Overview

This blog post looks at Enums and how multi-platform generics and RTTI (or what C# guys call reflection) make this really simple using common code on Windows, Mac OS X, iOS and Android using Delphi.

Starting with what an Enum is, the post then explores how you would traditionally have seen it written in code, before looking at the clean X-platform approach RTTI and Generics provide.

If your experienced in working with enums and want to find out how RTTI makes it easier, you may want to skip the first part of this post and get to the section about RTTI further down.

Enumerated Types to and from strings

An Enum, or Enumerated Type is a data type with a set of named values.

Enums are a great way to define a set of constants that are specific for a type and work with them in context, ensuring only one, or an array of allowed values is set.

OK, I’m going to use an example that maybe should have more values listed, but you get the point. It is the points of a compass – North, South, East or West.

type
  TCompass = (North, South, East, West);

var
  D : TCompass; // short version for Direction 
begin
  D := TCompass.North;
  case D of 
    North : ShowMessage('North');
    South : ShowMessage('South');
    East  : ShowMessage('East');
    West  : ShowMessage('West');
    raise Exception.Create('Unknown Direction');
  end;
end;

This provides one way to convert a Enum to a string using a case statement, but every time you make a change to your Enum types, you need to add in extra code… Call me lazy, but thats too much work!

Continue reading Using Generics & RTTI to get enum string name or enum value →