Unable to edit an ALV in WDA

I have a requirement to make the column of an ALV editable in WDA.

I have used the following code in the method WDDOINIT of the result view where ALV needs to be displayed.

But it resulted in a dump.

Can anyone help me on this??

method WDDOINIT .

data: l_value TYPE REF TO cl_salv_wd_config_table,
lr_column TYPE REF TO cl_salv_wd_column.

DATA: lr_column_settings TYPE REF TO if_salv_wd_column_settings,
lr_input_field TYPE REF TO cl_salv_wd_uie_input_field.
lr_column_settings ?= l_value.
lr_column = lr_column_settings->get_column( 'CARRNAME' ).
CREATE OBJECT lr_input_field
EXPORTING
value_fieldname = 'CARRNAME'.
lr_column->set_cell_editor( lr_input_field ).

endmethod.