[ARROW-15975] [C++] Document VisitArrayInline and type traits

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 7.0.0
• Fix Version/s: 8.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/31400

Language

C++

• Assignee: Will Jones
• Reporter: Will Jones
• Created: 18/Mar/22 22:36
• Updated: 11/Jan/23 11:41
• Resolved: 29/Mar/22 12:34

Description

In ARROW-15952, we documented the ArrayVisitor and TypeVisitor classes. But as I discovered in a cookbook PR, you can't subclass these abstract visitors and use type traits. Now I know why most visitor implementations within of Arrow don't subclasses these.

We should instead suggest users simply use the VisitArrayInline and VisitTypeInline with their visitors, and ignore the ArrayVisitor and TypeVisitor classes and associated Accept() methods. In fact, can we deprecate (or even remove) those? Do they add anything valuable?

Issue Links

• relates to: ARROW-16006 [C++][Docs] Provide row conversion example for dynamic schemas
• links to: GitHub Pull Request #12717