widening cast

[SagarSontakke]

Dear All,

I am facing one problem in widening cast.

can somebody explain widening cast with example.

i have written one sample code which is giving run time error .

when i am trying to pass the subclass ref to superclass,

its giving runtime error

Thanks

Sagar

report zsvs_class no standard page heading.

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• CLASS tset DEFINITION

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*

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class test definition.

public section.

methods: display_name.

endclass. "tset DEFINITION

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• CLASS test IMPLEMENTATION

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*

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class test implementation.

method display_name.

write 😕 'Test'.

endmethod. "display_name

endclass. "test IMPLEMENTATION

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• CLASS test_1 DEFINITION

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*

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class test_1 definition inheriting from test.

public section.

methods: display_name redefinition.

methods: display_test.

endclass. "tset DEFINITION

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• CLASS test_1 IMPLEMENTATION

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*

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class test_1 implementation.

method display_test.

write 😕 'Test_1'.

endmethod. "display_test

method display_name.

• super->display_name( ).

write : / 'redefined'.

endmethod. "display_name

endclass. "test IMPLEMENTATION

start-of-selection.

data : w_test type ref to test.

data : z_test type ref to test_1.

data : itab type table of ref to test.

data : r_test type ref to test.

create object w_test .

z_test ?= w_test.

[Former Member]

Widening cast or down casting is refered as such because it changes a reference from a generalized view to a more detailed view.

The first thing you can do to your code is put the casting code in a TRY... CATCH... ENDTRY block. Something like,

TRY.

z_test ?= w_test.

CATCH cx_sy_move_cast_error.

• Do the error handling

ENDTRY.

If there is still a runtime error, check at what point is it being generated and let me know what the error is. Remember that you cannot call a function or attribute of a child class (test_1) with a with z_test after the widening cast operation cause it is still carrying a reference to the parent class (test). If you do this it WILL generate a runtime error.

When i say functions of the child class, i mean functions that dont exist in the parent class and have been introduced in the child class only.