Handler

Noun

1. One who handles something (especially manually) or someone.

   "The handler of a weapon gets a symbolic sensation of deadly power."

2. A controller, trainer, someone who handles a specified thing, animal or person (especially a prizefighter).

   "The spy's handler told him to approach the subject by posing as a dog handler."

3. An advisor or manager providing guidance to a person occupying public office or a prominent position.

   "The governor received guidance on how to best disseminate key information to the public from her handler."

4. A subroutine that handles a particular situation such as an event or exception.