下面的第一个代码表现出不稳定的行为，你不应该使用它.(请参阅本答案的后半部分.)

The first code below have shown unstable behaviour and you should not use it. (Please see the latter part of this answer.)

在可失败的初始化程序中添加一行:

Add one line to your failable initializer:

        do {
            try self.init(pattern: pattern, options: regexOption)
        } catch {
            print(error)
            return nil //->you need to return nil to tell initialization failed
        }

(我认为 Swift 编译器应该警告这个缺失的 return nil.可能是 Swift 的一个错误?)

(I think Swift compiler should warn about this missing return nil. May be a bug of Swift?)

之后，您可以安全地检查结果是否为零:

After that you can safely check the result if it's nil or not:

let sOpts = SearchOptions(searchString: "\\", replacementString: "", matchCase: false, wholeWords: false)
if let regex = NSRegularExpression(options: sOpts) {
    //Use regex
    print(regex)
} else {
    //Process errors
    print("Something bad in SearchOptions")
}

(我省略了 escapeMetacharacters，因为它还没有使用.)

(I omitted escapeMetacharacters, as it's not used yet.)

据我测试，使用静态方法从未崩溃过.

As far as I tested, using static method has never crashed.

extension NSRegularExpression {
    static func expresssionWith(options: SearchOptions) -> NSRegularExpression? {
        let searchString = options.searchString
        let isCaseSensitive = options.matchCase // set to true
        let isWholeWords = options.wholeWords // set to false

        // handle case sensitive option
        var regexOption: NSRegularExpressionOptions = .CaseInsensitive
        if isCaseSensitive { // if it is match case remove case sensitive option
            regexOption = []
        }

        // put the search string in the pattern
        var pattern = searchString

        if isWholeWords {
            pattern = "(?<!\\w)" + NSRegularExpression.escapedPatternForString(searchString) + "(?!\\w)"
        }

        do {
            return try NSRegularExpression(pattern: pattern, options: regexOption)
        } catch  {
            print(error)
            return nil
        }
    }
}

let sOpts = SearchOptions(searchString: "\\", replacementString: "", matchCase: false, wholeWords: false)

if let regex = NSRegularExpression.expresssionWith(sOpts) {
    //Use regex
    print(regex)
} else {
    //Process errors
    print("Something bad in SearchOptions")
}