Title: How to Declare and Initialize Constant Arrays in Delphi
In Delphi, arrays allow a developer to refer to a series of variables by the same name and to use a number (an index) to tell them apart.
In most scenarios, you declare an array as a variable - thus allowing for array elements to be changed at run-time.
Sometimes, you need to declare a constant array - a read-only array. You cannot change the value of a constant or a read-only variable. Therefore, while declaring a constant array you have to initialize it.
Here are a few examples of declaring and initializing constant arrays in Delphi:
type
TShopItem = record
Name : string;
Price : currency;
end;
const
Days : array[0..6] of string =
(
'Sun', 'Mon', 'Tue', 'Wed',
'Thu', 'Fri', 'Sat'
) ;
CursorMode : array[boolean] of TCursor =
(
crHourGlass, crSQLWait
) ;
Items : array[1..3] of TShopItem =
(
(Name : 'Clock'; Price : 20.99),
(Name : 'Pencil'; Price : 15.75),
(Name : 'Board'; Price : 42.96)
) ;
The above code declares and initializes three constant arrays, named: "Days", "CursorMode" and "Items".
"Days" is a string array of 6 elements. Days[1] returns the "Mon" string.
"CursorMode" is an array of two elements, where by declaration CursorMode[false] = crHourGlass and CursorMode = crSQLWait. "cr*" constants can be used to change the current screen cursor.
var
isDatabaseOperation : boolean
begin
isDatabaseOperation := true;
//changes the cursor to crSQLWait
Screen.Cursor := CursorMode[isDatabaseOperation];
"Items" defines an array of 3 TShopItem records.
Note: trying to assign a value for an item in a constant array raises the "Left side cannot be assigned to" compile time error, as in:
Items[1].Name := 'Watch'; //will NOT compile