Caché Basic Reference
Throw
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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 command explicitly issues an exception from within a block of code defined by a Try command. Issuing a Throw transfers execution from the Try block to the corresponding Catch exception handler.
Throw is used to issue an explicit exception. Caché issues an implicit exception when a runtime error occurs. A runtime error generates an exception object which it throws to a Catch exception handler.
Throw has two forms:
Throw without an Argument
Argumentless Throw transfers error processing to the corresponding Catch error 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 command, pushing it on the execution stack. The calling of the %New() method is optional.
Arguments
expression
A user-defined object reference (oref). For example, Throw ##class(%Exception).%New(). The creation and population of this exception object is the responsibility of the programmer.
Examples
The following example shows an argumentless Throw:
  Try
    SET x=2
    PRINTLN "about to divide by ",x
  Throw
    SET a=7/x
    PRINTLN "Success: the result is ",a
  Catch myvar 
    PRINTLN "this is the exception handler"
    PRINTLN "Error number: ",Err.Number
    PRINTLN "Error is: ",Err.Description
    PRINTLN "Error code: ",myvar.Code
  END Try
  PRINTLN "this is where the code falls through"
 
See Also