Struct Dereference Operator (->)

Arguments

• StructVariable—variable or parameter of type struct which refers to one or more Structs
• MemberName—Struct member identifier; can be a literal name or a string; for example mem or "mem". An empty string "" returns Structs with no name.
• Function—Struct function. For more information, see ProcScript: Struct Functions.

Return Values

Returns an ordered collection of references to members of the Struct to which StructVariable refers.

If StructVariable refers to a collection of Structs rather than to a single Struct, the expression is evaluated for each Struct in the collection, and the resulting collections are combined into a single ordered collection of Structs.

If there are no members that satisfy the criteria, the result is NULL and an error is set in $procerror.

Use

Allowed in all components.

Description

The arrow -> is known as the dereference operator because the Struct being referred to changes (is de-referenced) from the one on the left to the one on the right. The dereference operator can be used multiple times in a statement to travers the nested levels of a Struct to get to the Struct member you need. For example, if you have a Struct referring to book that includes a Preface, you need to start from the top of the Struct nad use the dereference operator to get the Preface, and use it again to get the Acknowledgements section:

vStruct = Book->Preface->Acknowledgements

You can use the dereference operator to address Structs by name. By specifying an empty string (""), you can access nameless Structs. By using the * asterisk wildcard after the operator, you can get a collection of references to all members of a Struct.

Important: The * wildcard can only be used after the dereference operator. It cannot be used in constructs such as vStruct->c* to get all Structs whose names begin with c. ->* is actually a separate operator (the Struct collection operator).

Member Names as Strings

MemberName can be specified as a string, which means that it is possible to:

• Use string substitution to access a field name. For example, the following code returns the members with the name as specified in field F1.

  vStruct->"%%F1%%%" 

• Specify member names that include any character, including spaces, #, and $.

  vStruct->"first name"

• Address Struct members that have an empty string as name:

  vStruct->""

If a Struct has several members with the same name, you can access one of these members specifically, by using the dereference operator in combination with the struct index operator {N}. For example:

vBookStruct->chapter{2}