> On Nov 11, 2016, at 11:54 AM, Muhammad Tahir Vali via swift-evolution > <[email protected]> wrote: > > Im curious to know the reasoning behind why implicit-wrapped optionals aren't > allowed when creating tuples. Below is an example with type aliases and > anonymous tuples. > > ex. > typealias Name = (first: String!, middle: String?, last: String!) > typealias Name = (first: String!, middle: String?, last: String!)! > var name : (first: String!, middle: String?, last: String!) > var name : (first: String!, middle: String?, last: String!)! > > error from all 4 examples above: > Implicitly unwrapped optionals are only allowed at top level and as function > results
This is intentionally-designed behavior. Preventing IUO at arbitrary locations was SE-0054: https://github.com/apple/swift-evolution/blob/master/proposals/0054-abolish-iuo.md <https://github.com/apple/swift-evolution/blob/master/proposals/0054-abolish-iuo.md> > I also noticed that I can modify tuples using functions ONLY if I use inout. > > func name(Person : inout (first: String?, middle: String?, last: String?)) { > Person.first = "John" > Person.last = "Doe" > } > > OR > > func name(Person : inout Name) { > Person.first = "John" > Person.last = "Doe" > } > > This is because tuples are passed into functions as 'let' constants. Why not > add the ability to modify a copy of the tuple inside the function ? We used to allow "var" parameters, but they were removed in SE-0003: https://github.com/apple/swift-evolution/blob/master/proposals/0003-remove-var-parameters.md <https://github.com/apple/swift-evolution/blob/master/proposals/0003-remove-var-parameters.md> Tuples are values like any other; I don't know why they would warrant a special exception to that rule. John.
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