Re: Passing Files as Parameters

On 2010/11/4 6:47 AM, David FOXWELL wrote:

... I'm not fully appreciating the advantages of this feature.
Would that be that it permits having all file operations in the
callee? With the file having to be declared in both caller and
callee, I don't really get the advantage.

Also, WHAT exactly is being passed as the first parameter? Why is the
file template not in the caller instead of the callee? What's the
advantage over declaring the files in both caller and callee and
passing only 2 parameters, the key and the record? Thanks!

David, if you do want to separate your file operations into another module or service program, then it can be easier to define the actual file in the caller and pass it as a parameter to the procedures in the service program. The alternative is to define the actual file in the service program, but then there is the possibility of inadvertent file "sharing" if more than one program calls that service program.

If more than one module is involved, then normally the template file would be in a /copy file that is copied into both modules. The module declaring the actual file would use LIKEFILE to define it.

What is being passed is RPG's internal data structure that it uses to keep track of the file.

If you define the files in both caller and callee, and want them to work together with the same "file-open", then you have to share the file. Not necessarily a problem, but the scope of the share is for the entire activation group (or job). With file parameters, you explicitly "share" the file-open and can control exactly which modules or procedures can see the file-open.