> Looks good, but you'll want some error handling. There's no clean way to
> integrate it with Generator because the protocol doesn't allow the
> implementation to throw, unfortunately. (I've run into the same problem
> building a Generator around a database query.) I think the best solution is
> to add a property that returns the NSStream.streamError, or a checkError()
> method that throws the current error if any, and have the caller use those at
> the end of the iteration.
You can do better.
extension NSInputStream {
// I will assume you already have a byteGenerator method (which
you can use with a for loop)
// with a checkError() method (which throws if the generation
terminated due to an error). However,
// you've made these private, and will use them to implement
this safe public API.
public func withByteGenerator<R>(blockSize: Int = 1024,
iterate: @noescape (NSInputStream.ByteGenerator) throws -> R) throws -> R {
let generator = byteGenerator(blockSize: blockSize)
let result = iterate(generator)
try generator.checkError()
return result
}
}
Now you write:
guard let stream = NSInputStream(fileAtPath: path) else {
…
}
try stream.withByteGenerator {
// XXX This would all be more complicated if CharacterGenerator
can throw, too.
for (i, line) in LineGenerator(source:
CharacterGenerator(source: $0, decoder: UTF8())).enumerate() {
print("\(i+1): \(line)")
}
}
(I'm assuming that these generators take their almost-automatic Sequence
conformance, of course.)
--
Brent Royal-Gordon
Architechies
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