Abbreviate acces to struct fields

Hello everyone,

i often need to acces a struct field like

sturcture.firstLevel.secondLevel.thirdLevel = 1

Now my question is: Is there a way to abbreviate this long code? Something like defining a pointer.

For example:

    sThird = pointer(sturcture.firstLevel.secondLevel.thirdLevel)

Whereas from now I could substitute

    sThird

for

    sturcture.firstLevel.secondLevel.thirdLevel

Is there a way to do this, so my code is to long?

Thank you for your time reading this.

Rafael

Answer 1

[Guillaume]

With structures, no it's not possible. Matlab does not support pointers/reference to variables. The workaround is to define a new variable, use that variable to do whatever you wanted to do, and then reassign that variable back to the structure

sThird = structure.firstLevel.secondLevel.thirdLevel;
%do something with sThird
structure.firstLevel.secondLevel.thirdLevel = sThird;

The only other way would be for the content of that thirdLevel field to be a handle class object that wrap whatever it is you store in there. In my opinion, this would be a waste of time just to offer shorter typing in the editor.

edit: forgot another option, which I also don't think is a good idea, use getfield and setfield:

field = {'firstlevel', 'secondlevel', 'thirdLevel'};
value = getfield(structure, field);
setfield(structure, field, someothervalue);

[Jan]

+1: The first suggestion is perfect. sThird = s.a.b.c creates a shared data copy in Matlab. This means if s.a.b.c is a struct and contains a huge array, the actual data are not duplicated. Therefore this method is fast, even faster than accessing s.a.b.c directly, when it occurres frequently in a loop:

structure.firstLevel.secondLevel.thirdLevel = 17;
tic
for k = 1:1e7
  structure.firstLevel.secondLevel.thirdLevel = ...
    structure.firstLevel.secondLevel.thirdLevel + m;
end
toc

structure.firstLevel.secondLevel.thirdLevel = 17;
tic
sub2 = structure.firstLevel.secondLevel;
for k = 1:1e7
  sub2.thirdLevel = sub2.thirdLevel + m;
end
toc

 Elapsed time is 0.053434 seconds.
 Elapsed time is 0.036151 seconds.

Well, does not look too impressive for 1e7 iterations.