def djangofield_to_extjs_xtype(djangofield, foreignkey_restfulcls):
    if isinstance(djangofield, ForeignKey):
        return restfulcls_to_extjscombobox_xtype(foreignkey_restfulcls)
    elif isinstance(djangofield, fields.DateTimeField):
        return restfulcls_to_datepicker_xtype()
    elif isinstance(djangofield, fields.BooleanField):
        return "xtype: 'checkbox'"
    else:
        return "xtype: 'textfield'"
def djangofield_to_extjs_xtype(djangofield, foreignkey_restfulcls):
    if isinstance(djangofield, ForeignKey):
        if foreignkey_restfulcls == None:
            raise ValueError('Foreign key: {fieldname} has no foreignkey_restfulcls. '
                             'This is usually defined in Meta.foreignkey_fields in '
                             'the ModelRestfulView.'.format(fieldname=djangofield.name))
        return restfulcls_to_extjscombobox_xtype(foreignkey_restfulcls)
    elif isinstance(djangofield, fields.DateTimeField):
        return restfulcls_to_datepicker_xtype()
    elif isinstance(djangofield, fields.BooleanField):
        return "xtype: 'checkbox'"
    else:
        return "xtype: 'textfield'"