> On Apr 24, 2016, at 2:33 PM, Chris Lattner via swift-evolution
> <[email protected]> wrote:
>
>
>> On Apr 21, 2016, at 12:42 AM, Daniel Höpfl via swift-evolution
>> <[email protected]> wrote:
>>
>> Hi there!
>>
>> TL;DR: Here’s my idea for a better localized strings handling in Swift.
>> It includes both, support for string interpolation support for
>> NSLocalizedString, and a new string delimiter `...` that can be used
>> instead of NSLocalizedString("...”).
>
> FWIW, this is closely related to the idea of extending string interpolation
> to support generalized “printf” style modifiers, which would allow very
> expressive formatting inline in a string interpolation. This has not yet
> come to pass, but a write up of the ideas are available here:
> https://github.com/apple/swift/blob/master/docs/TextFormatting.rst
Actually, it looks like the interesting point didn’t make it into the formal
writeup. The idea was to enable something like this (just a sketch):
public protocol CustomStringConvertible {
/// A textual representation of `self`.
var description: String { get }
func formattedDescription(format: String) -> String { get }
}
Int could then implement support for “x” to print hexadecimal, we could support
left/right whitespace padding, and custom types could provide their own custom
formatters (e.g. a string could have a title case formatter, or a "look up
localized form of” modifier). We could then provide a “printf” that would
allow traditional “%x0” substitutions. It could also be incorporated into the
string literal syntax by allowing something like:
let hashValue = 42 // not a good hash function
print(“Hashcode = \(hashValue:x)”)
This is just a sketch, but that’s the idea. It never went anywhere because we
didn’t have the language features in place to make it work, notably defaulted
implementations in protocols were missing at the time.
-Chris
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