Assigned(ErrorMessage) problem.

[Ian Branch 121]

Hi Team,

I have a function definition of ..

function ValidEmail(const EmailAddress: string; out ErrorMessage: string): Boolean;
const
  EMAIL_REGEX = '^((?>[a-zA-Z\d!#$%&''*+\-/=?^_`{|}~]+\x20*|"((?=[\x01-\x7f])' + '[^"\\]|\\[\x01-\x7f])*"\x20*)*(?<angle><))?((?!\.)' +
    '(?>\.?[a-zA-Z\d!#$%&''*+\-/=?^_`{|}~]+)+|"((?=[\x01-\x7f])' + '[^"\\]|\\[\x01-\x7f])*")@(((?!-)[a-zA-Z\d\-]+(?<!-)\.)+[a-zA-Z]' +
    '{2,}|\[(((?(?<!\[)\.)(25[0-5]|2[0-4]\d|[01]?\d?\d))' + '{4}|[a-zA-Z\d\-]*[a-zA-Z\d]:((?=[\x01-\x7f])[^\\\[\]]|\\' + '[\x01-\x7f])+)\])(?(angle)>)$';
var
    ....
    ....

The requirement is two fold.

1.  ErrorMessage is optional in the calling program.  i.e. it may be just - if validemail('myemail@somewhere.com') then ....

2.  Assign an error message to ErrorMessage if the construction of the email address is incorrect.

    if (not Result) and Assigned(ErrorMessage) then
      ErrorMessage := 'The following email addresses are invalid: ' + String.Join('; ', InvalidEmails.ToArray);

My problem is that I get an 'Incompatible types' error message for the 'then' in the above.

I don't understand why.  If I have read the help correctly, Assigned(Errormessage) should return a true or false, depending if Errormessage has been 'called'.??

Can somebody enlighten me please?

What do I need to do to meet my needs?

 

Regards & TIA,

Ian

[programmerdelphi2k 235]

"ErrorMessage" is a "string", then is not same than an object/property-event for example, to Assigned()  usage. you should use:

if ErrorMessage = ''  or ErrorMessage.IsEmpty... then...

but in your case above, it start "empty"

 

but you cannot known if "it" was defined or not, normally, it should be referenced in the source, like:

 

var

   LText:string;

begin

  ValidEmail( xxxxx, LText);  

 

because "out ErrorMessage" that needs a "var" to received value returned when out-scope.

 

"out" is almost the same than "var"

out  = out

var = in/out

Edited April 25, 2023 by programmerdelphi2k

[programmerdelphi2k 235]

21 minutes ago, Ian Branch said:

if (not Result)  then

ErrorMessage := 'The following email addresses are invalid: ' + String.Join('; ', InvalidEmails.ToArray);

else, LText will be "empty"!

Edited April 25, 2023 by programmerdelphi2k

[Ian Branch 121]

Hi p2k,

OK on the errormessage/object aspect.

 

16 minutes ago, programmerdelphi2k said:

but you cannot known if "it" was defined or not, normally, it should be referenced in the source

Quite so.  I use the basic routine in multiple locations/projects and it doesn't have the error message functionality.

I was looking to do a Global replace of old for new.

Then update the many calling instances at my leisure.

Edited April 25, 2023 by Ian Branch

[programmerdelphi2k 235]

now, you know "why" use "out Params" - always to receive/to transport some, never like "var Vars"

Edited April 25, 2023 by programmerdelphi2k

[Ian Branch 121]

How does one make a parameter such as this optional?

[programmerdelphi2k 235]

out needs always a var....

use some like this:

xxxx( xxxx; var AOut: string = "")

Edited April 25, 2023 by programmerdelphi2k

[Ian Branch 121]

But it still requires the parameter in the calling function.

[programmerdelphi2k 235]

see if possible  ... var AOut = "");

[Ian Branch 121]

Nope.

[programmerdelphi2k 235]

if using ... AOut=""); works.

then maybe needs change to

function xxxx(....): string;

[programmerdelphi2k 235]

type

  TRecResult = record

     b:boolean;

     m: string;

...

function xxxx(...): TRecResult;

[Ian Branch 121]

Mmmm.    Makes    "If not ValidEmail('khggh.jghfjgh.vbn') then ..." more complicated and I would still have to revist every call.

Thanks for your thoughts.

I guess I will have to vistit every call.

 

Regards & Tks again,

Ian

[Remy Lebeau 1260]

15 hours ago, Ian Branch said:

How does one make a parameter such as this optional?

Out parameters can't be optional.  You will have to overload the function instead, eg:

function DoValidateEmail(const EmailAddress: string; ErrorMessage: PString): Boolean;
begin
  ...
  if (not Result) and Assigned(ErrorMessage) then
    ErrorMessage^ := ...;
  ...
end;

function ValidEmail(const EmailAddress: string; out ErrorMessage: string): Boolean; overload;
begin
  Result := DoValidateEmail(EmailAddress, @ErrorMessage);
end;

function ValidEmail(const EmailAddress: string): Boolean; overload;
begin
  Result := DoValidateEmail(EmailAddress, nil);
end;

Alternatively:

function ValidEmail(const EmailAddress: string; out ErrorMessage: string): Boolean; overload;
begin
  ...
  if not Result then
    ErrorMessage := ...;
  ...
end;

function ValidEmail(const EmailAddress: string): Boolean; overload;
var
  LDiscarded: string;
begin
  Result := ValidEmail(EmailAddress, LDiscarded);
end;

 

[Ian Branch 121]

Hi Remy,

Great minds think alike.  There is my mind....

I was laying in bed at 2am mulling the issue, as you do, when it occurred to me that that was what I needed to do.

 

Regards & Tks,

Ian