What's the difference between public and published class members in Delphi?

delphi oop rtti delphi-6
Ondra C. picture Ondra C. · Jul 1, 2010 · Viewed 15.9k times · Source

Please could someone explain me what's the difference between public and published class members in Delphi?

I tried to look at Delphi help and I understand that these members have the same visibility, but I don't understand very well how they differ and when should I use published members instead of public ones.

Thanks a lot.

Answer

Andreas Rejbrand picture Andreas Rejbrand · Jul 1, 2010

The compiler generates RTTI (Run-Time Type Information) metadata for published members, but not for public members (by default). The main effect of this is that the published properties of an object will appear in the Object Inspector at design time.

I do not know if you are writing components, but if you do, you probably know that properties and events are normally published, so that they can be set using the Object Inspector.

Public

public
  property MyProperty: integer read FMyProperty write FMyProperty

MyProperty will not be visible in the Object Inspector.

Published

published
  property MyProperty: integer read FMyProperty write FMyProperty

MyProperty will be visible in the Object Inspector.

Related questions

Where are the Delphi Attributes Real World Examples?

I know by TMS Aurelius that we can use the "new" 2010 attributes feature to serialize database table fields into object properties at run-time, for example, and I am not an expert on this deep object oriented schema, so I look …

Read More
How can I declare an array property?

I constructed class system TTableSpec=class(Tobject) private FName : string; FDescription : string; FCan_add : Boolean; FCan_edit : Boolean; FCan_delete : Boolean; FFields : array[1..100] of TFieldSpec; public property Name: String read FName; property Description: String read FDescription; property Can_add : Boolean …

Read More
Reintroducing functions in Delphi

What was the motivation for having the reintroduce keyword in Delphi? If you have a child class that contains a function with the same name as a virtual function in the parent class and it is not declared with the …

Read More