Hi,
I want to store a TArrayD in a file, but it doesn’t work with array->Write(), because it is not derived from TObject.
The method for writing those objects mentioned in the User’s Guide (f->WriteObject(“array”, array)) does not work, too.
To write a useless Wrapper-Class which inherits from TObject is unsatisfying.
Is anybody experienced in this area? Code examples would be nice 
Thank you in advance. Johannes Kissel.
[quote]The method for writing those objects mentioned in the User’s Guide (f->WriteObject(“array”, array)) does not work, too.[/quote]How does it not work?
Philippe
On page 164 of the User’s Guide v5.14 “Saving Objects to Disk”:
For objects that do not inherit from TObject use:
My simple code for testing:
[code] // fill a TArrayD
int len = mxGetDimensions(prhs[0])[1];
TArrayD numbers(len, mxGetPr(prhs[0]));
// save it to file
TFile f(“test.root”, “recreate”);
f.WriteObject(numbers, “numbers”);
f.Close();
[/code]
And the result:
OK, I’m a C++ and ROOT beginner, but I just don’t get it… 
I think you should invoke the WriteObject method with a pointer to your TNumberD object.
That is,
f.WriteObject(&numbers, "numbers"); I get a segmentation violation. Maybe I do something wrong…
TVectorT seems to be, what I’m looking for. It inherits from TObject 
Thanks for your help.
[quote]I get a segmentation violation. Maybe I do something wrong…[/quote]I can not reproduce this. The following should work:
[code] // fill a TArrayD
int len = mxGetDimensions(prhs[0])[1];
TArrayD numbers(len, mxGetPr(prhs[0]));
// save it to file
TFile f(“test.root”, “recreate”);
f.WriteObject(&numbers, “numbers”);
f.Close(); [/code]
Philippe
Maybe my problems are caused by compiling it not with .L test.cpp++
[quote]Maybe my problems are caused by compiling it not with .L test.cpp++[/quote]If you are not compiling with “.L test.cpp++”, how are you compiling?
Philippe
I need ROOT as data storage in a MATLAB-Environment. That's why...
I guess some day I'll get rid of all those C++-Problems :wink: But at the moment my project is in progress and I'm happy with TVectorT.I need ROOT as data storage in a MATLAB-Environment. That’s why…
I guess some day I’ll get rid of all those C+±Problems But at the moment my project is in progress and I’m happy with TVectorT.
I just had a new look at the problem with the segmentation violation. I found out that this happens only when a file with not-TObject-derived-objects is opened in the object browser, whereas there’s no problem to load these objects in the CINT shell.
My error message:
*** Break *** segmentation violation
Using host libthread_db library "/lib/libthread_db.so.1".
Attaching to program: /proc/27663/exe, process 27663
[Thread debugging using libthread_db enabled]
[New Thread -1224513840 (LWP 27663)]
Failed to read a valid object file image from memory.
0xb7fd0410 in ?? ()
#1 0xbfc10ff8 in ?? ()
#2 0x00000000 in ?? ()
[size=75]Maybe this could be a bug in the browser…?[/size]
How can I determine an objects type if it’s not derived from TObject? I don’t know how to use the Class() method of TArray types.
Isn’t there any integer array type derived from TObject. I didn’t find one 
What’s the reason for so many base types? Is it historical?
Thank you for your answers!
You can get a tclassObject via:TClass::GetClass(classname)orTClass::GetClass(typeid<mytype>)
orTClass::GetClass(typeid<*mypointer>)
[quote]What’s the reason for so many base types? Is it historical? [/quote]Depends which one 
Some are historical, some are needed for implementation reason, some are logical needed.
[quote]Isn’t there any integer array type derived from TObject. I didn’t find one[/quote]No there is not.
[quote]
I just had a new look at the problem with the segmentation violation. I found out that this happens only when a file with not-TObject-derived-objects is opened in the object browser, whereas there’s no problem to load these objects in the CINT shell.[/quote]
This problem has been solved in the CVS repository (5.17/03)
Cheers,
Philippe