Swift无法将Range分配给变量？

Question

我正试图想出一种从HTML页面中提取图像的方法.(我还没有看到这是如何实际完成的,我只是想从头开始提出一些事情,所以不要判断)无论如何,到目前为止我编写的代码都会出错"Cannot assign a value of type Range<Index>? to a value of type Range<Int>?"

//variable "html" has type String
        let variations = ["img","IMG","Img"]
        var tagStart: Range<Int>?
        var index = 0
        repeat
        {
           tagStart = html.rangeOfString(variations[index]) //Cannot assign a value of type Range<Index>? to a value of type Range<Int>?
            index += 1
        }while( tagStart == nil );

好的,所以Range的类型是Index,而不是Int.但是当我尝试更改声明时,我收到"Use of undeclared type 'Index'"错误.所以现在它告诉我索引是我想象中的一个虚构？

//variable "html" has type String
        let variations = ["img","IMG","Img"]
        var tagStart: Range<Index>?
        var index = 0
        repeat
        {
           tagStart = html.rangeOfString(variations[index]) //"Use of undeclared type 'Index'"
            index += 1
        }while( tagStart == nil );

Answer 1

什么rangeOfString产生不是指数的范围; 它是一系列String.Index.