Class-based method call

Invokes a method of a class. If the method returns a value, the method call can appear anywhere that an expression can appear, and it can also appear as a single statement, ignoring the return value. If the method is VOID (does not return a value), the method call must appear as a single statement.

Syntax

[ { class-type-name | object-reference } : ]
  method-name ( [ parameter [ , parameter ] ... ] ) [ NO-ERROR ]
class-type-name
The name of an ABL or .NET class type that defines the specified method as a static member. The use of class-type-name to call a static method is optional when you call the method from within the class hierarchy where it is defined. For more information, see the notes for this reference entry. You cannot use class-type-name to call an instance method. For more information on specifying class (object) type names, see the Type-name syntax reference entry. You can use the unqualified class name with the presence of an appropriate USING statement.
object-reference
Specifies a reference to an ABL or .NET class instance (an object) that defines the specified method as an instance member. The use of object-reference to call an instance method is optional when you call the method from within the class hierarchy where it is defined. For more information, see the notes for this reference entry. You cannot use object-reference to call a static method. For information on specifying object references, see the reference entry for a Class-based object reference.
method-name
Specifies the name of an ABL or .NET class method you want to call. A class method is a named block of ABL or .NET code, similar to a procedure or user-defined function, that is defined in a class. An instance method is available for an instance of the class for as long as the class instance exists. A static method is available for the defining class type during the entire ABL session, regardless if an instance of the class exists. A class method is available inside or outside of the class hierarchy depending on its access mode.
( [ parameter [ , parameter ] ... ] )
Specifies zero or more parameters passed to the method. You must provide the parameters identified by the specified method, matched with respect to number, data type, and mode. To invoke a method that is overloaded in the class, you must specify sufficient information for each parameter in order to disambiguate methods that have similar parameter lists. Otherwise, the AVM raises an error identifying the ambiguity.

For more information on parameter passing syntax and on disambiguating overloaded ABL and .NET methods, see the Parameter passing syntax reference entry.

NO-ERROR
Suppresses ABL errors or error messages that would otherwise occur and diverts them to the ERROR-STATUS system handle. If an error occurs, the action of the statement is not done and execution continues with the next statement. If the statement fails, any persistent side-effects of the statement are backed out. If the statement includes an expression that contains other executable elements, like methods, the work performed by these elements may or may not be done, depending on the order the AVM resolves the expression elements and the occurrence of the error.

To check for errors after a statement that uses the NO-ERROR option:

  • Check the ERROR-STATUS:ERROR attribute to see if the AVM raised the ERROR condition.
  • Check if the ERROR-STATUS:NUM-MESSAGES attribute is greater than zero to see if the AVM generated error messages. ABL handle methods used in a block without a CATCH end block treat errors as warnings and do not raise ERROR, do not set the ERROR-STATUS:ERROR attribute, but do add messages to the ERROR-STATUS system handle. Therefore, this test is the better test for code using handle methods without CATCH end blocks. ABL handle methods used in a block with a CATCH end block raise ERROR and add messages to the error object generated by the AVM. In this case, the AVM does not update the ERROR-STATUS system handle.
  • Use ERROR-STATUS:GET-MESSAGE( message-num ) to retrieve a particular message, where message-num is 1 for the first message.

If the statement does not include the NO-ERROR option, you can use a CATCH end block to handle errors raised by the statement.

Some other important usage notes on the NO-ERROR option:

  • NO-ERROR does not suppress errors that raise the STOP or QUIT condition.
  • A CATCH statement, which introduces a CATCH end block, is analogous to a NO-ERROR option in that it also suppresses errors, but it does so for an entire block of code. It is different in that the error messages are contained in a class-based error object (generated by the AVM or explicitly thrown), as opposed to the ERROR-STATUS system handle. Also, if errors raised in the block are not handled by a compatible CATCH block, ON ERROR phrase, or UNDO statement, then the error is not suppressed, but handled with the default error processing for that block type.
  • When a statement contains the NO-ERROR option and resides in a block with a CATCH end block, the NO-ERROR option takes precedence over the CATCH block. That is, an error raised on the statement with the NO-ERROR option will not be handled by a compatible CATCH end block. The error is redirected to the ERROR-STATUS system handle as normal.
  • If an error object is thrown to a statement that includes the NO-ERROR option, then the information and messages in the error object will be used to set the ERROR-STATUS system handle. This interoperability feature is important for those integrating code that uses the traditional NO-ERROR technique with the newer, structured error handling that features error objects and CATCH end blocks.
  • To access more comprehensive error information for a .NET exception, use a CATCH end block instead of the NO-ERROR option. For more information on handling .NET exceptions, see the sections on .NET error handling in OpenEdge Development: GUI for .NET Programming.

Examples

The following code fragment shows a call to a public instance method (SetHighCustomerData( )) on an instance of the sample class, r-CustObj:

DEFINE VARIABLE rObj AS CLASS r-CustObj NO-UNDO.
rObj = NEW r-CustObj( ) NO-ERROR.

rObj:SetHighCustomerData( ) NO-ERROR.

This instance method initializes instance data for the class.

The following code fragment shows a call to a public static method (SetHighCustomerData( )) on the sample class type, r-CustObjStatic:

r-CustObjStatic:SetHighCustomerData( ) NO-ERROR.

This static method initializes class static data without having to instantiate the class, as in the previous instance code.

For more information on these methods and the sample classes in which they are defined, see the examples in the CLASS statement reference entry.

Notes

See also

Class-based object reference, METHOD statement, Parameter passing syntax, SUPER system reference, THIS-OBJECT system reference, Type-name syntax