Set focus on Extjs textfield

Question

Currently I got problem with setting focus on extjs textfield. When form show, I want to set focus to First name text box and I try to use build in function focus() but stil

Answer 1

why not just add defaultFocus : '#first_name' instead of adding to much lines of code?

OR, after this.callParent(arguments); add this line Ext.getCmp('comp_id').focus('', 10);