# Copy a model

In this document we will learn how to create a copy of a xolotl model.

### Why you must use the copy method¶

Since xolotl objects derive from the handle class of MATLAB, they do not behave like normal variables. Specifically, you cannot copy them by making assignations:

% assuming x is a xolotl object
x2 = x; % x2 and x are actually the same thing


and changes in x2 will automatically change x and vice versa.

Furthermore, xolotl will throw an error if you have created models with identical structure but different compartment names. If you need to instantiate two models simultaneously that are identical in their component structure, you should copy the model.

Therefore, if you want to make a true copy of a xolotl object, you must use its copy method:

x2 = copy(x);