PublishSubscribe(PubSub) 模式

当 Bash 项目变成库时，添加新功能变得很困难。通常需要在使用它们的脚本中更改函数名称，变量和参数。在这样的场景中，解耦代码并使用事件驱动的设计模式是有帮助的。在所述模式中，外部脚本可以订阅事件。当触发（发布）该事件时，脚本可以执行它在事件中注册的代码。

pubsub.sh：

    #!/usr/bin/env bash

    #
    # Save the path to this script's directory in a global env variable
    #
    DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

    #
    # Array that will contain all registered events
    #
    EVENTS=()

    function action1() {
        echo "Action #1 was performed ${2}"
    }

    function action2() {
        echo "Action #2 was performed"
    }

    #
    # @desc   :: Registers an event
    # @param  :: string $1 - The name of the event. Basically an alias for a function name
    # @param  :: string $2 - The name of the function to be called
    # @param  :: string $3 - Full path to script that includes the function being called
    #
    function subscribe() {
        EVENTS+=("${1};${2};${3}")
    }

    #
    # @desc   :: Public an event
    # @param  :: string $1 - The name of the event being published
    #
    function publish() {
        for event in ${EVENTS[@]}; do
            local IFS=";"
            read -r -a event <<< "$event"
            if [[  "${event[0]}" ==  "${1}" ]]; then
                ${event[1]} "$@"
            fi
        done
    }

    #
    # Register our events and the functions that handle them
    #
    subscribe "/do/work"           "action1" "${DIR}"
    subscribe "/do/more/work"      "action2" "${DIR}"
    subscribe "/do/even/more/work" "action1" "${DIR}"

    #
    # Execute our events
    #
    publish "/do/work"
    publish "/do/more/work"
    publish "/do/even/more/work" "again"

跑：

chmod +x pubsub.sh
./pubsub.sh