Constructor Operators for Constructor Expressions

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Syntax

Effect

A constructor expression consists of the following:

A built-in constructor operator

A data type or object type type that matches the operator and that can be derived implicitly from the operand position using #

Type-specific 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 reference operator REF is used to construct a data reference to a data object in operand positions or to control the results of table expressions. The result is a data reference variable.

The component operator CORRESPONDING is used to construct a structure or an internal table in 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 in a parameter using a mapping rule.

The lossless operator EXACT is used to create a value in an operand position without losing data. The result is a data object of the specified type, derived from a lossless assignment or a lossless calculation.

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.

Data types and classes that are visible and usable in the current operand position can be specified for type. This includes the built-in ABAP types, 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 the operand type is not unique and is not known completely, a type inference is performed to determine a data type. This is described in each constructor expression.

LET expressions can be used to define local helper 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.

Unlike method chainings or table expressions, constructor expressions cannot be placed on the left side of a structure component selector, since constructing a structure just to access a single component is pointless.

If a data type from ABAP Dictionary is used for the type, the result of a constructor is given its semantic attributes.

Example

Fills an internal table itab with the value operator VALUE. The data type is inferred from the left side of the assignment.

DATA itab TYPE TABLE OF i WITH EMPTY KEY.

itab = VALUE #( ( 1 ) ( 2 ) ( 3 ) ).