Methods

The receiver consists of an identifier followed by a user-defined type. The receiver identifier is then referenced in the function body as the target of this method:

TYPE Rectangle RECORD
    height, width FLOAT
END RECORD

FUNCTION (r Rectangle) area() RETURNS FLOAT
    RETURN r.height * r.width
END FUNCTION

Method names and receiver type field names must be different: It is not legal to define a method with the same name as a field of the receiver type:

PUBLIC TYPE Rectangle RECORD
    height, width FLOAT
END RECORD
...
PUBLIC FUNCTION (r Rectangle) width () RETURNS INTEGER
| Method and field names must be different. Type rectangle.Rectangle has field width.
| See error number -8427.
    RETURN r.width
END FUNCTION

The compiler is more strict regarding methods definitions, compared to regular functions. For example, when a method returns values, it must be defined with the RETURNS clause:

PUBLIC TYPE Rectangle RECORD
    height, width FLOAT
END RECORD
...
PUBLIC FUNCTION (r Rectangle) getWidth ()
    RETURN r.width
| A method without return type (RETURNS) can not return values.
| See error number -8431.
END FUNCTION

A method for type needs a variable defined to reference an instance of that type. To invoke a method, prefix the method name with the variable of the type used as receiver for the method:

DEFINE r1, r2 Rectangle
DISPLAY r1.area()
DISPLAY r2.area()

The same function name can be reused for a different receiver type. Using a different receiver type for the same function name implies another method:

FUNCTION (r Rectangle) area() RETURNS FLOAT
    RETURN r.height * r.width
END FUNCTION

FUNCTION (r Triangle) area() RETURNS FLOAT
    RETURN ( r.height * r.base ) / 2
END FUNCTION

A method for a type can implicitly modify the receiver (the receiver variable is passed by reference to the method):

FUNCTION (r Rectangle) setDimensions(w FLOAT, h FLOAT)
    CALL myAssert( (w>0 AND h>0), "Invalid dimensions!" ) -- stops program
    LET r.width = w
    LET r.height = h
END FUNCTION

When defining a method taking a structured record type as parameter, you must call the method with a record variable name. The record will be passed as a copy: The original record cannot be modified, unless the INOUT clause is used.

TYPE t_rec1 RECORD
         f1 INT
     END RECORD

TYPE t_rec2 RECORD
         f1 INT
     END RECORD

FUNCTION (r t_rec1) method1(p t_rec2)
    LET p.f1 = 999
END FUNCTION

FUNCTION (r t_rec1) method2(p t_rec2 INOUT)
    LET p.f1 = 999
END FUNCTION

FUNCTION main()
    DEFINE r1 t_rec1, r2 t_rec2
    CALL r1.method1( r2 )
    DISPLAY r2.f1 -- not modified
    CALL r1.method2( r2 )
    DISPLAY r2.f1 -- 999
    -- CALL r1.method1( r2.* ) -- invalid!
END FUNCTION

Methods can return a complete RECORD: The method must be defined with RETURNS type-name and use the RETURN clause by specifying the record variable without the .* notation (this would expand all members of the record on the stack):

TYPE t_cust RECORD
    id INT,
    name VARCHAR(50)
END RECORD

TYPE t_status RECORD
    errcode INT,
    message STRING
END RECORD

FUNCTION (r t_cust) checkData() RETURNS t_status
    DEFINE s t_status
    CASE
        WHEN r.id IS NULL OR r.id < 1
            LET s.errcode = -9
            LET s.message = "Invalid identifier"
        WHEN LENGTH(r.name) = 0
            LET s.errcode = -8
            LET s.message = "Name is empty"
    END CASE
    RETURN s
END FUNCTION

FUNCTION main()
    DEFINE r t_cust
    DEFINE s t_status

    LET s = r.checkData()
    DISPLAY s.*

    LET r.id = 101
    LET s = r.checkData()
    DISPLAY s.*

    LET r.name = "John Lambert"
    LET s = r.checkData()
    DISPLAY s.*

END FUNCTION