Question

我有一个字符串：

let s : String = "The dog ate the cat."

使用以下模式：

let p : NSRegularExpression = try! NSRegularExpression(pattern: "\\w( )?dog( )?\\w"), options: .CaseInsensitive)

我的问题是：如何在模式出现之前和之后得到单词？

这是我目前的实施：

let t : [NSTextCheckingResults] = p.matchesInString(s, options: [], NSMakeRange(0, NSString(string: s).length))
print(String(t[0].URL!))

然而，这不会返回所需的结果。

我的正则表达式出了什么问题？

Answer 1

试试这个：

extension String {
    subscript (range: NSRange) -> String {
        let startIndex = self.startIndex.advancedBy(range.location)
        let endIndex = startIndex.advancedBy(range.length)

        return self[startIndex..<endIndex]
    }
}

let s = "The dog ate the cat."

let pattern = try! NSRegularExpression(pattern: "(\\w+)?\\s?dog\\s?(\\w+)?", options: [.CaseInsensitive])

let matches = pattern.matchesInString(s, options: [], range: NSMakeRange(0, s.characters.count))

for m in matches {
    print(s[m.rangeAtIndex(0)])

    let range1 = m.rangeAtIndex(1)
    if range1.location != NSNotFound {
        print("capture group 1:", s[range1])
    }

    let range2 = m.rangeAtIndex(2)
    if range2.location != NSNotFound {
        print("capture group 2:", s[range2])
    }
}

String的扩展名是可选的，但它可以更轻松地使用NSRange。使用(\\w+)?使2个捕获组成为可选项，因此它也匹配以下字符串：

// The dog ate the cat
The dog ate
capture group 1: the
capture group 2: ate

// dog ate my home work
dog ate
capture group 2: ate

// I love my dog
my dog
capture group 1: my

// dog
dog

如何捕捉正则表达式模式周围的单词？

1 个答案: