[swift-evolution] throw expressions in ternary operators

David Hart david at hartbit.com
Mon May 2 07:25:09 CDT 2016

I remember discussing something like this in swift-evolution but can’t find it. I was wondering if it was worth a proposal or not.

When constructing objects from dictionary of values, I often write the parsing of optional values as such:

age = try dictionary["age"].flatMap {
	if let age = $0 as? Int {
		return age
	} else {
		throw Error.InvalidFormat

Basically, I don’t want to throw if the dictionary does not contain an “age” key, but if it does, I want to throw if it is not an Int. I’m writing this way, but I’d like to write is as such:

age = try dictionary["age"].flatMap { $0 as? Int ?? throw Error.InvalidFormat }

But this causes a compilation error. Don’t you think the ternary operator should allow an expression that throws on the right hand side?

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