• Vincent (11/11) May 19 2009 Hello, guys!
• HOSOKAWA Kenchi (7/21) May 19 2009 We face related problem; classinfo mutability.
• Daniel Keep (5/19) May 19 2009 It doesn't matter; getMembers doesn't currently DO anything. Even if
• Jacob Carlborg (28/42) May 19 2009 You can use tupleof for classes and structs which returns a tuple

Vincent <thornik gmail.com> writes:

Hello, guys!
I have a question related D's introspection. I try to solve serialization task
(implementing JSON protocol)
and stuck at very start: getting all class' fields with types, names and
values. Just test code:

    Thread d;
    foreach(mi; d.classinfo.getMembers(null))
13:     writefln(mi.name);

test.d(13): Error: function object.MemberInfo.name () does not match parameter
types ()
test.d(13): Error: mi.name can only be called on a mutable object, not
const(MemberInfo)

I'm confused with such strange error: what is a problem with using MemberInfo?
I just try to GET info, not WRITE!
Anybody have idea how to get info about members? (see task above)
Thanks.

HOSOKAWA Kenchi <hskwk inter7.jp> writes:

Vincent Wrote:

 Hello, guys!
 I have a question related D's introspection. I try to solve serialization task
(implementing JSON protocol)
 and stuck at very start: getting all class' fields with types, names and
values. Just test code:
 
     Thread d;
     foreach(mi; d.classinfo.getMembers(null))
 13:     writefln(mi.name);
 
 test.d(13): Error: function object.MemberInfo.name () does not match parameter
types ()
 test.d(13): Error: mi.name can only be called on a mutable object, not
const(MemberInfo)
 
 I'm confused with such strange error: what is a problem with using MemberInfo?
I just try to GET info, not WRITE!
 Anybody have idea how to get info about members? (see task above)
 Thanks.


We face related problem; classinfo mutability.
my post is article_id=90722.
I have noticed that classinfo relates core of D's class system.

http://www.digitalmars.com/d/2.0/phobos/object.html
A pointer to this appears as the first entry in the class's vtbl[]. 

It seems that this problem must be treated carefully.

Daniel Keep <daniel.keep.lists gmail.com> writes:

Vincent wrote:
 Hello, guys!
 I have a question related D's introspection. I try to solve serialization task
(implementing JSON protocol)
 and stuck at very start: getting all class' fields with types, names and
values. Just test code:
 
     Thread d;
     foreach(mi; d.classinfo.getMembers(null))
 13:     writefln(mi.name);
 
 test.d(13): Error: function object.MemberInfo.name () does not match parameter
types ()
 test.d(13): Error: mi.name can only be called on a mutable object, not
const(MemberInfo)
 
 I'm confused with such strange error: what is a problem with using MemberInfo?
I just try to GET info, not WRITE!
 Anybody have idea how to get info about members? (see task above)
 Thanks.

It doesn't matter; getMembers doesn't currently DO anything.  Even if
you cast away the const-ness, you'd get no results.

You have to do this at compile-time with a concrete type for now.

  -- Daniel

Jacob Carlborg <doob me.com> writes:

Vincent wrote:
 Hello, guys!
 I have a question related D's introspection. I try to solve serialization task
(implementing JSON protocol)
 and stuck at very start: getting all class' fields with types, names and
values. Just test code:
 
     Thread d;
     foreach(mi; d.classinfo.getMembers(null))
 13:     writefln(mi.name);
 
 test.d(13): Error: function object.MemberInfo.name () does not match parameter
types ()
 test.d(13): Error: mi.name can only be called on a mutable object, not
const(MemberInfo)
 
 I'm confused with such strange error: what is a problem with using MemberInfo?
I just try to GET info, not WRITE!
 Anybody have idea how to get info about members? (see task above)
 Thanks.

You can use tupleof for classes and structs which returns a tuple 
containing all the fields of the class/struct. The following code will 
print the type, name and value of every field in the struct. BTW you can 
change private fields with tupleof. This is tested dmd v1.043 and Tango.

struct Struct
{
	private int i = 3;
	private char c = 'a';
}

Struct s;

foreach (i, t ; typeof(Struct.tupleof))
{
	const len = Struct.stringof.length;
	const fieldName = Struct.tupleof[i].stringof[1 + len + 2 .. $];
	const typeName = typeof(Struct.tupleof[i]).stringof;
	
	Stdout.formatln("type: {0}", typeName);
	Stdout.formatln("name: {0}", fieldName);
	Stdout.formatln("value: {0}", s.tupleof[i]);
	Stdout().newline;
}

type: int
name: i
value: 3

type: char
name: c
value: a