> On Jul 26, 2017, at 9:55 AM, Robert Bennett <[email protected]> wrote:
>
> Is there a reason that a throwing unwrap function/operator isn’t part of the
> standard library? Seems like it would be handy to be able to have a one-liner
> for attempting to unwrap and throw if it’s nil.
?! would be the wrong name, since ! is generally reserved for
potentially-trapping operations that should be avoided in most cases.
If you’re going to explore this branch of the design tree, the sensible thing
seems to be to (conceptually) carve off some chunk of the operator space for
throwing operators (e.g. ^ which could be rationalized as connoting “raising”
an error). This would argue for postfix ^ to unwrap-or-throw (as an analog to
postfix ?, enabling chaining etc), and would then provide a schema to define
other “or throw” operations.
-Chris
> Something like
>
>
> postfix operator .?!
>
> extension Optional {
> static postfix func .?!(optional: Optional<Wrapped>) throws -> Wrapped {
> switch optional {
> case let .some(wrapped):
> return wrapped
> case .none:
> throw UnwrapError()
> }
> }
> }
>
> init?(data: [String: Any]) {
> do {
> self.someProperty = try data["some_key”].?!
> self.anotherProperty = try data["another_key”].?!
> } catch is UnwrapError {
> return nil
> }
> }
>
>
>> On Jul 26, 2017, at 12:13 PM, Chris Lattner via swift-evolution
>> <[email protected]> wrote:
>>
>>
>>> On Jul 25, 2017, at 2:44 AM, philohan95 via swift-evolution
>>> <[email protected]> wrote:
>>>
>>> I think the current way to initiate models in a Failable Initializer
>>> `init?()` is overly verbose and should be shortened down so less
>>> boilerplate should be needed.
>>>
>>> The current way:
>>>
>>> ```
>>> let someProperty: Any
>>> let anotherProperty: Any
>>>
>>> init?(data: [String: Any]) {
>>> guard
>>> let someProperty = data["some_key"],
>>> let anotherProperty = data["another_key"]
>>> else {
>>> return nil
>>> }
>>>
>>> self. someProperty = someProperty
>>> self. anotherProperty = anotherProperty
>>> }
>>> ```
>>
>> Guard isn’t really the right answer for this, I’d try something like this
>> (where unwrapOrThrow is the obvious generic function you can define
>> yourself):
>>
>> init?(data: [String: Any]) {
>> do {
>> self.someProperty = try unwrapOrThrow(data["some_key”])
>> self.anotherProperty = try unwrapOrThrow(data["another_key”])
>> } catch {
>> return nil
>> }
>> }
>>
>> -Chris
>>
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>
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