法返回一个非托管< CFReadStream> 此内容中的非托管对象部分Swift书。

对我来说，这段代码不会编译超过 CFReadStreamCreateWithFTPURL 因此而致电。我看不到布尔错误;奇怪的是，您在 CFReadStreamCreateWithFTPURL 调用中看到该错误并且没有错误。你在Beta3上吗？

我可以用以下代码编译代码：

  let FTPStream = CFReadStreamCreateWithFTPURL（nil，ftpNSURL）.takeRetainedValue（）
  

通过声明该函数已经保留了该值（再次，根据它的文档），将一个非托管值添加到兼容ARC的指针中。

顺便说一句，这是一个挑剔的问题，但所有您的 var 的可以是 let 的。

I am using the following code to try to test an FTP connection:

func OpenAndTestFTPConn(user:NSString, pass:NSString) -> Bool {

    var ftpstring = "ftp://\(user):\(pass)@\(txtTarget.stringValue)"
    var ftpNSURL = NSURL(string: ftpstring)
    var FTPStream = CFReadStreamCreateWithFTPURL(nil, ftpNSURL)
    var status:Bool
    var cfstatus:Boolean = CFReadStreamOpen(FTPStream) as Boolean
    if cfstatus == 0 {
        status = false
    }
    else {
        status = true
    }
    println(status)
    return status

}

When I try building this, the line var cfstatus:Boolean = CFReadStreamOpen(FTPStream) as Boolean returns the error Cannot convert the expression's type 'Boolean' to type 'CFReadStream!'. If I remove the type declarations on both sides of the expression, the error returned is Cannot convert the expression's type 'Boolean' to type '$T3'.

Where am I going wrong?

Note: the cstatus definition and statements are based on this post.

解决方案

The CFReadStreamCreateWithFTPURL method returns an Unmanaged<CFReadStream> (per the docs), meaning that this particular function doesn't yet have Swift-compatible annotations indicating whether returned values have been retained or not. For more details, see "Unmanaged Objects" in this section of the Swift book.

For me, this code doesn't compile past the CFReadStreamCreateWithFTPURL call because of this issue. I don't see the Boolean error; it's strange that you're seeing that error and no error on the CFReadStreamCreateWithFTPURL call. Are you on Beta3?

I was able to get the code to compile with:

let FTPStream = CFReadStreamCreateWithFTPURL(nil, ftpNSURL).takeRetainedValue()

which converts the unmanaged value to an ARC-compatible pointer by asserting that the function has already retained the value (again, per its docs).

BTW, it's a nitpick, but all of your var's can be let's.

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