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This is documentation for Caché & Ensemble. See the InterSystems IRIS version of this content.

For information on migrating to InterSystems IRIS, see the InterSystems IRIS Migration Guide and Migrating to InterSystems IRIS, both available on the WRC Distributions page (login required).

THROW

Throws an exception from a TRY block to a CATCH exception handler.

Synopsis

THROW [oref]

Arguments

oref Optional — A user-defined object reference.

Description

The THROW statement explicitly issues an exception from within a block of code defined by a TRY statement. Issuing a THROW transfers execution from the TRY block to the corresponding CATCH exception handler.

THROW is used to issue an explicit exception. MVBasic issues an implicit exception when a runtime exception occurs. A runtime exception generates an exception object which it throws to a CATCH exception handler.

THROW has two forms:

  • Without an argument

  • With an argument

THROW without an Argument

Argumentless THROW transfers exception processing to the corresponding CATCH exception handler. No object is pushed on the stack, but the %New() method is called.

THROW with an Argument

THROW oref specifies a user-defined object reference, which it throws to the CATCH statement.

Arguments

expression

A user-defined object reference (oref). For example, THROW "Sample.MyException"->%New("Example Error",45). The creation and population of this exception object is the responsibility of the programmer.

Examples

The following example shows the use of THROW:

  TRY
    PRINT "about to issue a THROW statement"
    THROW "Sample.MyException"->%New("Example Error",45,"Sample Program")
    PRINT "this should not display"
  CATCH myvar 
    PRINT "this is the exception handler"
    PRINT :myvar->Name,"Error Name"
    PRINT :myvar->Code,"Error Code Number"
    PRINT :myvar->Location,"Error Location"
  END TRY
  PRINT "this is where the code falls through"
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See Also

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