From: "Marc A. Criley" <mcqnet@earthlink.net>
Subject: JGNAT and Null references
Date: Thu, 01 Mar 2001 17:23:31 GMT
Date: 2001-03-01T17:23:31+00:00 [thread overview]
Message-ID: <3A9E77D4.D40FEAA@earthlink.net> (raw)
Let me just plow right into an annotated example here, rather than
trying to explain it first...
The Java class javax.swing.JTabbedPane provides a method called addTab
that looks like this:
public void addTab(String title,
Icon icon,
Component component,
String tip)
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
which is perfectly correct since that P2_Icon parameter requires a
pointer to , or the "'access of" an actual object.
Buuuuuut, I don't have, or want to pass, an Icon to display with the
tab, and specifying "null" is how I would indicate that in Java. What
do I provide as a "null argument" in JGNAT? I was hoping to find some
sort of predefined "null_reference" constant, analogous to
System.Null_Address, but no such luck.
Thanks much,
Marc A. Criley
next reply other threads:[~2001-03-01 17:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-03-01 17:23 Marc A. Criley [this message]
2001-03-01 18:10 ` JGNAT and Null references James Rogers
2001-03-02 19:27 ` Stephen Leake
2001-03-03 21:17 ` Marc A. Criley
2001-03-04 2:46 ` Randy Brukardt
2001-03-05 13:05 ` Marc A. Criley
2001-03-05 16:28 ` tmoran
2001-03-06 0:57 ` Marc A. Criley
2001-03-05 18:11 ` Randy Brukardt
2001-03-05 20:44 ` Florian Weimer
2001-03-07 16:02 ` Tucker Taft
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