[solved] how to do a default string array parameter

[Joanna from IRC]

Hi everyone
I am trying to create a procedure that will use a default string array when no array is provided;

i want the default array to be fairly empty like this:

Code: Pascal  [Select][+][-]

1. const empty_array:array[0..0] of string = ('');  

when i try to declare the procedure however it doesn't compile..

Code: Pascal  [Select][+][-]

1. PROCEDURE INIT (CONST TBL_name:ShortString;CONST DATA_TYPE:TDATATYPE_CATEGORIES;const caps:TStringArray = empty_array );

I'm not sure of the syntax. I've only used default parameter with very simple values before. is it possible to do this or do i need to use overloaded init procedures, one with an array and one without ?

[korba812]

If the type TStringArray is a dynamic array then you can use the value "nil" as the default value.

Code: Pascal  [Select][+][-]

1.     PROCEDURE INIT (CONST TBL_name:ShortString;CONST DATA_TYPE:TDATATYPE_CATEGORIES;const caps:TStringArray = nil );

[Joanna from IRC]

works perfectly, thanks so much i can't believe i didn't think of using nil 

Code: Pascal  [Select][+][-]

1. PROCEDURE INIT (CONST TBL_name:ShortString;CONST DATA_TYPE:TDATATYPE_CATEGORIES;const caps:TStringArray = nil );

[Thaddy]

Apart from SHOUTING formatting, I would never  call a procedure INIT, because it is also tied in the language as a semi-reserved word for a constructor in TP mode. Which can clash if you need that mode.

[marcov]

(iirc    = [] works in trunk too)

[Thaddy]

(iirc    = [] works in trunk too)

() objfpc. You refer to mode delphi.

[PascalDragon]

I am trying to create a procedure that will use a default string array when no array is provided;

An important rule when dealing with default parameters: the default value can only be an untyped constant. So anything like your empty_array - which is a typed constant - is simply not valid. The only valid constant value for dynamic arrays is Nil as you learned by now.

[marcov]

(iirc    = [] works in trunk too)

() objfpc. You refer to mode delphi.

I always refer to mode Delphi.

[Joanna from IRC]

Sorry Thaddy  .. there are quite a few things in this project that would not work well with turbo pascal... especially the gui 

Although in my use case, the nil array works best it still is an interesting idea to have more complex things as default parameters. I tried using the address of a const array and that didn’t work either..

[Thaddy]

Joanna, mode objfpc is not mode TP.