Default Coercion Handlers (original) (raw)

This appendix lists the type conversions performed by the default coercion handlers provided by the Mac OS. These handlers may be implemented by the Apple Event Manager, the Open Scripting framework, or other frameworks.

Support for the following coercions was added in Mac OS X version 10.4:

Between these types:
typeStyledText, typeUnicodeText, typeUTF8Text, and typeUTF16ExternalRepresentation
and these types:
typeType, typeEnumerated, and the numeric types typeSInt16, typeSInt32, typeUInt32, typeSInt64, typeIEEE32BitFloatingPoint, typeIEEE64BitFloatingPoint, and typeExtended.
See table Table C-1 for a mapping between the preferred and non-preferred numeric constant names.
From typeChar to typeStyledText.

Coercion Handler Tables

Table C-1 shows some older, non-preferred numeric constant names and their preferred equivalents. To find available coercions for a non-preferred name from Table C-1, look up its equivalent preferred name in Table C-2.

Table C-1 Older, non-preferred numeric types and their preferred types

Non-preferred numeric constant name	Preferred numeric constant name
typeSMInt, typeShortInteger	typeSInt16
typeInteger, typeLongInteger	typeSInt32
typeMagnitude	typeUInt32
typeComp	typeSInt64
typeSMFloat, typeShortFloat	typeIEEE32BitFloatingPoint
typeFloat, typeLongFloat	typeIEEE64BitFloatingPoint

Table C-2 lists the default coercions handled by the Apple Event Manager.

Table C-2 Default coercions provided by the Apple Event Manager

Coerce from descriptor type	To descriptor type	Comment
typeChartypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	typeSInt16typeSInt32typeSInt64typeIEEE32BitFloatingPointtypeIEEE64BitFloatingPointtypeExtended	Any string that is a valid representation of a number can be coerced into an equivalent numeric value.
typeSInt16typeSInt32typeSInt64typeIEEE32BitFloatingPointtypeIEEE64BitFloatingPointtypeExtended	typeChartypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	Any numeric descriptor type can be coerced into the equivalent text string.
typeSInt16typeSInt32typeSInt64typeIEEE32BitFloatingPointtypeIEEE64BitFloatingPointtypeExtended	typeSInt16typeSInt32typeSInt64typeIEEE32BitFloatingPointtypeIEEE64BitFloatingPointtypeExtended	Any numeric descriptor type can be coerced into any other numeric descriptor type.
typeChartypeIntlTexttypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	typeChartypeIntlTexttypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	If the destination encoding cannot represent a character in the source text, the result is undefined.
typeChartypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	typeTypetypeEnumeratedtypeKeywordtypeProperty	Any four-character string can be coerced to one of these descriptor types.
typeEnumeratedtypeKeywordtypePropertytypeType	typeChartypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	Any of these descriptor types can be coerced to the equivalent text string.
typeIntlText	typeChartypeStyledTexttypeUnicodeTexttypeUTF8TexttypeUTF16ExternalRepresentation	The result contains text only, without the script code or language code from the original descriptor.
typeTrue	typeBoolean	The result is the Boolean value true.
typeFalse	typeBoolean	The result is the Boolean value false.
typeEnumerated	typeBoolean	The enumerated value 'true' becomes the Boolean value true. The enumerated value 'fals' becomes the Boolean value false.
typeBoolean	typeEnumerated	The Boolean value false becomes the enumerated value 'fals'. The Boolean value true becomes the enumerated value 'true'.
typeSInt16	typeBoolean	A value of 1 becomes the Boolean value true. A value of 0 becomes the Boolean value false.
typeBoolean	typeSInt16	A value of false becomes 0. A value of true becomes 1.
typeAlias	typeFSS	An alias is coerced into a file system specification. Not recommended—use typeFSRef instead.
typeAlias	typeFSRef	An alias is coerced into a file system reference.
typeAppleEvent	typeAppParameters	An Apple event is coerced into a list of application parameters for the LaunchParamBlockRec parameter block.
any descriptor type	typeAEList	A descriptor is coerced into a descriptor list containing a single item.
typeAEList	type of list item	A descriptor list containing a single descriptor is coerced into a descriptor.