Swift 提供了三種方式來比較字符串的值：字符串相等、前綴相等和后綴相等。
如果兩個字符串以同一順序包含完全相同的字符，則認(rèn)為兩者字符串相等：
let quotation = "我們是一樣一樣滴."
let sameQuotation = "我們是一樣一樣滴."
if quotation == sameQuotation {
println("這兩個字符串被認(rèn)為是相同的")
}
// 打印輸出："這兩個字符串被認(rèn)為是相同的"
通過調(diào)用字符串的hasPrefix/hasSuffix方法來檢查字符串是否擁有特定前綴/后綴。 兩個方法均需要以字符串作為參數(shù)傳入并傳出Boolean值。 兩個方法均執(zhí)行基本字符串和前綴/后綴字符串之間逐個字符的比較操作。
下面的例子以一個字符串?dāng)?shù)組表示莎士比亞話劇《羅密歐與朱麗葉》中前兩場的場景位置：
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"
]
您可以利用hasPrefix方法來計算話劇中第一幕的場景數(shù)：
var act1SceneCount = 0
for scene in romeoAndJuliet {
if scene.hasPrefix("Act 1 ") {
++act1SceneCount
}
}
println("There are \(act1SceneCount) scenes in Act 1")
// 打印輸出："There are 5 scenes in Act 1"
相似地，您可以用hasSuffix方法來計算發(fā)生在不同地方的場景數(shù)：
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
}
}
println("\(mansionCount) mansion scenes; \(cellCount) cell scenes")
// 打印輸出："6 mansion scenes; 2 cell scenes”
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