URLComponent percentEncodedPath - Is value valid before setting it - swift

Question

Trying to pass a string to URLComponents's percentEncodedPath crashes the app if the string is not a valid percent encoded path.
Is there a way to tell if the string is a valid percent encoded path before I set it? I am having trouble figuring this one out.
var urlComponents = URLComponents()
urlComponents.percentEncodedPath = "/some failing path/" // <- This crashes

Answer 1

You can do something like this:
extension String {
var isPercentEncoded: Bool {
let decoded = self.removingPercentEncoding
return decoded != nil && decoded != self
}
}
The rationale:
If the String is URL-encoded, removingPercentEncoding will decode it, and hence decoded will be different from self
If the String contains a percent (but is not URL-Encoded), removingPercentEncoding will fail, and hence decoded will be nil
Otherwise string will remain unmodified
Example:
let failingPath = "/some failing path/"
let succeedingPath = "%2Fsome+succeeding+path%2F"
let doubleEncoded = "%252Fsome%2Bfailing%2Bpath%252F"
let withPercent = "a%b"
failingPath.isPercentEncoded // returns false
succeedingPath.isPercentEncoded // returns true
doubleEncoded.isPercentEncoded // returns true
withPercent.isPercentEncoded // returns false
One disadvantage is that you are on a mercy of removingPercentEncoding and also this is a "mechanical" interpretation of the string, which may not take into account the implementation intent. For example a%20b will be interpreted as URL-encoded. But what if your app expects that string as a decoded one (and so it needs to be encoded further)?