(Resending something that was accidentally off-list.)
> On Nov 1, 2016, at 11:09 PM, Jens Alfke via swift-users
> <swift-users@swift.org> wrote:
>
> I don’t think the ExpressibleByStringInterpolation protocol provides enough
> information to make this work. It hands the implementation a list of values
> to concatenate, some of which are strings, but as far as I can tell there’s
> no way to tell which of those strings are the pieces of the string literal
> and which of them are the results of expressions.
There's actually a simple trick. The even-indexed elements are literal strings;
the odd-indexed ones are interpolated values. This is true even if you have two
interpolations adjacent to each other—there will be an empty string between
them. I've used this for a few different things, including a LocalizableString
type in Swift 2 and a SQLStatement type in Swift 3.
https://gist.github.com/brentdax/79fa038c0af0cafb52dd
https://github.com/brentdax/swift-sql/blob/master/Sources/SQLStatement.swift
> If I’m wrong about this, show me a workable implementation of it. :)
See above. :^)
> Also, ExpressibleByStringInterpolation is marked as being deprecated and will
> be “replaced or redesigned in Swift 4.0.” Maybe to solve this limitation?
I believe that making it easier to treat the literal and interpolated segments
differently is one of the goals.
--
Brent Royal-Gordon
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