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Runtime Errors When Accessing Data Objects

Other versions: 7.31 | 7.40 | 7.54

Background

Using data objects can cause runtime errors if the data object contains unsuitable content or the access to the data object is unsuitable. Examples:

• Assigning values outside the value range of a target variable

• Using values that cannot be converted to the required type. In other words, a conversion rule exists but the source field content is not convertible. For example, you are trying to assign a character field (with content that cannot be interpreted as a number) to a numeric field.

• Access to parts of data objects (subfield access). Either offset access/length access or the use of predefined subfunctions such as substring.

Rule

Preventing Runtime Errors When Accessing Data Objects

You need to prevent runtime errors that can occur when accessing data objects. Robust applications should always be programmed to avoid these errors.

Details

If it not possible to determine by filling data objects appropriately whether subsequent access causes errors, then either the relevant properties must be checked before data access or possible exceptions (subclasses of CX_SY_CONVERSION_ERROR or CX_SY_DATA_ACCESS_ERROR) must be caught during data access.

Bad Example

The following source code illustrates a typical situation that can easily cause a runtime error if the subarea defined by offset and length is not defined in text.

DATA text TYPE string.
...
substring = text+offset(length).
...

Good Example

The following two source codes illustrate how the above example can be changed to avoid runtime errors using prevention or exception handling.

IF strlen( text ) > offset + length.
  substring = text+offset(length).
ELSE.
  ...
ENDIF.

TRY.
  substring = text+offset(length).
CATCH cx_sy_range_out_of_bounds.
   ...
ENDTRY.