Few people know about a Delphi language feature that has been present since Delphi 1: prepending the type definition with a type keyword to make the type getting a new identity.
Each time I use it, I have to do some browsing for the consequences, and this time I wrote down some notes and created a small example program (source is also below).
This time I needed it when writing class wrappers on top of the Delphi bindings for WebSphere MQ.
WebSphere MQ has Queues where you can put and get messages. It also has Queue Managers to which you connect, and that provide queuing services and manages queues.
Both Queues and Queue Managers have names that can be up to 48 (single byte) characters long.
Those names mean totally different things, so though the have similar data types, they have a different identity.
The same holds for 20 byte character arrays (they can be used as names for ChannelName, ShortConnectionName and MCAName). The 264 byte character array is so far used for ConnectionName only.
Distinguishing those types: That’s what “type types” in Delphi are all about. Read the rest of this entry »
The Wiert Corner - irregular stream of stuff 