The TRY Statement

The TRY...CATCH...FINALLY...END-TRY structure is the basis for structured exception handling. The TRY block allows you to test a section of code for exceptions that may occur during its execution. The CATCH block must specify the type of exception you wish to handle if one should occur during the execution of the TRY block. The FINALLY block allows you to execute a section of code following the TRY block, whether or not an exception occurred.

General Formats

Syntax Rules

Identifier-1 must be an object reference of class System.Exception or a subclass of System.Exception.

General Rules

If identifier-1 is omitted, it is equivalent to specifying the special register EXCEPTION-OBJECT as identifier-1. EXCEPTION-OBJECT has class System.Exception.
If an exception is raised during the execution of imperative-statement-1, each CATCH phrase is examined in the order specified until one is found for which the class of the exception that was thrown is equal to, or derives from, the class of identifier-1. If such an identifier-1 is found, identifier-1 is set to contain the value of the thrown exception, and the associated imperative-statement-2 is executed. Execution continues according to the rules for each statement specified in imperative-statement-2. If a control branching or conditional statement that causes explicit transfer of control is executed, control is transferred in accordance with the rules for that statement; otherwise, upon completion of the execution of imperative-statement-2, control is transferred to imperative-statement 3, if specified, or to the end of the TRY statement.
If no exception is raised during the execution of imperative-statement-1, execution continues according to the rules for each statement specified in imperative-statement-1. If a control branching or conditional statement that causes explicit transfer of control is executed, control is transferred in accordance with the rules for that statement; otherwise, upon completion of the execution of imperative-statement-1, control is transferred to imperative-statement 3, if specified, or to the end of the TRY statement.
Execution of imperative-statement-3 continues according to the rules for each statement specified in imperative-statement-3. If a control branching or conditional statement that causes explicit transfer of control is executed, control is transferred in accordance with the rules for that statement; otherwise, upon completion of the execution of imperative-statement-3, control is transferred to the end of the TRY statement

Example

The following is an example of specifying the EXCEPTION-OBJECT register:

           try
               set str to "some string"
           catch 
               display exception-object::ToString()
           finally
           end-try