ABAP New Syntax Lecture 2: VALUE, NEW, CONV, CAST and REF

Constructor expressions let you create values, objects, conversions and references directly where a result is required. In this lecture we will use VALUE, NEW, CONV, CAST and REF with practical ABAP examples.

Learning outcome: You will know what each operator returns, when # can infer a type, and when an explicit type improves safety and readability.

1. What is a constructor expression?

A constructor expression uses an operator plus a type and parentheses. Its result can be used on the right side of an assignment, as a method parameter or inside another expression.

DATA(result) = operator type( parameters ).

The placeholder # asks the compiler to derive the operand type from the surrounding context. Use it only when that context is unambiguous.

2. VALUE — construct structures and internal tables

VALUE creates a data value. It is especially useful for structures, ranges and internal tables because initialization stays close to the declaration.

TYPES: BEGIN OF ty_item,
         id   TYPE i,
         text TYPE string,
       END OF ty_item,
       ty_items TYPE STANDARD TABLE OF ty_item WITH EMPTY KEY.

DATA(ls_item) = VALUE ty_item(
  id   = 100
  text = 'Demo' ).

DATA(lt_items) = VALUE ty_items(
  ( id = 100 text = 'Demo' )
  ( id = 200 text = 'Practice' ) ).

BASE keeps existing rows

lt_items = VALUE #(
  BASE lt_items
  ( id = 300 text = 'Added with BASE' ) ).

BASE copies the starting value before the new components or rows are applied. Without it, you construct a fresh value.

3. NEW — create objects and anonymous data

NEW returns a reference. With a class it creates an object; with a data type it creates an anonymous data object.

DATA(lo_service) = NEW zcl_service(
  iv_mode = 'TEST' ).

DATA(lr_count) = NEW i( 10 ).
lr_count->* = lr_count->* + 1.

VALUE vs NEW: VALUE returns a data value, while NEW returns a reference to the created object or data object.

4. CONV — explicit data conversion

CONV converts one value to the requested data type. It is clearer than depending on an implicit conversion when the target type affects the result.

DATA(lv_number) = CONV i( '42' ).
DATA(lv_text)   = CONV string( lv_number ).

DATA(lv_ratio) = CONV decfloat34( 7 ) /
                 CONV decfloat34( 3 ).

Conversions can fail or lose information depending on the types and values involved. Validate external input before converting it.

5. CAST — change the static reference type

CAST works with references. A downcast should only be performed when the referenced object is compatible with the target class or interface.

IF lo_object IS INSTANCE OF zcl_child.
  DATA(lo_child) = CAST zcl_child( lo_object ).
  lo_child->run_child_logic( ).
ENDIF.

CONV converts data values; CAST changes the static type through which an existing reference is accessed.

6. REF — create a data reference

DATA(lv_total) = 1250.
DATA(lr_total) = REF #( lv_total ).

lr_total->* = 1500.
" lv_total is now 1500

7. Choosing the correct operator

Operator	Use	Returns
VALUE	Construct a value	Data object
NEW	Create object or anonymous data	Reference
CONV	Convert a data value	Converted value
CAST	Cast an existing reference	Typed reference
REF	Reference an existing data object	Data reference

8. Common mistakes

• Using # where the compiler has no clear target type.
• Using CAST without checking whether a downcast is valid.
• Hiding important conversions in a very long nested expression.
• Assuming NEW returns a value instead of a reference.
• Replacing readable intermediate variables only to make the code shorter.

9. Practice exercises

1. Create a structure and a three-row internal table with VALUE.
2. Append one row while preserving existing rows with BASE.
3. Create an anonymous integer with NEW i( ) and change its dereferenced value.
4. Convert character input to i with suitable error handling.
5. Explain the difference between NEW and REF in your own words.

10. Interview quick checks

Does VALUE create a reference?

No. It constructs a data value. Use NEW when the required result is a reference to a newly created object or anonymous data object.

What does # mean?

It requests type inference from the operand position. It is useful only when the required type is known from the surrounding context.

Are CONV and CAST interchangeable?

No. CONV performs a data conversion, whereas CAST works with reference typing.

Official SAP references

• Constructor expressions — ABAP Keyword Documentation
• Creating objects and values — SAP Help
• NEW instance operator — ABAP Keyword Documentation

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Examples are educational. Verify syntax availability, released APIs and data types in the ABAP Keyword Documentation for your target system.