通过 context-storage 更新 node-red 中的文件答案

【问题标题】：update a file in node-red through context-storage通过 context-storage 更新 node-red 中的文件
【发布时间】：2018-01-23 15:51:58
【问题描述】：

我已经编写了代码来更新 node-red 中的文件，该文件可以按我的意愿工作。我不太确定它是否可行。当按下注入按钮时，当前值通过上下文存储，读取文件并将存储的数据添加到其中。（a-）同步性怎么样？如果存储的数据变大了怎么办？也许数据还没有被存储，但旧数据被写入文件？这是可能的吗？我可以通过某种方式使用某种回调函数来解决这个问题吗？

这是节点红色代码：

[{"id":"ff428878.2bf0d8","type":"inject","z":"33a0c3f0.5ad66c","name":"","topic":"","payload" :"","payloadType":"date","repeat":"","crontab":"","once":false,"x":140,"y":80,"wires":[[ "d97f4731.48f508"]]},{"id":"aff66bbc.653048","type":"file in","z":"33a0c3f0.5ad66c","name":"","filename": "examplefile.txt","format":"utf8","chunk":false,"sendError":false,"x":380,"y":240,"wires":[["82b889ff.4e5f18"] ]},{"id":"216dc166.5c79be","type":"file","z":"33a0c3f0.5ad66c","name":"","filename":"examplefile.txt"," appendNewline":true,"createDir":false,"overwriteFile":"true","x":900,"y":80,"wires":[]},{"id":"9238c649.dac2e8", "type":"function","z":"33a0c3f0.5ad66c","name":"merge","func":"if(msg.topic == \"new\"){\n context.set ('shortterm', msg.payload);\n return [null,msg];\n}\n\nif(msg.topic == \"old\"){\n msg.payload.push(context.get ('shortterm'));\n return [msg,null];\n}\n\n","outputs":"2","noerr":0,"x":611,"y":80 ,"电线":[["216dc166.5c79be"],["aff66bbc.653048"]]},{"id":"d97f4731.48f508","t ype":"function","z":"33a0c3f0.5ad66c","name":"mark as new","func":"msg.topic = \"new\";\nreturn msg;","outputs ":1,"noerr":0,"x":400,"y":80,"wires":[["9238c649.dac2e8"]]},{"id":"10b8938f.1cddfc","type ":"function","z":"33a0c3f0.5ad66c","name":"标记为旧","func":"msg.topic = \"old\";\nreturn msg;","outputs" :1,"noerr":0,"x":810,"y":240,"wires":[["9238c649.dac2e8"]]},{"id":"82b889ff.4e5f18","type" :"function","z":"33a0c3f0.5ad66c","name":"JSON 解析","func":"if(msg.payload){\n msg.payload = JSON.parse(msg.payload) ;\n}\n\nreturn msg;","outputs":1,"noerr":0,"x":610,"y":240,"wires":[["10b8938f.1cddfc"]]} ,{"id":"7572637c.0a25ac","type":"file","z":"33a0c3f0.5ad66c","name":"","filename":"examplefile.txt","appendNewline" :true,"createDir":false,"overwriteFile":"true","x":510,"y":480,"wires":[]},{"id":"1f6b9043.ff153","type ":"inject","z":"33a0c3f0.5ad66c","name":"","topic":"","payload":"[]","payloadType":"json","repeat" :"","crontab":"25 22 * * *","once":false,"x":210,"y":460,"wires":[["7572637c .0a25ac"]]}]

【问题讨论】：

标签： node-red

【解决方案1】：

如果您使用单个流程来读取文件，则流程中的下一步将在文件被读取之前不会发生。

所以你的流程太复杂了。

inject->read file->json node (if the file content is json)->
  function node->write file

函数节点所在位置：

获取上下文变量（如果不存在则创建一个空变量）
将文件数据与上下文合并
写入上下文变量
将msg.payload 更改为更新后的内容
return msg

【讨论】：

【解决方案2】：

Node-Red 19.0+ 持久文件存储的另一个较新选项是内置的“上下文存储”。

这里有一篇关于如何使用上下文存储滚动的很好的文章：

https://discourse.nodered.org/t/a-guide-to-understanding-persistent-context/4115

基础是使用 contextStorage 设置更新您的 ~/.node-red/settings.js 文件：

contextStorage: { default : { module: "memory" }, fileStore: { module: "localfilesystem"} },

从那里您可以在流程中引用：

flow.set("jsObj", "Hello there!", "fileStore");

要取回数据：

flow.get("jsObj", "fileStore")

此时您可以在 ~/.node-red/context/ 文件夹中看到您保存的文件。

上面的链接文章应该可以回答任何其他问题。

【讨论】：