You can create a binary operator that tests the left-hand operand for nil, and passes the unwrapped value to the right-hand operand (a function taking one value), this operator can be made left-associative to allow chaining.
let m = String(contentsOfFile: "README.md") ??? Markdown where ??? is the operator described above. -- C. Keith Ray * https://leanpub.com/wepntk <- buy my book? * http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf * http://agilesolutionspace.blogspot.com/ > On Dec 11, 2017, at 9:07 AM, Magnus Ahltorp via swift-evolution > <swift-evolution@swift.org> wrote: > > >> 12 Dec. 2017 01:30 Jared Khan via swift-evolution >> <swift-evolution@swift.org> wrote: >> >> I'd like to propose a syntax addition that acts to ease some things that I >> believe should fall under the umbrella of 'optional chaining'. Optional >> chaining allows us to access the properties of an optional value and return >> nil if any link in that chain breaks. I propose we introduce syntax to allow >> similar chaining when passing optional valued parameters to functions that >> expect that parameter to be non-optional. > > 1. Am I right in assuming that you propose that the suffix operator "?" would > make the result of the surrounding method/function call optional, so that > a(b(c?)) would make the result of the "b" function call optional, but not the > "a" function call, and that it would be a(b(c?)?) if we would like to > propagate this two levels? > > 2. If that is the case, is that understandable/neat enough? How common would > you expect this to be? > > 3. For some reason, (in current Swift) the suffix operator "?" seems to be > allowed in intra-expression syntax, and only fails when the inter-expression > syntax is checked for optionality congruence. Is there a reason for this? I > would have expected that the congruence error "cannot use optional chaining > on non-optional value of type" would never be seen for a lone "?", since the > error message "'?' must be followed by a call, member lookup, or subscript" > would always be displayed first if it was checked first. The "." operator > checks intra-expression syntax first, before checking congruence. Is this a > sign that "?" as a suffix operator is already somewhat operational as an > operator for optional types? I have a faint recollection that it was doing > something in earlier versions of Swift. > > /Magnus > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
