Convert Integer to String

[Anonymous]

I need to convert a primary key Interger to a String.
In the tMap I have written: (REF.REF_ID).toString() but the following error appears: "cannot invoke toString() on the primitive type int".
How can I convert it?
Thanks

[Anonymous]

I'm new to Talend.  what do you mean by REF.REF_ID.  Would  you provide an example. Also there is a DataOperation Function called CHAR(int I):id_Character - DataOperation which converts a numeric value to its ASCII character string equivalent.  Does this accomplish the same thing?

[Anonymous]

BTW, the CHAR function is listed in tMAP if using the Expression Builder.