ref_descr ?= cl_abap_typedescr=>describe_by_name explanation

[Former Member]

Hello Everyone,

Can somebody explain what is happening

in this part of the code. Below the complete code.

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ref_descr ?= cl_abap_typedescr=>describe_by_name( p_table ).

it_details[] = ref_descr->components[].

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One more request, what are these structures

abap_compdescr_tab, abap_compdescr, cl_abap_structdescr, lvc_s_fcat are these tables? Please kindly let me know

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data : it_details type abap_compdescr_tab,

wa_details type abap_compdescr.

data : ref_descr type ref to cl_abap_structdescr.

data: new_table type ref to data,

new_line type ref to data,

wa_it_fldcat type lvc_s_fcat.

ref_descr ?= cl_abap_typedescr=>describe_by_name( p_table ).

it_details[] = ref_descr->components[].

loop at it_details into wa_details.

clear wa_it_fldcat.

if wa_details-name = 'TIMESTMP'.

wa_it_fldcat-fieldname = wa_details-name.

wa_it_fldcat-datatype = wa_details-type_kind.

wa_it_fldcat-inttype = wa_details-type_kind.

wa_it_fldcat-intlen = r.

wa_it_fldcat-decimals = wa_details-decimals.

append wa_it_fldcat to it_fldcat.

append wa_it_fldcat-fieldname to it1.

else.

wa_it_fldcat-fieldname = wa_details-name.

wa_it_fldcat-datatype = wa_details-type_kind.

wa_it_fldcat-inttype = wa_details-type_kind.

wa_it_fldcat-intlen = wa_details-length.

wa_it_fldcat-decimals = wa_details-decimals.

append wa_it_fldcat to it_fldcat.

append wa_it_fldcat-fieldname to it1.

endif.

endloop.

Thanks

Krishna

[uwe_schieferstein]

Hello Krishna

The static method cl_abap_typedescr=>describe_by_name returns an instance of type CL_ABAP_TYPEDESCR.

This class is a superclass of CL_ABAP_STRUCTDESCR (the inheritance hierarchy is:

CL_ABAP_TYPEDESCR -> CL_ABAP_DATADESCR -> CL_ABAP_COMPLEXDESCR -> CL_ABAP_STRUCTDESCR).

In the statement

ref_descr ?= cl_abap_typedescr=>describe_by_name( p_table ).
it_details[] = ref_descr->components[].

we have a widening cast ('?=') from CL_ABAP_TYPEDESCR (returned value) to CL_ABAP_STRUCTDESCR (descr_ref variable).

Now <i>p_table</i> represents a structure (like 'SFLIGHT'). The components of this structure, i.e. the table fields, are found in the public attribute ref_descr->components.

Please note that it is unnecessary to write

ref_descr->components<b>[]</b>

because in ABAP-OO it is not allowed to use itabs with header lines but exclusively table types.

The other classes (like cl_abap_typedescr, cl_abap_compdescr) are used to get the runtime type information (RTTI) of different DDIC objects.

Regards

Uwe