nsstring - NSScanner 是否支持 Swift 字符串？

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"

但是如果我尝试使用“String”类型而不是“NSString”，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)

错误显示“无法将表达式的类型‘BOOL’转换为类型‘inout String？’”在 scanUpToString 行上。我什至不确定它指的是什么 BOOL。

那么，NSScanner 不支持 Swift String 类型吗？有没有我应该改用的新命令？

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。此代码将起作用:

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 "