Re: JGNAT and Null references

[James Rogers <jimmaureenrogers@worldnet.att.net>]

"Marc A. Criley" wrote:
> 
> When this class is run through JGNAT's jvm2ada, the Ada equivalent of
> that method is:
> 
>    procedure addTab (This : access Typ;
>                      P1_String : access java.lang.String.Typ'Class;
>                      P2_Icon : access javax.swing.Icon.Typ'Class;
>                      P3_Component : access java.awt.Component.Typ'Class;
>                      P4_String : access java.lang.String.Typ'Class);
> 
> Okay, so far so good.
> 
> In Java, if I don't have an icon to accompany this tab pane, I can just
> supply that parameter with a null:
> 
>    jtp.addTab("My title", null, a_component, "a_tool_tip");
> 
> Attempting this in Ada:
> 
>    AddTab(Jtp, +"My title", null, A_Component, +"a_tool_tip");
> 
> generates an error when compiled:
> 
>    null cannot be of an anonymous access type

This is easily handled by defining a constant value of a null access
type.

type Icon_Access is Access all javax.swing.Icon.Typ'Class;

Null_Icon : constant Icon_Access := Null;

Jim Rogers
Colorad Springs, Colorado USA