Node-RED使用指南：13:使用Change节点处理消息

た入场券 2023-07-12 11:59 16阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70]  
在前面的文章中我们介绍过使用Change类型的节点（Node）进行内容的设定的示例，这篇文章中将结合示例继续介绍一下其他的使用方法。

# 事前准备 #

以容器方式启动Node-RED服务，启动命令如下所示：

> 启动命令：docker run -it -p 1880:1880 -v $PWD/data:/data -e TZ=Asia/Shanghai --name nodered -d nodered/node-red:1.0.4

# 使用示例1: 设定固定值 #

![在这里插入图片描述][20200308173254316.png]

*  节点设定  
    三个节点组成的flow，前后的节点只是设定了一下Name，而只有Change节点设定了返回的固定结果，详细信息如下  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 1]
 *  flow的json表示（export输出结果）

[{ "id":"82808a0c.d63888","type":"inject","z":"73554227.4474dc","name":"Change使用示例1","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":140,"wires":[["fbd30c79.e788"]]},{ "id":"fbd30c79.e788","type":"change","z":"73554227.4474dc","name":"设定固定值","rules":[{ "t":"set","p":"payload","pt":"msg","to":"","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":370,"y":140,"wires":[["46d893f2.0c394c"]]},{ "id":"46d893f2.0c394c","type":"debug","z":"73554227.4474dc","name":"显示输出","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":560,"y":140,"wires":[]}]

*  手动触发结果确认  
    执行Deploy操作之后，手动触发此flow，结果显示如下图所示：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 2]

# 使用示例2: 删除属性 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 3]

*  节点设定  
    三个节点组成的flow，前后的节点只是设定了一下Name，而只有Change节点删除了payload属性，详细信息如下  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 4]
 *  flow的json表示（export输出结果）

[{ "id":"4eb22195.140f1","type":"inject","z":"73554227.4474dc","name":"Change使用示例2","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":240,"wires":[["40c98dfa.d04bc4"]]},{ "id":"40c98dfa.d04bc4","type":"change","z":"73554227.4474dc","name":"删除payload","rules":[{ "t":"delete","p":"payload","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":370,"y":240,"wires":[["1a3e2029.70d8b"]]},{ "id":"1a3e2029.70d8b","type":"debug","z":"73554227.4474dc","name":"显示payload","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":570,"y":240,"wires":[]}]

*  手动触发结果确认  
    执行Deploy操作之后，手动触发此flow，由于删除之后缺省的Debug节点显示的为msg.payload，所以结果显示如下图所示：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 5]

# 使用示例3: 重命名属性 #

![在这里插入图片描述][20200308180044155.png]

*  节点设定  
    三个节点组成的flow，Inject的节点中设定topic属性，并设定内容如下：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 6]  
    在Change节点中将topic属性重命名（移动）为payload，这样在后续的Debug节点中就能直接输出结果了。  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpdW1pYW9jbg_size_16_color_FFFFFF_t_70 7]
 *  flow的json表示（export输出结果）

[{ "id":"8bfd7210.69d86","type":"inject","z":"73554227.4474dc","name":"Change使用示例3","topic":"Hello, this is message of Topic property","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":150,"y":340,"wires":[["7b82fb90.3413c4"]]},{ "id":"7b82fb90.3413c4","type":"change","z":"73554227.4474dc","name":"移动property","rules":[{ "t":"move","p":"topic","pt":"msg","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":370,"y":340,"wires":[["7734e70f.1ef868"]]},{ "id":"7734e70f.1ef868","type":"debug","z":"73554227.4474dc","name":"显示payload","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":570,"y":340,"wires":[]}]

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