如何快速转换nil字符串

Question

I try to filter just the name of my peripheral.name object. Usually, that's no problem. For example: [Optional"Apple TV"] works like it should. But if I get a nil object, I get a fatal error and I don't understand why...

let str = "\(peripheral.name)"
let test_str = str.substringWithRange(Range<String.Index>(start:str.startIndex.advancedBy(10), end: str.endIndex.advancedBy(-2)))   
print(test_str)

I thought that the operation "\\(peripheral.name)" converts every object into a string... also a nil type.

Answer 1

str will always be a String indeed: if peripheral.name is nil, it will result in an empty string.

But you're using advancedBy with hardcoded values like 10: it won't work on an empty string, that's the source of your fatal error, you can't move along an index that doesn't exist.