IDL operation declarations: context expression

For an overview of the Interface Declarations Language (IDL) operation declarations, see "IDL operation declarations".

The optional context expression (context-expr) in an operation declaration indicates which elements of the caller's context the operation's implementation can consult. A context expression is specified as follows:

context ( identifier1, identifier2, ... )

where each identifier is a string literal made up of alphanumeric characters, periods, underscores and asterisks. The first character must be alphabetic and an asterisk can only appear as the last character, where it serves as a wildcard matching any characters. If convenient, identifiers can consist of period-separated , valid identifier names, but that form is optional.

The context is a special object that is specified by the CORBA standard. It contains a property list. The property list contains a set of property name and string value pairs that the caller can use to store information about its environment, which operations can find useful. It is used similar to environment variables. The property list is passed as an additional parameter to operations that are defined as context-sensitive in the IDL.

The context expression of an operation declaration in IDL specifies which property names the operation uses. If these properties are present in the context object supplied by the caller, they are passed to the object implementation, which can access them through the interface of the context object.

The argument that is passed to the operation having a context expression is a Context object, not the names of the properties. The caller must create a context object and use its interface to set the context properties. The caller then passes the context object in the operation invocation. The CORBA standard allows properties, in addition to those in the context expression, to be passed in the context object.


Related reference
IDL operation declarations



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