I recently spent more time than was necessary trying to figure out the “snappy” way of enabling wifi on my Raspberry Pi 2. After reading through the documentation, I was expecting to find an elegant snap or framework. Instead, in recent images all that’s required is to add to the following to /etc/interfaces.d/wlan0.

allow-hotplug wlan0
iface wlan0 inet dhcp
  wpa_ssid <SSID>
  wpa_psk <passphrase>