> On Jun 30, 2017, at 4:44 PM, David Baraff via swift-users
> <swift-users@swift.org> wrote:
>
> I know, I’ve read tons about about this. I sympathize. Unicode, it’s all
> very complex.
>
> But.
>
> BUT.
>
> Python:
> shortID = longerDeviceID[-2:] # give me the last two
> characters
>
> Swift:
> let shortID =
> String(longerDeviceID.characters.dropFirst(longerDeviceID.characters.count -
> 2))
>
> I can’t even read the above without my eyes glazing over. As has been
> pointed out, an API which demands this much verbosity is crippling for many
> developers, to say the least.
>
> With Swift 4, am I correct that it will be at least:
>
> let shortID = String(longerDeviceID.dropFirst(longerDeviceID.count - 2))
Hey, look on the bright side. They could have done what they’ve done with Data;
make it *look* like simple integer subscripts will work, when actually they
will blow up in your face at runtime.
func parseSome(data: Data) {
let magic = data[0..<4]
}
That’ll read the first four bytes of ‘data’ into ‘magic’, right? Well, not if
someone does this when calling the function:
func parseSome(data: inputData[someStart..<someEnd])
Now the ‘data’ your function has received is actually a slice, and when it
tries to access index 0, it’ll actually access the first byte of the original
data the slice was made from, *not* the first byte of the slice! On the
currently available version of Xcode, that’ll read the wrong data; with the
current sources from the trunk, it’ll crash. Either way, you won’t know until
runtime.
Charles
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