[C++][Docs] C++ documentation for constructors is missing

[maciekgajewski]

Describe the bug, including details regarding any error messages, version, and platform.

The C++ doco contains generated documentation for methods, but not for constructors. This makes it incomplete.

Component(s)

Documentation

[amoeba]

Hi @maciekgajewski, thanks for the report.

Do you have an example of a constructor that isn't documented that you think should be? I haven't done a comprehensive search but some classes in Arrow C++ have their constructors hidden behind public interfaces (e.g., RecordBatchReader) while other classes do expose their constructor (e.g., LocalFileSystem).

[maciekgajewski]

None of the public constructors seem to be documented, and not everything can be achieved with the factory functions.

Examples:

• Array - how to create an Array from data buffer?
• TimestampType- how to create TimestampType instance with specific time unit?

[amoeba]

Right. I think a PR would be welcome then.