Copying records

Records can be assigned to each other with the = operator.

It is possible to copy all members of a record to the members of another record, as long as the types match exactly, by using the assignment operator:

LET rec2 = rec1

Important: Record members of type DYNAMIC ARRAY, DICTIONARY and the LOB data of TEXT/BYTE members are not cloned when assigning records. A full copy of such members must be done by hand, otherwise both records will reference the same dynamic array, dictionary or LOB data.

When assigning records, both variables must have been defined with the same RECORD specification, or with the same user-type. If the types do not match exactly, the compiler will produce the error -4325:

DEFINE rec1 RECORD
            id INTEGER,
            name VARCHAR(50)
       END RECORD

DEFINE rec2 RECORD
            id INTEGER,
            name VARCHAR(100)  -- Note the difference with rec1
       END RECORD

MAIN
    LET rec2 = rec1
| The source and destination records in this record assignment statement
| are not compatible in types and/or length.
| See error number -4325.
END MAIN

Note: The .* (dot star) notation LET rec2.* = rec1.* is supported for backward compatibility and is equivalent to LET rec2 = rec1. When copying records, avoid the .* after the record names: The result at runtime is the same, but your code will benefit from more compiler verifications.

If the record structure contains sub-records on several levels, the sub-members are copied recursively:

TYPE t_person RECORD
            ...
            address RECORD
                ...
            END RECORD
       END RECORD
...
    DEFINE r1, r2 t_person
...
    LET r1 = r2   -- address sub-record is copied as well
...

If the record structure contains dynamic array or dictionary members, the runtime system will copy the reference of such members. Similarly, if the record uses BYTE/TEXT members, the (locator) handler of the large object will be copied, but the actual LOB data is not cloned. As result, after the copy, both records will point to the same array, dictionary or TEXT/BYTE data.

The next code example implements a copyTo() method for the t_reader record type, which makes a proper clone of the book_ids dynamic array:

IMPORT util

TYPE t_reader RECORD
            id INTEGER,
            name VARCHAR(100),
            book_ids DYNAMIC ARRAY OF INTEGER
       END RECORD

MAIN
    DEFINE r1, r2 t_reader

    LET r1.id = 999
    LET r1.name = "Mike Rutberg"
    LET r1.book_ids[1] = 98458
    LET r1.book_ids[2] = 98111
    DISPLAY "1: r1 books: ", util.JSON.stringify(r1.book_ids)

    CALL r1.copyTo( r2 )
    DISPLAY "2: r2 books: ", util.JSON.stringify(r2.book_ids)

    LET r1.book_ids[3] = 18234
    DISPLAY "3: r1 books: ", util.JSON.stringify(r1.book_ids)

    DISPLAY "4: r2 books: ", util.JSON.stringify(r2.book_ids)

END MAIN

FUNCTION (r t_reader) copyTo(dst t_reader INOUT)
    DEFINE bl DYNAMIC ARRAY OF INTEGER
    LET dst = r -- makes a copy of the reference of book_ids
    CALL r.book_ids.copyTo(bl) -- clone the array
    LET dst.book_ids = bl -- copy the reference to the new array
    -- Don't do this:
    -- CALL r.book_ids.copyTo(dst.book_ids)
    -- dst.book_ids and r.book_ids reference the same array!
END FUNCTION

Output:

1: r1 books: [98458,98111]
2: r2 books: [98458,98111]
3: r1 books: [98458,98111,18234]
4: r2 books: [98458,98111]

Unlike dynamic array members, static array members are fully copied, as when assigning static arrays directly.

For more details about copying TEXT/BYTE variables, see the TEXT data type.