openhab-docs/configuration/blockly/rules-blockly-value-storage.md

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documentation	Rules Blockly - Value Storage

Value Storage

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Introduction

These blocks enable storing information for a rule that is kept after the rule has run, so it can be reused when the rule is run again later in stateful way. Basically a value storage can be perceived as a global variable for the rule instance.

• The values are persisted as a part of the instance of the rule
  • Modifying the rule during development creates a new instance which means the value is reset.
  • Restarting openHAB creates a new rule instance which also means the value is reset
  • In most cases both situations are negligible for many rules.
• If you need full persistence of values that can be used across rules you need to persist the value in one of the persistence engines like MapDB
• By default the value is undefined. To check if a value is undefined, use the special "is undefined"-block

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• TOC {:toc}

{: #blockly-value-storage-overview}

Overview of the Value Storage blocks

Value Storage Blocks

See also the short video part about Global Value Storage

Store Value

Function: Stores a value under the key name

Get Stored Value

Function: Retrieves a stored value by the key name

Check if Value is undefined

Function: Checks if a value is undefined

Example 1: Initialize a key if not set

Example 2: Use the rule instance variable to remember a color that has been set

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