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ABAP Keyword Documentation →  ABAP - Reference →  Predefined Types, Data Objects, Functions, and Constructors 

Constructor Operators for Constructor Expressions

Other versions: 7.31 | 7.40 | 7.54

Syntax


... NEW|
VALUE|
CONV|
CORRESPONDING|
CAST|
REF|
EXACT|
REDUCE|
FILTER|
COND|SWITCH 
     type( ... ) ...

Effect

A constructor expression consists of a

  • a data type or object type type that matches the operator and that can be derived implicitly from the operand position using #,
  • and type-specified parameters specified in parentheses.

Each constructor expression creates a result whose data type is determined using the specified type. The parameters specified in parentheses are used to pass input values. The following constructor operators exist:

  • The instance operator NEW is used to create objects in operand positions. The result is a reference variable of the static type type that points to the new object. The input values determine the content of the new object.
  • The value operator VALUE is used to fill complex data objects with values in operand positions, create initial values of any data type, or control the results of table expressions. The result is a data object of the specified type type. The input values determine the content of the result.
  • The conversion operator CONV is used for conversions between data types in operand positions. The result is a data object of the specified type type produced by the conversion from an input value.
  • The casting operator CAST is used for down casts of reference variables in operand positions. The result is a reference variable of the static type type produced by the assignment from an input value.
  • The component operator CORRESPONDING is used to build a structure or an internal table at an operand position. The result is a structure or internal table, whose components are filled with values from identically named components or from argument components specified using a mapping rule.
  • The reduction operator REDUCE constructs a value from condition iterations or from table iterations.
  • The filter operator FILTER constructs an internal table by filtering the rows of an internal table.
  • The conditional operators COND and SWITCH are used to create values or raise class-based exceptions in operand positions in accordance with conditions. The result is determined by logical expressions or by a case distinction.

A constructor expression can be specified in general expression positions and functional positions with an appropriate operand type. The result is used here as an operand. In a calculation expression or relational expression, the specified type type is incorporated into the calculation type or comparison type. An expression with the operator VALUE that is not used to create an initial value cannot be specified directly in an arithmetic expression. This is because it never matches the operand type here. Expressions with the operators NEW and CAST can be positioned directly before the object component selector -> and can occur in chainings.

Visible, usable data types and classes can be specified for type in the current position. This includes predefined ABAP type, types defined using TYPES, types from ABAP Dictionary, and both local and global classes.

If the data type required in an operand position is unique and fully recognizable, the # character can be used instead of an explicitly specified type type and the operand type is used. If REF is used, # can be specified for non-unique operand types as well. In the case of EXACT, the operand type can also be generic.

LET expressions can be used to define local help fields in all suitable constructor expressions.


Notes

  • Constructor operators can be classified as follows:

  • Constructor operators like NEW and VALUE construct new values whose parts can be passed (except when the initial value is created), whereas constructor operators like CONV, CAST, REF and EXACT convert a single passed value.

  • Constructor operators like NEW, CAST, and REF always return reference variables, whereas constructor operators like VALUE, CONV, and EXACT return all types of data objects.