无法在Swift中将NSData标头与字符串进行比较

Question

I am trying to compare the header (first bytes of NSData) against a string, I can successfully print the string, but comparing doesn't work.

This is what I've tried:

var dataHeader:NSString = NSString(bytes: data.bytes, length: min(data.length, 8), encoding: NSASCIIStringEncoding)!

println(dataHeader)
result: PK

The ASCII of "PK" is 0x50 0x4B.

When I try the following, nothing happens:

if dataHeader == "PK" {

}

Maybe I'm a noob but I don't have any ideas left, so does anyone have an idea on how to solve this? I am guessing it has something to do with the string encoding, but after doing a lot of research, I still can't figure it out.

Any help is appreciated, thanks!

Answer 1

Is it possible there are other non-printing characters after the "PK" if this is binary data? What's the length of the string dataHeader ?

If there are other funny characters after, you can truncate the string or use NSString's hasPrefix: method:

if dataHeader.hasPrefix("PK") {
  // do something
}