swift输入输出

/// Returns a string read from standard input through the end of the current
/// line or until EOF is reached.
///
/// Standard input is interpreted as `UTF-8`. Invalid bytes are replaced by
/// Unicode [replacement characters][rc].
///
/// [rc]:
/// https://unicode.org/glossary/#replacement_character
///  Replacement Character: A character used as a substitute for an uninterpretable character from another encoding. The Unicode Standard uses U+FFFD replacement character for this function.
/// - Parameter strippingNewline: If `true`, newline characters and character
///   combinations are stripped from the result; otherwise, newline characters
///   or character combinations are preserved. The default is `true`.
/// - Returns: The string of characters read from standard input. If EOF has
///   already been reached when `readLine()` is called, the result is `nil`.
public func readLine(strippingNewline: Bool = true) -> String?

1,读取字符串
if let input = readLine(){
    print(input)
}

2,读取数值
if let input = readLine() {
    if let floatValue = Float(input) {
        print("floatValue: \(floatValue)")
    }
}

3,多次连续读取
var inputArray :[String]
while let input = readLine() {
    guard input != "quit" else {
        break
    }
    inputArray.append(input)
}

4,读取通过特殊字符分割字符串数组
let inputArray = readLine()?.split(separator: " ")

/// Writes the textual representations of the given items into the standard
/// output.
///
/// You can pass zero or more items to the `print(_:separator:terminator:)`
/// function. The textual representation for each item is the same as that
/// obtained by calling `String(item)`. The following example prints a string,
/// a closed range of integers, and a group of floating-point values to
/// standard output:
///
///     print("One two three four five")
///     // Prints "One two three four five"
///
///     print(1...5)
///     // Prints "1...5"
///
///     print(1.0, 2.0, 3.0, 4.0, 5.0)
///     // Prints "1.0 2.0 3.0 4.0 5.0"
///
/// To print the items separated by something other than a space, pass a string
/// as `separator`.
///
///     print(1.0, 2.0, 3.0, 4.0, 5.0, separator: " ... ")
///     // Prints "1.0 ... 2.0 ... 3.0 ... 4.0 ... 5.0"
///
/// The output from each call to `print(_:separator:terminator:)` includes a
/// newline by default. To print the items without a trailing newline, pass an
/// empty string as `terminator`.
///
///     for n in 1...5 {
///         print(n, terminator: "")
///     }
///     // Prints "12345"
///
/// - Parameters:
///   - items: Zero or more items to print.
///   - separator: A string to print between each item. The default is a single
///     space (`" "`).
///   - terminator: The string to print after all items have been printed. The
///     default is a newline (`"\n"`).
public func print(_ items: Any..., separator: String = " ", terminator: String = "\n")