There is simply no point in "taking the first nine numbers out".
And there shouldn't BE a test for the string being empty, anywhere.
'' '-' '---' and so on should all be handled the same way.
Oh well, what stops you doing
digits := aString select: [:each | each ~= $-].
digits size = 10 ifFalse: [^false].
lastDigit := digits la ost.
digits := digits copyFrom: 1 to: 9.
( (lastDigit = $X or: [lastDigit isDigit]) and: [
digits allSatisfy: #isDigit]
) ifFalse: [^false].
Now my code does not do this, but it is just 16 lines of code with
nothing that it would make sense to extract.
On Wed, 2 Sep 2020 at 22:24, Roelof Wobben <r.wob...@home.nl> wrote:
> Yep, I know that isValidIsbn is the method that must output if a isbn is
> valid or not.
>
> What I want to do is take the first 9 characters out so I can convert
> them to a array of numbers where I can do the calculation on.
> And take out the last char so I can seperate test if that is a valid
> char. So between the 0 and 9 or a X
>
> I do not think I would have do all the checks in that only method
> because it would be a very big method then.
>
> but if I understand you well also the test if a string is empty should
> be called from the isValidIsbn method or even checked there.
>
> Roelof
>
>
>
