# 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

# Overview of the Value Storage blocks


# Value Storage Blocks

See also the short video part about youtube Global Value Storage (opens new window)

# 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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