docker ip script with bash auto completion

docker-ip.sh

#!/usr/bin/env bash

alias docker-ip="docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}'"
function _docker-ip() {
    # No need to worry about spaces in this output, because
    # docker only allows names in the form [a-zA-Z0-9][a-zA-Z0-9_.-]*
    local pos_comps=$(docker ps --format "{{.ID}} {{.Names}}")

    # $COMP_WORDS array with the current line
    # $COMP_WORD the current word we're comping
    # e.g.
    # "docker-ip bana$" COMP_WORDS=(docker-ip bana) COMP_WORD=1
    # "docker-ip bana $" COMP_WORDS=(docker-ip bana "") COMP_WORD=2

    # compgen -W "list of possible completions" -- "current word to complete"

    # We need to populate $COMPREPLY with an _array_ of possibilities.
    COMPREPLY=( $(compgen -W "${pos_comps}" -- ${COMP_WORDS[$COMP_CWORD]}) )

    return 0
}
complete -o nospace -F _docker-ip docker-ip