66 lines
1.9 KiB
Markdown
66 lines
1.9 KiB
Markdown
---
|
|
layout: documentation
|
|
title: Rules Blockly - Value Storage
|
|
---
|
|
<!-- markdownlint-disable MD036 -->
|
|
|
|
# Value Storage
|
|
|
|
[return to Blockly Reference](index.html#value-storage)
|
|
|
|
## 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
|
|
|
|
{::options toc_levels="2..4"/}
|
|
|
|
- TOC
|
|
{:toc}
|
|
|
|
{: #blockly-value-storage-overview}
|
|
|
|
## Overview of the Value Storage blocks
|
|
|
|
|
|
|
|
## Value Storage Blocks
|
|
|
|
### 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
|
|
|
|
|
|
|
|
## Return to Blockly Reference
|
|
|
|
[return to Blockly Reference](index.html#value-storage)
|