Installing Watchman

Watchman is a tool used internally by React Native. Its purpose is to watch files for updates, and trigger responses (such as live reloading) when changes occur. The Expo documentation recommends installing Watchman, since it has been reported that some macOS users have run into issues without it. The recommended method for installing Watchman is via Homebrew. The missing package manager for macOS, Homebrew allows you to install a wide array of useful programs straight from your Terminal. It's an indispensable tool that should be in every developer's tool bag:

1. If you don't have Homebrew installed already, run the following command in the Terminal to install it (you can read more about it and view the official documentation at https://brew.sh/):

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

1. Once Homebrew has been installed, run the following two commands in Terminal to install watchman:

brew update
brew install watchman