Type conversion

The type conversion operator creates a property that converts an object of one built-in class to an object of another built-in class. The result belongs to the target built-in class. If type conversion is not possible, the property value will be NULL.

Supported conversions

Which conversions are meaningful depends on the built-in class families of the source and target classes:

• Within the family of numbers, the value is kept as far as the target class allows; when the value does not fit in the target class, the result is NULL.
• Between numbers and strings, the value is converted between its numeric and textual forms; when the source string cannot be read as a number of the target class, the result is NULL.
• Strings also convert to and from the JSON, JSONTEXT, XML, and HTML classes.

String and file types

String types can be converted to human-readable file types (CSVFILE, XMLFILE, JSONFILE, HTMLFILE, etc.), and vice versa - human-readable file types can be converted to string types. A file of a specific type can also be converted to a file of dynamic type (FILE, NAMEDFILE) and back, keeping the file content; the dynamic-type file additionally carries the extension, and NAMEDFILE also the name.

info

Converting dynamic-type files (FILE) to strings and vice versa is prohibited in the current implementation, but if necessary this can be done via an intermediate human-readable type - for example, by first converting to CSVFILE, and only then to FILE (the resulting file will have the extension CSV)

Implicit conversions

Apart from the explicit conversion operator, the platform converts a value to another class implicitly in several contexts, without any conversion written by the developer:

• When values of different but compatible classes are combined — by addition or subtraction (see the arithmetic operators), by the selection operators, or by the extremum operators — each value is converted to their common ancestor, which becomes the result class; in particular, the number classes widen this way (an INTEGER combined with a NUMERIC becomes that NUMERIC).
• In string concatenation, an operand that is not a string is converted to a string.
• When a value is written to a property of a different but compatible class, it is converted to that class.
• A file of a specific type is converted to a file of dynamic type (FILE, NAMEDFILE) implicitly — for example during data import without a specified format, or when working with an external system; the resulting extension is determined as for the explicit conversion.

Language

To implement conversion, the type conversion operator is used.

Examples

itemCount = DATA INTEGER (Store);
itemCountToString(s) = BPSTRING[10](itemCount(s));

barcode = DATA STRING[15] (Item);
longBarcode(Item i) = LONG(barcode(i));