Swift中的字符串文字-无法识别换行符\\ n

Question

I want to declare a string that contains my public RSA key. In Objective-C I did it like this:

NSString *pubKey = @"-----BEGIN RSA PUBLIC KEY-----\n"
  "MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu\n"
  "ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A\n"
  "+xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw\n"
  "mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN\n"
  "QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P\n"
  "+0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB\n"
  "-----END RSA PUBLIC KEY-----";

When I display this string in the debugger, it looks like this:

-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu
ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A
+xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw
mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN
QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P
+0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB
-----END RSA PUBLIC KEY-----

I am now trying to declare the exact same string in Swift (Xcode 10.2) and have not been able to get it to work.

What I tried was this:

let pubKeyArray : [String]
let pubKey : String

self.pubKeyArray = ["-----BEGIN RSA PUBLIC KEY-----",
  "MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu",
  "ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A",
  "+xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw",
  "mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN",
  "QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P",
  "+0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB",
  "-----END RSA PUBLIC KEY-----"]

self.pubKey = self.pubKeyArray.joined(separator: "\n")

When I display this string in the Debugger, it looks like this:

"-----BEGIN RSA PUBLIC KEY-----\nMIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu\nERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A\n+xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw\nmwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN\nQSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P\n+0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB\n-----END RSA PUBLIC KEY-----"

So basically, the new line character is not recognized. I also tried "\\\\n" and "\\r\\n", but to no avail.

What is the correct separator to use here?

Answer 1

The string you are seeing in the debugger is the debugDescription of the string. The debugDescription will replace things like the new line character with a backslash + n (It is supposed to make it clear that there is a new line).

If you want to see the actual string, you should just print it. In lldb , do:

po print(pubKey)

Answer 2

Rather than building an array and building a string from that, you can instead use a multi-line string literal. As The Swift Programming Language says:

Multiline String Literals

If you need a string that spans several lines, use a multiline string literal—a sequence of characters surrounded by three double quotation marks:

 let quotation = """ The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked. "Begin at the beginning," the King said gravely, "and go on till you come to the end; then stop." """ 

So, in your case:

let pubKey = """
    -----BEGIN RSA PUBLIC KEY-----
    MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu
    ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A
    +xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw
    mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN
    QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P
    +0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB
    -----END RSA PUBLIC KEY-----

    """

Note that blank line between “END RSA PUBLIC KEY” line and the closing quotes. That's because your original Objective-C example suggested that you wanted a newline at the end of that last line. If you don't need that last newline character, just omit that blank line at the end, eg:

let pubKey = """
    -----BEGIN RSA PUBLIC KEY-----
    MIIBCgKCAQEA+xGZ/wcz9ugFpP07Nspo6U17l0YhFiFpxxU4pTk3Lifz9R3zsIsu
    ERwta7+fWIfxOo208ett/jhskiVodSEt3QBGh4XBipyWopKwZ93HHaDVZAALi/2A
    +xTBtWdEo7XGUujKDvC2/aZKukfjpOiUI8AhLAfjmlcD/UZ1QPh0mHsglRNCmpCw
    mwSXA9VNmhz+PiB+Dml4WWnKW/VHo2ujTXxq7+efMU4H2fny3Se3KYOsFPFGZ1TN
    QSYlFuShWrHPtiLmUdPoP6CV2mML1tk+l7DIIqXrQhLUKDACeM5roMx0kLhUWB8P
    +0uj1CNlNN4JRZlC7xFfqiMbFRU9Z4N6YwIDAQAB
    -----END RSA PUBLIC KEY-----
    """

Now, when you display this in the debugger, you'll see the \\n characters represented there, but that's just an artifact of how the debugger represents non-visible characters. Rest assured that those are really newline characters.