String formatting with characters is crashing - ios

Question

var modifiedString: String {
var outString = String()
for thisChar in self.characters {
if (thisChar == " "){
outString.appendingFormat("%%02X",thisChar ) // This line is asking me unwrap as CVarArg
outString.appendingFormat("%%02X",thisChar as! CVarArg) // This line crashes
}
}
}
}
I am trying to use outString.appendingFormat("%%02X",thisChar )
But this line is forcing me to unwrap as CVarArg but it is crashing when I am doing it. what is wrong in this

Answer 1

I assume this is placed in a String extension.
The error occurs because Character does not conform to CVarArg. Instead of converting the character directly to CVarArg, you need to convert it to a type that conforms to CVarArg. Here, the best choice would be String:
outString.appendingFormat("%%02X", "\(thisChar)")
You are also missing a return statement.
However, even if you did this and your code compiles, the property you wrote still does not make much sense. I don't think it works as you intended it to, but without more information I can't really be sure.

Answer 2

Use this code-
var modifiedString: String {
var outString = String()
for thisChar in self.characters {
if (thisChar == " "){
// outString = outString.appendingFormat("%%02X",thisChar.description )
outString = outString.appendingFormat("%%02X", "\(thisChar)")
}
else
{
outString = outString.appending("\(thisChar)")
}
}
return outString
}
Hope this helps!

Answer 3

It is not clear enough what you want to do, but I guess you want to do something like this:
extension String {
var modifiedString: String {
var outString = ""
for thisChar in self.characters {
if thisChar == " " {
let charCode = String(thisChar).unicodeScalars.first!.value
outString += "%" + String(format: "%02X", charCode)
//### Or if you prefer... (Do not miss, you need 3 '%'s in the format string.)
//outString = outString.appendingFormat("%%%02X", charCode)
} else {
outString.append(thisChar)
}
}
return outString
}
}
print("what you really want to do?".modifiedString)
//->what%20you%20really%20want%20to%20do?
With looping with for thisChar in self.characters, the type of thisChar becomes Character, it's not easy to get a character code from Character in Swift.
There may be some better ways but let charCode = String(thisChar).unicodeScalars.first!.value works as expected, when thisChar contains only one UnicodeScalar.
And you should better know Swift has a method named addingPercentEncoding:
let result = "what you really want to do?".addingPercentEncoding(withAllowedCharacters: CharacterSet.whitespaces.inverted)!
print(result)
//->what%20you%20really%20want%20to%20do?