Question

我想知道为什么会这样（注意我使用的是NSString类型）：

    let stringToSearch:NSString = "I want to make a cake and then prepare coffee"
    let searchTerm:NSString = "cake"
    let scanner = NSScanner(string: stringToSearch)
    var result:NSString? = nil
    scanner.scanUpToString(searchTerm, intoString:&result)
    println(result) // correctly outputs "I want to make a"

但如果我尝试使用＆＃34; String＆＃34;类型而不是＆＃34; NSString＆＃34;，这将无法编译：

    let altStringToSearch:String = "I want to make a cake and then prepare coffee"
    let altSearchTerm:String = "cake"
    let altScanner = NSScanner(string: altStringToSearch)
    var altResult:String? = nil
    altScanner.scanUpToString(altSearchTerm, intoString:&altResult)
    println(result)

错误说＆＃34;无法转换表达式＆＃39; BOOL＆＃39;键入＆＃39; inout String？＆＃39;在scanUpToString行上。我不确定它甚至指的是BOOL。

那么，NSScanner无法使用Swift String类型吗？是否有我应该使用的新命令？

Answer 1

scanUpToString方法的第二个参数必须是指向NSString的指针。其他参数可以是String。这段代码可以使用：

let altStringToSearch:String = "I want to make a cake and then prepare coffee"
let altSearchTerm:String = "cake"
let altScanner = NSScanner(string: altStringToSearch)
var altResult:NSString?
altScanner.scanUpToString(altSearchTerm, intoString:&altResult) // altResult : "I want to make a "

NSScanner是否适用于Swift Strings？

1 个答案: