Delphi problems inserting a string, Incompatible types error

Question

procedure TTelephoneNumberConverter.btnConvertClick(Sender: TObject);
var
  number: string;
  dupe: string;
  converted: string;
begin
  number := edtInput.Text ;
  dupe := Copy(number, 4, 1) ;
  converted := Insert(dupe , number , 4 ) ;
  pnlOutput.Caption := converted;
end;

Ok guys I just have a quick question regarding Delphi 2010 and inserting strings into other strings. The purpose of this small piece of code is to take the 4th character in a specific string and to duplicate it and add it next to the specific character e.g. 12345 -> 123445

The only problem is I keep getting an error :

Incompatible types 'string' and 'procedure, untyped pointer or untyped parameter'.

I am probably missing something small and stupid but would appreciate if someone could maybe answer my question.

I am probably missing something: You mean like the System.Insert documentation or the pop-up window that Code Insight gives you that tells you it's a procedure and not a function? — Ken White
– Ken White, Commented Feb 11, 2016 at 4:18

David Heffernan · Accepted Answer · 2016-02-10 18:28:02Z

2

Insert is a procedure that modifies its second argument.

Its signature is:

procedure Insert(Source: string; var Dest: string; Index: Integer);

The compiler error you see occurs because Insert does not return anything and thus cannot be the rhs of an assignment.

Your code should therefore be:

converted := number;
Insert(dupe, converted, 4);

Copy is overkill for a single character. Use [] instead:

dupe := number[4];

answered Feb 10, 2016 at 18:28

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Deltics Over a year ago

Something to note is that if you are to use direct character indexing then you also need to add a length check to deal with a number less than 4 characters in length, to avoid the exception that number[4] will then result in. Copy avoids this since it will simply return an empty string if the input string is shorter than the indicated start position resulting in a no-op when number is < 4 characters in length. Adding those safeguards for an insignificant (in this case) efficiency gain is arguably greater overkill than simply leveraging the safeguards already built in to Copy().

Collectives™ on Stack Overflow

Delphi problems inserting a string, Incompatible types error

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related