TypeDef

Can anyone elaborate on using typedefs as opposed to copy replacing.  I don't understand the concept and the little bit of reading that I found does not help much.  Is this a better way of coding working-storage items?  Please provide example code if possible.

#VisualCOBOL

typedefs actually come from other programming languages such as C and C . They are used to give a more meaningful name to existing types or to create user-defined data types that can be referenced in a usage clause.

A pretty good explanation can be found here:
stackoverflow.com/.../what-is-the-use-of-typedef

A good example of where we use these can be found in the copybook in the Visual COBOL\\cpylib folder called cbltypes.cpy.

01 my-buffer typedef.
05 my-name pic x(20).
05 my-city pic x(20).

01 my-buffer1 my-buffer.
01 my-buffer2 my-buffer.

move "Chris" to my-name of my-buffer1
move "Boston" to my-city of my-buffer1
move "Mary" to my-name of my-buffer2
move "Detroit" to my-city of my-buffer1


Doing a similar thing with a copybook would be:

file mybuffer.cpy
05 my-name pic x(20).
05 my-city pic x(20).

then reference:

01 my-buffer1.
copy mybuffer.cpy.
01 my-buffer2.
copy mybuffer.cpy.

move "Chris" to my-name of my-buffer1
move "Boston" to my-city of my-buffer1
move "Mary" to my-name of my-buffer2
move "Detroit" to my-city of my-buffer1

You could define many different typedefs in one file and then bring them in with a single copy statement. When using copy or copy replacing you would have to have a different copybook for each unique record structure you wished to define.


Does this help any?

Can anyone elaborate on using typedefs as opposed to copy replacing.  I don't understand the concept and the little bit of reading that I found does not help much.  Is this a better way of coding working-storage items?  Please provide example code if possible.

#VisualCOBOL

Adding on from what Chris has said, with careful use of typedef it could aid you in further expansion of your application at a later stage.

For example you decide to define a StockItem as a Pic x(10) and you have working storage fields, copy books to support this. 5 years down the line you get a request to change the StockItem to a Pic x(15), that could amount to some serious time consuming work.

So you could do this :

77 stockItemTD is typedef pic x(10).

01 stockItem stockItemTD.
01 ws-stock-item stockItemTD.


5 years later I could just change the 77 level to 15 and recompile.

77 stockItemTD is typedef pic x(15).

Neil

Can anyone elaborate on using typedefs as opposed to copy replacing.  I don't understand the concept and the little bit of reading that I found does not help much.  Is this a better way of coding working-storage items?  Please provide example code if possible.

#VisualCOBOL

Adding on from what Chris has said, with careful use of typedef it could aid you in further expansion of your application at a later stage.

For example you decide to define a StockItem as a Pic x(10) and you have working storage fields, copy books to support this. 5 years down the line you get a request to change the StockItem to a Pic x(15), that could amount to some serious time consuming work.

So you could do this :

77 stockItemTD is typedef pic x(10).

01 stockItem stockItemTD.
01 ws-stock-item stockItemTD.


5 years later I could just change the 77 level to 15 and recompile.

77 stockItemTD is typedef pic x(15).

Neil