Enable usage of C string placeholder: %s

[schroepf]

For cross platform projects it is often important to have shared strings and translations for android and iOS. But using format strings which contain string placeholders cannot be done in a consistent way for both platforms, as swift cannot easily handle the c string placeholder %s.

Using R.swift strings containing these kind of placeholders are generated to take arguments of type: UnsafePointer<unichar>, but I found no way to put a unichar pointer into the function and produce meaningful output. It seems that unichar is the wrong type to use for String(format: format, locale: locale, value1) which seems to work with 8 bit chars, not 16 bit chars.

So I think that changing the generated type for %s placeholder from UnsafePointer<unichar> to UnsafePointer<CChar> would allow us to work with these kind of format string.

I patched R.swift locally with this change and it seemed to work:

Following code in Localizable.strings:

"test_string" = "Test %1$s, %2$s, %3$s";

produces now the following code in R.generated.swift:

      static func test_string(_ value1: UnsafePointer<CChar>, _ value2: UnsafePointer<CChar>, _ value3: UnsafePointer<CChar>, preferredLanguages: [String]? = nil) -> String {
        guard let preferredLanguages = preferredLanguages else {
          let format = NSLocalizedString("test_string", bundle: hostingBundle, comment: "")
          return String(format: format, locale: applicationLocale, value1, value2, value3)
        }

        guard let (locale, bundle) = localeBundle(tableName: "Localizable", preferredLanguages: preferredLanguages) else {
          return "test_string"
        }

        let format = NSLocalizedString("test_string", bundle: bundle, comment: "")
        return String(format: format, locale: locale, value1, value2, value3)
      }

And this can now be used like so:

        let test = "one".withCString { one in
            "two".withCString { two in
                "three".withCString { three in
                    R.string.localizable.test_string(one, two, three)
                }
            }
        }

        print(test)

Output is:

Test one, two, three

[schroepf]

PR to fix this issue: #623

[schroepf]

With an extension like:

extension String {
    var cstring: UnsafePointer<CChar> {
        (self as NSString).utf8String!
    }
}

Usage of the generated function is even easier:

print(R.string.localizable.test_string("one".cstring, "two".cstring, "three".cstring))

[tomlokhorst]

https://github.com/mac-cain13/R.swift/pull/623 is merged