Array as a Function Return Type and Method Parameter

Arrays in Delphi allow us to refer to a series of variables by the same name and to use a number (an index) to tell them apart.

Here's an example integer array that can hold up to 7 (integer) values. Note: this is a fixed-size static Delphi array declaration.

var DayVisitors : array[0..6] of Integer;

Arrays as Function Return Types

In Delphi, functions are routines that return a value.

When you want a function to return an array type variable, you might be tempted to use the next declaration:

function GetWeekTotal(weekIndex : integer) : array[0..6] of integer;
begin
  //this will NOT compile
end;

When you try to compile this code, you'll get the next compile-time error: [Pascal Error] E2029 Identifier expected but 'ARRAY' found.

Obviously, when you declare functions that will return array value, you cannot include index type specifiers return declaration.

In order to allow a function to return an array value, you first need to create a custom array type, then use it as a return function type:

//this WILL compile
type
  TDayVisitors = array[0..6] of integer;

...

function GetWeekTotal(weekIndex : integer) : TDayVisitors;
begin
  //do some calculation for the provided "week"
end;

Arrays as Method/Routine Properties

Similar to using arrays as function return types, when you declare routines that take array parameters, you cannot include index type specifiers in the parameter declarations.

type
  TDayVisitors = array[0..6] of integer;

...

procedure DisplayWeekTotal(weekVisitors : TDayVisitors) ;
begin
  //display some info for the provided "week"
end;

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