swift中文文档翻译之--字符串和字符

字符串和字符

A string is an ordered collection of characters, such as "hello, world" or "albatross". Swift strings are represented by the String type, which in turn represents a collection of values of Character type.

Swift’s String and Character types provide a fast, Unicode-compliant way to work with text in your code. The syntax for string creation and manipulation is lightweight and readable, with a similar syntax to C strings. String concatenation is as simple as adding together two strings with the + operator, and string mutability is managed by choosing between a constant or a variable, just like any other value in Swift.

字符串是一串有序的字符集合，如“hello, world”或“albatross”。Swift 字符串是由String类型表示，这又代表字符类型的值的集合。

Swift的String 和Character 类型提供了一种快速，兼容Unicode的方式来在你的代码中与文本工作。字符串的创建和操作语法是简便和易读的 ，与C语言的字符串有着类似的语法。字符串连接很简单的，只要使用+运算符把两个字符串相加即可，字符串的可变性由常量或变量之间进行选择来管理，就像在Swift中任何的其他值。

Despite this simplicity of syntax, Swift’s String type is a fast, modern string implementation. Every string is composed of encoding-independent Unicode characters, and provides support for accessing those characters in various Unicode representations.

Strings can also be used to insert constants, variables, literals, and expressions into longer strings, in a process known as string interpolation. This makes it easy to create custom string values for display, storage, and printing.

Note

Swift’s String type is bridged seamlessly to Foundation’s NSString class. If you are working with the Foundation framework in Cocoa or Cocoa Touch, the entire NSString API is available to call on any String value you create, in addition to the String features described in this chapter. You can also use a String value with any API that requires an NSString instance.

For more information about using String with Foundation and Cocoa, see Using Swift with Cocoa and Objective-C.

String Literals

字符串字面值

You can include predefined String values within your code as string literals. A string literal is a fixed sequence of textual characters surrounded by a pair of double quotes ("").

A string literal can be used to provide an initial value for a constant or variable:在你的代码中你可以在字符串字面值中包含预定义的字符串值。字符串面值是由一对双引号括（“”）起来的文本字符的固定顺序。

字符串面值可以被用来提供一个常量或变量的初始值：

•     let someString = "Some string literal value"

Note that Swift infers a type of String for the someString constant, because it is initialized with a string literal value.

String literals can include the following special characters:

    The escaped special characters \0 (null character), \\ (backslash), \t (horizontal tab), \n (line feed), \r (carriage return), \" (double quote) and \' (single quote)

    Single-byte Unicode scalars, written as \xnn, where nn is two hexadecimal digits

    Two-byte Unicode scalars, written as \unnnn, where nnnn is four hexadecimal digits

    Four-byte Unicode scalars, written as \Unnnnnnnn, where nnnnnnnn is eight hexadecimal digits

The code below shows an example of each kind of special character. The wiseWords constant contains two escaped double quote characters. The dollarSign, blackHeart, and sparklingHeart constants demonstrate the three different Unicode scalar character formats:

    let wiseWords = "\"Imagination is more important than knowledge\" - Einstein"
    // "Imagination is more important than knowledge" - Einstein
    let dollarSign = "\x24" // $, Unicode scalar U+0024
    let blackHeart = "\u2665" // ♥, Unicode scalar U+2665
    let sparklingHeart = "\U0001F496" //