Prestwood IT Newsletter Apr 2009 Issue - Delphi Edition

In Delphi, you define constants similar to how you define variables but use the Const keyword instead of the Var keyword. Declare global constants in a unit's interface section and unit constants (scope limited to unit) in the implementation section. Declare local constants above the begin..end block.

How often have you started a new Delphi project, then spent some time fleshing out the default main form provided by Delphi?

This task only needs to be done once or twice. Delphi then allows us to re-use this work at the start of each new project.

Source code is included.

Declare global variables in the interface section of a unit, variables declared within the implementation section (but not within a method) have a scope limited to the unit. You declare local variables in a var block outside (above) your begin..end code block. You cannot declare variables in-line (inside begin..end). You can initialize global and unit variables but you cannot initialize local variables. Delphi offers many variable types. Some common variable types include String, WideString, PChar, Integer, Boolean, Single, Double, Pointer, and Variant.

procedure SomeProcedure;

var


  Fullname: String;


  Age: Integer;

  X, Y, Z: Double;

  MyArray: array [1..100] of Char;

begin

end;

//You can initialize global variables.

var

  ClickCounter: Integer = 0;

Can I call a DotNet DLL from my Delphi Win32 application? For example, with Delphi 7 or Delphi 2010?

It's not easy because the .NET RTL resides in a different process. You can wrap up the DotNet DLL into an ActiveX control and call it or have both your app and the DotNet DLL write to the registry, a file, etc. By the way, you CAN wrap up a Win32 DLL in a DotNet DLL and call it from DotNet.