[Pharo-users] Re: ByteString asDate

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 <vonbecmann@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.