Objective C: using non latin letters in NSURL objects corrupt custom URL schemes on iOS

Question

I want to add custom URL schemes to my app. I made it, but i found that if I use a NSString that contain not a latin letters as a parameter in my URL, my app doesn't open.

My aim is to share string like: myapp://?text=blabla, but on "blabla" place might be any string or maybe emoji. According to RFC 1808, URL can contain only latin letters and this looks very strange to me because what if I want to share text in french language or russian, or asian characters?

So, is there a way to do this anyhow?

Answer 1

RFC 1808 is obsoleted by RFC 3986. You care about Section 2 here. The fragment allows:

  fragment    = *( pchar / "/" / "?" )
  pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
  unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
  pct-encoded = "%" HEXDIG HEXDIG
  sub-delims  = "!" / "$" / "&" / "'" / "(" / ")"
              / "*" / "+" / "," / ";" / "="

As you note, "ALPHA" here means "the basic Latin alphabet," but calling this "Latin" will often confuse people unless you're very explicit, since Latin-1 is something different. In particular, the encoding NSISOLatin1StringEncoding is not "the basic Latin alphabet."

OK, lots of words, let's get to how to implement this. It's actually pretty simple, and Duncan's answer is close, but you shouldn't mess with the encoding. Still use UTF8 as normal:

NSString *escapedURL = [string stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

You want the percent-encoding to be based on UTF-8, and you always want Cocoa strings in UTF-8 unless you have a specific interoperability issue. As the docs say:

encoding: The encoding to use for the returned string. If you are uncertain of the correct encoding you should use NSUTF8StringEncoding.

Note that NSURL URLWithString: requires that you already have percent-escaped the string passed to it. That sometimes surprises people (also note that "Any percent-escaped characters are interpreted using UTF-8 encoding" as noted above).

Answer 2

You need to percent escape the special characters. Use the NSString method stringByAddingPercentEscapesUsingEncoding. Try passing in the NSNonLossyASCIIStringEncoding or perhaps NSISOLatin1StringEncoding. You'll have to play with encodings.