The TAG_NAMES function returns a string array containing the names of the tags in a structure expression. It can also be used to determine the expression’s structure name (if the structure has a name).
Although an instance of an object class has an associated structure definition, it is not generally possible to inspect the tags defined by the class structure directly using TAG_NAMES. The exception to this rule is that inside an object method you can use TAG_NAMES to inspect the class structure of an object reference.
Print the names of the tags in the system variable !P by entering:
PRINT, TAG_NAMES(!P)
IDL prints:
BACKGROUND CHARSIZE CHARTHICK CLIP COLOR FONT LINESTYLE MULTI
NOCLIP NOERASE NSUM POSITION PSYM REGION SUBTITLE SYMSIZE T
T3D THICK TITLE TICKLEN CHANNEL
Print the name of the structure in the system variable !P:
PRINT, TAG_NAMES(!P, /STRUCTURE_NAME)
IDL prints:
!PLT
Result = TAG_NAMES( Expression [, /STRUCTURE_NAME] )
Returns structure tag names or the expression’s structure name.
The structure expression for which the tag names are returned. This argument must be of structure type. TAG_NAMES does not search for tags recursively, so if Expression is a structure containing nested structures, only the names of tags in the outermost structure are returned.
Set this keyword to return a scalar string that contains the name of the structure instead of the names of the tags in the structure. If the structure is “anonymous”, an empty string is returned.
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