Optional strings #2
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| self.description = dict["description"] as? String | ||
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| let overrides = try? dict["overrides"] | ||
| .flatMap { $0 as? [String: Any] }? |
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In this case we're actually flatMap'ing the Optional rather than the Collection
| if let val = value as? T { | ||
| return val | ||
| } | ||
| if let nilLiteralType = T.self as? ExpressibleByNilLiteral.Type { |
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Can you add some doc comments on this. I've read it about 10 times and think I'm understnading it now, but doesn't hurt to add something in to explain what is a pretty opaque piece of code without significant context.
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In the end, I'm assuming it's entirely because you can't convert NSNull to nil?
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Yeah, this was fun...
This is to handle the case where T: Optional. If the typecast to T fails (in this case NSNull.Type -> Optional<String>) we want to return nil, but in a way that isn't a failure.
nil can't be assigned to defaultValue for example, because as far as ConfigurationProperty knows it's not optional. We also can't construct the Optional directly, because we don't know the Wrapped type.
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Hopefully a bit clearer with that documentation.
Adds the definition of
String?asoptionalStringtoPropertyType, so we can construct optional strings as required.Most of the heavy lifting happens in
ConfigurationProperty, where previously we'd bail if converting the default value / overrides toTfailed.To detect whether conversion to
Tbeing nil isn't a failure, we check to see whetherT: ExpressibleByNilLiteral(Optional is the only thing that conforms to this). If it is, we have to do a bit of a dance to doT -> ExpressibleByNilLiteral -> Tso we can successfully initialise. The rest of it is relatively self-explanatory.