Swift 字符串初始值设定项？

Question

我在一本 Swift 教学书中看到了这两个语句。

1. let padding = String(count: spaces, repeatedValue: Character(""))
2. println(String(format:"%@%@", "Year", "Test"))

我的问题是:

1. 都是 String(count:repeatedValue:) 和 String(format:) 的初始化器
   字符串？
2. 我找不到 String(format:) 的联机文档你能推荐任何链接吗？
3. 还有哪些可用的 String 初始值设定项？我只能找到 init()和 Apple 文档中的 init(count:repeatedValue)

非常感谢。

Answer 1

String 是 Swift 中的结构体。您可以在 Xcode 本身中获取文档。

下面是详细信息。

/// Objective-C Bridge /// ================== /// /// String is bridged to Objective-C as NSString, and a String /// that originated in Objective-C may store its characters in an /// NSString. Since any arbitrary subclass of NSSString can /// become a String, there are no guarantees about representation or /// efficiency in this case. Since NSString is immutable, it is /// just as though the storage was shared by some copy: the first in /// any sequence of mutating operations causes elements to be copied /// into unique, contiguous storage which may cost O(N) time and /// space, where N is the length of the string representation (or /// more, if the underlying NSString is has unusual performance /// characteristics).

struct String {
    init()
}

这里是字符串的扩展。

extension String {

    /// Construct an instance that is the concatenation of `sz` copies
    /// of `repeatedValue`
    init(count sz: Int, repeatedValue c: Character)

    /// Construct an instance that is the concatenation of `sz` copies
    /// of `Character(repeatedValue)`
    init(count: Int, repeatedValue c: UnicodeScalar)

    /// `true` iff `self` contains no characters.
    var isEmpty: Bool { get }
}