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Add QuantityType conversion to rules documentation (#675) 

Signed-off-by: Henning Treu <henning.treu@telekom.de>
pull/678/head
Henning Treu 2018-05-14 20:47:40 +02:00 committed by Jerome L
parent edd1f95bc0
commit f5eded6370
1 changed files with 26 additions and 3 deletions
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29
configuration/rules-dsl.md
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@ -512,11 +512,13 @@ val PointType location = Device_Coordinates.state as PointType
##### Number Item
A Number Items carries a **DecimalType**.
A DecimalType is also a java.lang.Number so all the conversions listed above under Dimmer Item apply to Number Item as well.
A Number Items carries either a **DecimalType** or a **QuantityType** in case the Number Item has a dimension attached (e.g. `Number:Temperature`).
DecimalType and QuantityType are also java.lang.Number so all the conversions listed above under Dimmer Item apply to Number Item as well.
Here some other commonly needed conversions:
* For DecimalType states:
```java
//convert integer_number to string containing hex_code
var String hex_code = Long.toHexString(integer_number);
@ -530,9 +532,30 @@ var MyNumber = Long.parseLong(hex, 16) as Number
var DecimalType parsedResult = DecimalType.valueOf(Long.parseLong(hex_code, 16).toString);
```
* For QuantityType states:
```java
// define a QuantityType variable
var myTemperature = 20 [°C]
// convert a quantity state into a different unit:
var fahrenheit = myTemperature.toUnit("°F")
// convert scalar value to DecimalType
var myDecimal = new DecimalType(fahrenheit.doubleValue) // myDecimal == 68
// access scalar values as int, double, float
var myInt = fahrenheit.intValue
var mydouble = fahrenheit.doubleValue
var myfloat = fahrenheit.floatValue
// check if a number item state is a QuantityType
var isQuantity = myItem.state instanceof QuantityType
```
Other useful conversions can be found under Dimmer Item.
One warning comes with DecimalType.
One warning comes with DecimalType (also holds true for QuantityType).
The full explanation is [beyond the scope of this introduction](https://community.openhab.org/t/ambiguous-feature-call-whats-wrong-designer-user-or-bug/9477/4).
To avoid an error mentioning an "Ambiguous Method Call" always cast the state of a DecimalType to a Number, not DecimalType.