我写了一个快速函数,它接受一个字符串和一个范围作为它的参数。如何检查字符串的范围是否有效?
编辑:无意义的例子
func foo(text: String, range: Range<String.Index>) ->String? {
// what can I do here to ensure valid range
guard *is valid range for text* else {
return nil
}
return text[range]
}
var str = "Hello, world"
let range = str.rangeOfString("world")
let str2 = "short"
let text = foo(str2, range: range!)
https://stackoverflow.com/questions/39553748
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