Parameter Passing an Array of Type in Delphi

Question

I'm trying to pass an array out of a class into my main program in Delphi. I'm having a bit of trouble with the data types and an hour scouring the web has found nothing to help me. It sounds a bit strange, but the more complex the answer the better (it's for a college project).

I have a class connected to SQL which reads an SQL Query into an array of a record Type declarations (sorry if it's a bit messy at the moment) :

Type TScout = Record
SNum, FName, SName, Gender, Address, HomeNum, MobNum,
SEmail, STel, Hikes, Nights, Med, Diet : String;
DoB, DoJ : String;
End;

Type TScoutArray = Array of TScout;

Type TScoutSQL = Class
Public
  Procedure InitSQL;
  Procedure GetRecords;
  Function SendRecords : TScoutArray;
Private
  ScoutsArray : TScoutArray;
  ScoutConnection : TSQLConnection;
  ScoutQuery : TSQLQuery;
End;

So the whole "Function SendRecords : TScoutArray;" isn't working, as on the other side I have the same 2 types (TScout and TScoutArray) declared exactly the same, I call the function:

  ScoutArray := ScoutSQL.SendRecords;

And I get:

[Error] MembersUnit.pas(51): Incompatible types

Can anyone help?

Record type declaration means a record, right? So, you read the data from a DBMS, store it in a record and try to pass a dynamic array of records around. You should also provide more code, like the type of ScoutArray. that is because TScoutArray and array of TScout are different types in Pascal/Delphi. — Trinidad
– Trinidad, Commented Feb 14, 2011 at 23:47
I made TScoutArray because I read you can't just pass an array out of a class, you have to make your own data type, but it still didn't work, so I asked here — Nick
– Nick, Commented Feb 15, 2011 at 8:53
if you found your answer you should mark it as accepted or supply more details if we haven't understood. — David Heffernan
– David Heffernan, Commented Feb 15, 2011 at 11:08
@David Heffernan Apologies for that. Now marked the answer. Thanks for answering swiftly and in a way I could easily understand. — Nick
– Nick, Commented Feb 16, 2011 at 15:01

David Heffernan · Accepted Answer · 2011-02-14 23:44:39Z

3

I suspect that your problem is that you are declaring these types twice in separate units. Doing so results in distinct, incompatible types.

What you need to do is to:

Declare the types, in the interface section, of one unit only (unit A, say).
In another unit (unit B, say) that wants to use these types you add unit A to the uses clause.

answered Feb 14, 2011 at 23:44

David Heffernan

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1 Comment

Gerry Coll Over a year ago

or add the type declaration into the interface section of a third unit C, and include C in both A and Bs USES clauses.

Trinidad · Accepted Answer · 2011-02-14 23:54:27Z

2

Wrong way

var
  badArray: array of TScout;
begin
  badArray := ScoutSQL.SendRecords;

This won't work. array of TScout and TScoutArray, the latter being what SendRecords returns, are different types in Delphi/Pascal.

Right way

var
  niceArray: TScoutArray;
begin
  niceArray := ScoutSQL.SendRecords;

answered Feb 14, 2011 at 23:54

Trinidad

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