Assignment (=) statement

Assigns the value of an expression to a database field or variable.

Data movement

 

Syntax 

 

field = expression [ NO-ERROR ]

field

The name of an ABL data element to which you want to assign the value of expression and that is defined with a data type that is compatible with the data type of expression. This data element can include a:

Database or temp-table field

Variable scoped to the current procedure, user-defined function, or method of a class or an accessible class-based variable data member, including a subscripted or unsubscripted array variable

Parameter defined for the current procedure, user-defined function, or method of a class, including a subscripted or unsubscripted array parameter

Writable class-based or COM property, including a subscripted or unsubscripted array property

Writable handle attribute (such as PRIVATE-DATA)

Writable system handle (such as CURRENT-WINDOW)

ABL syntax that specifies a keyword-driven assignment statement (such as the PROPATH statement, SUBSTRING statement, or similar statement)

expression

An expression with a data type that is consistent with the data type of field. For more information, see the Expression 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.

For the Assignment (=) statement with NO-ERROR, if ERROR is raised, then the leftside of the assignment will be unchanged.

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.

Example 

This procedure resets all the monthly quota values to 2500 in all salesrep records. If you want to set values for individual array elements, you can do so by making an explicit assignment using the assignment statement and a specific array reference, such as month-quota[1] or month-quota[i].

 

r-asgmnt.p

DEFINE VARIABLE ctr AS INTEGER NO-UNDO.   FOR EACH SalesRep: DO ctr = 1 TO 12: SalesRep.MonthQuota[ctr] = 2500. END. END.

Notes 

If field is an integer and expression is a decimal, the AVM rounds the value of the expression before assigning it. If field is a decimal and expression is a decimal, the AVM rounds the value of the expression to the number of decimal places defined for the field in the Data Dictionary, or defined or implied for a variable or temp-table field.

If field is an ABL array type (defined with EXTENT) and expression is not an array, and you do not identify a particular array element, the AVM stores expression in each element of the array. If you identify a particular element, the AVM stores expression in the specified array element.

If both field and expression are ABL array types, the AVM copies the data for all expression array elements into the corresponding elements of the field array. This is known as a deep copy.

An indeterminate array is one where the size of the EXTENT is not yet fixed. A determinate array is one where the EXTENT size is fixed. When deep copying one array to another, the following rules apply:

If both the array on the left-hand side and the right-hand side of the equation are determinate arrays, the EXTENT size must match or the AVM raises an error.

You cannot assign an indeterminate array to a determinate array.

You can assign any array to an indeterminate array, but you cannot assign a scalar value to an indeterminate array.

ABL allows you to assign ABL arrays and .NET array objects to each other. How an array assignment works between ABL and .NET arrays depends upon the array type of field (the target of the assignment) and the array type of expression (the source for the assignment). For more information, see the Data types reference entry.

If expression is an ABL handle-based object (for example, a temp-table, ProDataSet, widget, or socket), field must be a temp-table field, variable, or other ABL data element defined as a compatible handle. In this case, the AVM assigns only the handle of the ABL handle-based object to field, not the entire object and its contents.

If you assign a value to a database field, any ASSIGN trigger associated with that field executes at the end of the assignment statement (after any index changes are made). If the trigger raises ERROR, the assignment fails and the database changes are undone.

You can embed an assignment in a SET or UPDATE statement.

For multiple assignments, use the ASSIGN statement. This is more efficient than multiple assignment statements.

If field is a handle, the expression on the right-hand-side must also evaluate to a handle value that is specified using an appropriate reference to a handle-based object handle. For more information on object handle references, see the “Handle Attributes and Methods Reference” section.

You can assign DATE, DATETIME, and DATETIME-TZ data. When the data type expression on the left side of the assignment statement contains more information than the data type expression on the right side provides (for example, datetime-tz = date where a DATETIME-TZ value contains more information than a DATE value), the time value defaults to midnight and the time zone value defaults to the session's time zone. When the data type expression on the left side of the assignment statement contains less information than the data type expression on the right side provides (for example, date = datetime-tz where a DATE value contains less information than a DATETIME-TZ value), the AVM converts the DATETIME-TZ value to the local date and time of the session, then drops the time and time zone.

Starting with Version 9.1, you can assign RAW values to MEMPTR variables and MEMPTR values to RAW variables. If the target variable is a RAW data type, the AVM re-sizes the target variable, if necessary, so that after the assignment is the same size as the source. Note that after the assignment (whether RAW = MEMPTR or MEMPTR = RAW), the target variable has a copy of the memory associated with the source—each variable has an independent copy of the data.

You can assign large object data from one BLOB or MEMPTR to another, and from one CLOB, LONGCHAR, or CHARACTER to another. You cannot assign large object data between BLOBs and CLOBs or MEMPTRs and LONGCHARs. You can accomplish this, indirectly, by using the COPY-LOB statement. For more information, see the COPY-LOB statement reference entry.

Note:

When assigning BLOB or CLOB fields, the field must appear by itself on either the right-hand or the left-hand side of the assignment.

Table 8 lists the default character conversions that the AVM performs when assigning CLOB, LONGCHAR, and CHARACTER data between a source and target object. References to CLOBCP and CLOBDB represent CLOB data in either the CLOB’s defined code page or the database's defined code page, respectively. References to the "fixed code page" represent the code page of a target LONGCHAR variable set using the FIX-CODEPAGE statement.

 

Table 8:

Default assignment character conversions

When the target object (on the left) is a . . .	And the source object (on the right) is a . . .	The AVM converts the data in the source object to . . .
LONGCHAR	CLOBDB	-cpinternal or the fixed code page
LONGCHAR	CLOBCP	The CLOB’s defined code page or the fixed code page
LONGCHAR	CHARACTER	-cpinternal or the fixed code page
CLOBDB	CHARACTER	The database's defined code page
CLOBDB	LONGCHAR	The database's defined code page
CLOBCP	CHARACTER	The CLOB’s defined code page
CLOBCP	LONGCHAR	The CLOB’s defined code page
CHARACTER	CLOBDB	-cpinternal code page
CHARACTER	CLOBCP	-cpinternal code page
CHARACTER	LONGCHAR	-cpinternal code page

When you assign the Unknown value (?) to a BLOB or CLOB field, the AVM deletes any associated object data.

If expression is a solitary invocation of the NEW function (classes), this statement represents and conforms to the rules specified for the NEW statement.

If expression evaluates to an object reference value, field must also be a data element defined as a class or interface type that is type-compatible with expression according to the rules for assigning references to class instances defined for the NEW statement. For more information, see the NEW statement reference entry. Thus, you can assign one object reference variable to another object reference variable when the destination object reference (on the left side of the assignment) is defined for the same class, a super class, or an interface of the object reference being assigned (on the right side of the assignment). The destination object reference retains its defined class or interface type for compilation. However, following its assignment, at run time, the destination represents the sublcass of field (or the class that implements the interface specified by field) that is defined by expression.

If field has a class type that is a subclass lower in the class hierarchy than the class type represented by expression, you can cast expression to the type of field using the CAST function, but only if expression is a super class that actually contains an instance of the field class type. If field has a class type that implements an interface type represented by expression, you can similarly cast expression using the CAST function, but only if expression actually contains an instance of the field class type. For more information about the CAST function, see the CAST function reference entry.

After the assignment, field contains a copy of the object reference value returned by expression, which points to the same object instance, not a copy of the object referenced by expression.

Although you can assign an object reference to a temp-table field defined as a Progress.Lang.Object class type, you cannot assign an object reference to a field in a database table. For more information, see OpenEdge Development: Object-oriented Programming.

See also 

ASSIGN statement, CAST function, Class-based object reference, COPY-DATASET( ) method, COPY-LOB statement, COPY-TEMP-TABLE( ) method, Data types, Expression, FIX-CODEPAGE statement, NEW statement