Node-RED使用指南：16:根据输出结果进行分支逻辑操作
在流的控制中，依据分支执行的结果可以分支结果的输出，这篇文章继续介绍Node-RED中的使用特性。
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
方式1: flow.state + switch节点
flow生成和设定
生成下图所示的flow
- Inject节点：flow.state传递结果
在Node-RED中flow.state为此节点的执行结果，可根据此节点的执行结果进行后续的逻辑判断。
- switch节点：根据flow.state传递结果进行多路分支处理
此处用了三个分支，分别对应flow.state返回0、1和2的情况
- Debug节点：显示msg.payload信息
部署并执行
点击Deploy进行部署，并通过点击Inject节点执行按钮手动触发，会发现执行结果总是显示flow.state == 0的分支，因为此处Inject的节点只是传个时间戳，并不会出错的原因。
方式2: flow.state + change节点
flow生成和设定
生成下图所示的flow
-
Inject节点：用作示例的传递输入
分别使用三个Inject节点传入flow.state为0、1和2，比如flow.state=0的值的设定如下所示：
-
change节点：将三个节点的state属性转化为payload
-
Debug节点：显示msg.payload信息
部署并执行
点击Deploy进行部署，并通过点击三个Inject节点执行按钮手动触发，结果显示如下
JSON格式的flow
[{"id":"8073b1db.7152","type":"inject","z":"73554227.4474dc","name":"多路输入：0","topic":"","payload":"0","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":190,"y":340,"wires":[["bca30b83.bb3328"]]},{"id":"223570a4.2ca28","type":"inject","z":"73554227.4474dc","name":"多路输入：0","topic":"","payload":"0","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":190,"y":380,"wires":[[]]},{"id":"fd948673.ecaf18","type":"inject","z":"73554227.4474dc","name":"多路输入：1","topic":"","payload":"1","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":190,"y":380,"wires":[["bca30b83.bb3328"]]},{"id":"532a5292.81ae0c","type":"inject","z":"73554227.4474dc","name":"多路输入：2","topic":"","payload":"2","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":190,"y":420,"wires":[["bca30b83.bb3328"]]},{"id":"bca30b83.bb3328","type":"change","z":"73554227.4474dc","name":"输入合并器","rules":[{"t":"set","p":"state","pt":"msg","to":"payload","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":390,"y":380,"wires":[["ced9de0c.8573f"]]},{"id":"ced9de0c.8573f","type":"debug","z":"73554227.4474dc","name":"结果输出显示","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":590,"y":380,"wires":[]}]