see chapter 13 in http://files.pharo.org/books-pdfs/deep-into-pharo/2013-DeepIntoPharo-EN.pdf
it's a chapter dedicated to exceptions. the #on:do: message is in section 13.4. regarding the asDate message, i really don't know. you need a kind of validator. sorry, if i'm not much help. On Wed, Mar 2, 2022 at 7:35 AM Robert Briggs via Pharo-users < pharo-users@lists.pharo.org> wrote: > Thanks Bernardo > > > > That construct works as required, however I’m not sure what the semantic > difference is to my original. I seems counterintuitive. Could you expand > on what is going on for my benefit (if you have time). > > Again thanks. > > > > Also do you have a view on my description of the asDate result, and > whether it should self-validate the receiver and raise an exception? > > > > Regards > > R > > > > *From: *Bernardo Ezequiel Contreras <vonbecm...@gmail.com> > *Reply to: *Any question about pharo is welcome < > pharo-users@lists.pharo.org> > *Date: *Tuesday, 1 March 2022 at 15:05 > *To: *Any question about pharo is welcome <pharo-users@lists.pharo.org> > *Subject: *[Pharo-users] Re: ByteString asDate > > > > try to send the #on:do: message to a block. try this > > > > ^ [ (Date readFrom: self pattern: ‘dd/mm/yyyy’). > > true ] on: DateError do: [ false]. > > > > > > > > On Tue, Mar 1, 2022 at 11:52 AM Robert Briggs via Pharo-users < > pharo-users@lists.pharo.org> wrote: > > I may be being stupid but the current Date Class does not appear to > protect itself against a ByteString that is not in valid date format, e.g. > by raising an Error. > > > > e.g. the code ‘ABC’ asDate opens the Debugger on #isLetter was sent to > nil because it appears to expect more letters after $C but the peek > returns nil instead. > > This seems to me to require a more defensive programming approach. > > > > I would like to validate a user input as a valid date in a number of > different formats before converting it to a Date and storing it in my model. > > > > I’ve tried using the Date parser, e.g. > > > > Date readFrom: '04/02/2013' readStream pattern: 'dd/mm/yyyy'. > > > > > > This is fine for simply parsing a valid string but rates a DateError if it > doesn’t match the . So entering ‘04/13/2013’ cleverly raises ‘DateError: > There is no 13th month’. > > > > My thought was I could use this to return a simple true/false result in a > ByteString extension in my application for example as follows: > > > > ByteString >> isValdiDate > > > > (Date readFrom: self pattern: ‘dd/mm/yyyy’) on: DateError do: [^ false]. > > ^ true > > > > However this doesn’t intercept the DateError which is simply reported in > the Debugger as before. This may be my lack of uncderstaning of the > Exception handling in Pharo. > > > > Any and all thoughts welcome. > > > > R > > > > > > > > > > > > > > > -- > > Bernardo E.C. > > > > Sent from a cheap desktop computer in South America. > -- Bernardo E.C. Sent from a cheap desktop computer in South America.
