Contents
How to use context in a custom node?
The Writing Functions guide describes how to use context in the Function node. The Creating Nodes guide describes how to use context in a custom node. Context can be permanently deleted by using a Change node set to delete.
How do you set a value in context?
Using context in a flow. The easiest way to set a value in context is to use the Change node. For example, the following Change node rule will store the value of msg.payload in flow context under the key of myData. Various nodes can access context directly.
How to store context data in Node-RED?
The contextStorage property in settings.js can be used to configure how context data is stored. Node-RED provides two built-in modules for this: memory and localfilesystem. It is also possible to create custom store plugins to save the data elsewhere.
When to use context or scope in flow?
Flow – visible to all nodes on the same flow (or tab in the editor) The choice of scope for any particular value will depend on how it is being used. If a value only needs to be accessed by a single node, such as a Function node, then Node context is sufficient. More often context allows some sort of state to be shared between multiple nodes.
How to access context in Node-RED 0.20?
From Node-RED 0.20, the nodes inside a subflow can access the context of the parent flow by prepending $parent. to the context key. For example: By default, context is stored in memory only. This means its contents are cleared whenever Node-RED restarts.
Where is the context stored in Node-RED?
Context stores. By default, context is stored in memory only. This means its contents are cleared whenever Node-RED restarts. With the 0.19 release, it is possible to configure Node-RED to save context data so it is available across restarts. The contextStorage property in settings.js can be used to configure how context data is stored.
Can a node access the context of a parent flow?
Note : for nodes in a subflow, the flow context is shared by those nodes and not the flow the subflow is on. From Node-RED 0.20, the nodes inside a subflow can access the context of the parent flow by prepending $parent. to the context key.
Can a switch node access the context store?
Various nodes can access context directly. For example, the Inject node can be configured to inject a context value and the Switch node can route messages based on a value stored in context. If you have multiple context stores configured, the UI will allow you to pick which store a value should be stored in.