DAY3:String & Character

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哈哈哈，刚才看见微博，有人推荐一个神奇的工具，推荐给大家http://swiftlang.ng.bluemix.net/#/repl是IBM公司出的，编译器的版本是Swift2.2,现在可以使用之前的String的那些方法了，哈哈哈

插入和删除（Inserting and Removing）

调用insert(_:atIndex:)方法可以在一个字符串的指定索引插入一个字符

    var welcome = "hello"
    welcome.insert("!",atIndex:welcome.endIndex)
  //welcome现在就是"hello!"

还可以在一个字符串的指定索引插入一个字符串,调用insertContentsOf(_:at:)方法

welcome.insertContentsOf(" there".characters, at: welcome.endIndex.predecessor())
现在welcome就是"hello there!"(是接着上面的例子哦，暂时的编译器还是会报错的，待升级之后再试试)

调用removeAtIndex(_:) 方法可以在一个字符串的指定索引删除一个字符

var welcome = "hello there!"
welcome.removeAtIndex(welcome.endIndex.predecessor())
//这时候welcome的值就是"hello there"，把最后一个字符后一位的前一位移除了就是移除了"!"

调用removeRange(_:)方法可以在一个字符串指定索引删除一个子字符串

var welcome = "hello there"
let range = welcome.endIndex.advanceBy(-6)..

DAY2里面说过，我们可以调用advanceBy()来获取一个索引，编译器的原因暂时不能实现，上面的例子表示的意思是从空格删除到最后的e，welcome现在就等于hello

比较字符串(Comparing Strings)

let quotation = "We're a lot alike, you and I."
let sameQuotation = "We're a lot alike, you and I."
if quotation == sameQuotation {
    print("These two string are considered equal")
}
//These two string are considered equal

我们可以使用(==)和(!=)来比较，如果两个字符串的可扩展的字形群集是标准相等的，那么它们就是相等的，即使可扩展的字形群集是由不同的Unicode标量构成的，只要语言意义和外观相同就认为是相同的.

let a = "caf\u{E9}" //é
let b = "caf\u{65}\u{301}"  //e和重音符号
if a == b{
    print("These two strings are considered equal")
}
//These two strings are considered equal

前缀/后缀相等(Prefix and Suffix Equality )

通过调用字符串hasPrefix()/hasSuffix()方法来检查是否有前后缀，两个都输入一个String类型的参数，返回一个布尔值。这里举了一个例子，用一个定义为常量的数组romeoAndJuliet，可以看见，数组是用[]来申明的，数组内的变量用逗号隔开，具体的数据类型我看后面有详细的章节会讲，到时候学习

let romeoAndJuliet = [
"Act 1 Scene 1: Verona, A public place",
"Act 1 Scene 2: Capulet's mansion",
"Act 1 Scene 3: A room in Capulet's mansion",
"Act 1 Scene 4: A street outside Capulet's mansion",
"Act 1 Scene 5: The Great Hall in Capulet's mansion",
"Act 2 Scene 1: Outside Capulet's mansion",
"Act 2 Scene 2: Capulet's orchard",
"Act 2 Scene 3: Outside Friar Lawrence's cell",
"Act 2 Scene 4: A street in Verona",
"Act 2 Scene 5: Capulet's mansion",
"Act 2 Scene 6: Friar Lawrence's cell"
]

定义了一个变量用来计数前缀中含有Act 1的，这里一共有五次

var act1SceneCount = 0
for scene in romeoAndJuliet {
if scene.hasPrefix("Act 1"){
    ++act1SceneCount
  }
}
print("There are \(act1SceneCount) scenes in Act 1")
//There are 5 scenes in Act 1

定义了两个变量，来数字符串后缀中含有这两个的值,这里有一个for循环一个if，else if循环，具体的语法后面也有详细的章节讲解

var mansionCount = 0
var cellCount = 0
for scene in romeoAndJuliet{
if scene.hasSuffix("Capulet's mansion"){
    ++mansionCount
}else if scene.hasSuffix("Friar Lawrence's cell"){
    ++cellCount
  }
}
print("\(mansionCount) mansion scenes;\(cellCount) cell scenes")
//6 mansion scenes;2 cell scenes

Unicode Representations of Strings

apple的String&Character中还有这个章节Unicode Representations of Strings，这里就不示范了，有兴趣的大家可以看一下，我睡觉前看下～