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Updated Design: Persistable Context (markdown)

Nick O'Leary 2018-03-20 16:45:41 +00:00
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Design:-Persistable-Context.md

@ -136,13 +136,16 @@ It executes plugin specific function passed in the argument `command`.
**Returns** a value that plugin specific function returns. If the plugin return nothing like a `set`, `run` will return `undefined`. **Returns** a value that plugin specific function returns. If the plugin return nothing like a `set`, `run` will return `undefined`.
## Considerations ## Considerations
* Serializing/Deserializsing JavaScript Objects
#### Serializing/Deserializsing JavaScript Objects
`Object` can be stored in current memory context, but most external storage cannot handle `Object` as it is. So Node-RED or plugin should serialize/deserialize `Object`. `Object` can be stored in current memory context, but most external storage cannot handle `Object` as it is. So Node-RED or plugin should serialize/deserialize `Object`.
> HU: Persistable Context serializes/deserializes `Objects` using JSON. > HU: Persistable Context serializes/deserializes `Objects` using JSON.
> If there are some problems, we will consider how solve those. > If there are some problems, we will consider how solve those.
>> DCJ - Agreed for version 1 >> DCJ - Agreed for version 1
* Directly accessing Object property #### Directly accessing Object property
A user can directly access Object property in current memory context as following. A user can directly access Object property in current memory context as following.
```JavaScript ```JavaScript
var onj = {"bar":1}; var onj = {"bar":1};
@ -153,7 +156,7 @@ flow.get("foo.bar"); // return 1
> If there are some problems, we will consider how solve those. > If there are some problems, we will consider how solve those.
>> DCJ - Agreed for version 1. >> DCJ - Agreed for version 1.
* key name of default storage #### Key name of default storage
In the case that `file` is not declared but `default` is declared on contextStorage, if a context data is specified like `$file.count`, Node-RED stores the key name in the default storage. In the case that `file` is not declared but `default` is declared on contextStorage, if a context data is specified like `$file.count`, Node-RED stores the key name in the default storage.
In this case, there are two options for storing the key name. In this case, there are two options for storing the key name.
@ -172,3 +175,5 @@ Cons: If a user uses a same key name for the different storages, name conflictio
My proposal is as follows. Do you agree with this option? My proposal is as follows. Do you agree with this option?
- Choose the option 2. - Choose the option 2.
- Encourage a unique key name by writing it on design note. - Encourage a unique key name by writing it on design note.
> NOL: agreed - fall back to the `default` store, and remove the store name from the key. I think having multiple storage plugins will be rare, so this is an very much an edge case.