code: function(readOnly) {
          var me = this,
              inputEl = me.inputEl;
          readOnly = !!readOnly;
          me[readOnly ? 'addCls' : 'removeCls'](me.readOnlyCls);
          me.readOnly = readOnly;
          if (inputEl) {
              inputEl.dom.readOnly = readOnly;
          } else if (me.rendering) {
              me.setReadOnlyOnBoxReady = true;
          }
          me.fireEvent('writeablechange', me, readOnly);
      }
docs: Sets the read only state of this field.
  @param {Boolean} readOnly Whether the field should be read only.