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Technical Type Properties of Compatible Data Types The compatibility of two data types apart from reference types is based on the technical type properties of the data types. The technical type properties affect the following:
Whether data objects can be assigned directly or a type conversion has to take place.
The checking of the typing in assignments to field symbols or when assigning actual parameters to formal parameters. In addition, the compatibility of value assignments and comparisons between data objects apart from reference variables usually determines whether a conversion has to be performed or not. In the case of reference types with data objects (reference variables) that have a dynamic type apart from the static type, the term compatibility that is based entirely on technical type properties is not sufficient. ITOC
Latest notes: In order to check whether two data types are compatible at runtime, the method APPLIES_TO_DATA of RTTI class CL_ABAP_DATADESCR can be used. This can be helpful to prevent uncatchable exceptions when assigning generically typed data objects that are neither compatible nor convertible. For an example, see Assignment and Conversion Rules. NON_V5_HINTS ABAP_HINT_END
Non-Generic Data Types Except Reference Types Two non-generic data types apart from reference types and those that contain reference types as components are compatible if all their technical type properties match.
In the case of elementary data types, the technical type properties are as follows:
The built-in ABAP type
The length (for types c, n, p, and x)
The number of decimal places (for type p) With compatible elementary data types, all these properties match.
In the case of structured types , the technical type property is as follows:
The structure of components The structure of structured types not only refers to the sequence of elementary components in the memory, but also to the combination of components with substructures and whether a substructure is a boxed component. The names of the components and of the semantic properties defined in the ABAP Dictionary BEGIN_SECTION VERSION 5 OUT , such as conversion routines or documentation, END_SECTION VERSION 5 OUT however, are not important. With compatible structures, all components are compatible in pairs. This applies recursively down to the level of elementary data types. If two structures are constructed identically, but different substructures are declared as boxed components, the structures are not compatible.
In the case of table types, the technical type properties are as follows:
The line type
The table category
The table key including alias names With compatible internal tables, the line types are compatible and table category and table key match. Other properties, such as the initial memory requirement, are not important.
In the case of mesh types, the technical type properties are as follows:
The structure of nodes including the node names
The mesh associations of each component defined by ON conditions , including their names and the table key used
In the case of enumerated types , the technical type properties are as follows:
All properties of the enumerated type Each enumerated type is unique and only compatible with itself.
Latest notes:
The types listed here are not compatible with one another, for example, an elementary data type is never compatible with a structure, even if it has only one component.
The statement TYPES cannot be used to define different enumerated types with the same technical type properties. Even data types that are constructed with RTTC methods exactly like an existing enumerated type are not compatible with it. An enumerated type defined by direct or indirect reference (including RTTI) to an existing enumerated type, on the other hand, is compatible. NON_V5_HINTS ABAP_HINT_END
Generic Data Types A non-generic data type apart from a reference type is compatible with a generic data type if its technical properties are included in the generic data type.
Reference Types A reference type is the static type of reference variables that determines to which objects they can point. At runtime, reference var iables also have a dynamic type determined by the type of the object to which a reference variable points. The dynamic type can be more specific than the static type. For this reason, the rules for typing checks, assignments and comparisons cannot be covered by the idea of a compatibility that is based entirely on the technical properties of the static type. Instead, the following three points show how reference types can be used together:
When checking typing
A reference variable can be passed to a formal parameter typed as a reference variable if the type of the formal parameter is more general or equal to the type of the reference variable (known as an upcast) and the formal parameter cannot be changed within the procedure.
A reference variable can be assigned to a field symbol typed as a reference variable if the reference types are identical.
Assignments between reference variables are possible using an upcast or a downcast.
Data reference variables can be compared with all data reference variables and object reference variables can be compared to all object reference variables. As a rule, data reference variables can only be used with data reference variables and object reference variables only with object reference variables. No conversions take place between reference variables. Reference variables are either passed without conversion, assigned to each other, compared to each other, or not at all.
Latest notes:
These rules for the usability of reference variables in assignments introduced here are one-way. The type of a target reference variable, to which a source reference variable can be assigned, does not itself have to be assignable to the source reference variable. The usability of reference variables in comparisons on the other hand, is not directed.
If a reference variable is a component of a structure, the usability of the structure is determined accordingly. In particular, the usability of such a structure regarding assignments is also directed. NON_V5_HINTS ABAP_HINT_END
