My version is definitely wordier, but I like it.

add-alias() {
  if [[ -z "$1"  ||  -z "$2" ]]; then
    echo "Useage: add-alias <alias_name> \"<command_to_alias>\""
    return 1
  fi
  echo "alias $1='$2'" >> ~/.bash_aliases
  source ~/.bash_aliases
  echo "Alias '$1' for command '$2' added and sourced."
  
}

And, of course, the first thing I test it with is $ add-alias alias-add add-alias.