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Update Shuffleboard docs to recommend lambda functions for dynamic data #3129

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Update Shuffleboard docs to recommend lambda functions for dynamic data #3129

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22 changes: 13 additions & 9 deletions source/docs/software/dashboards/shuffleboard/layouts-with-code/sending-data.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -21,19 +21,21 @@ Sending simple data (numbers, strings, booleans, and arrays of these) is done by
Shuffleboard.getTab("Tab Title").add("Pi", 3.14)
```

If data needs to be updated (for example, the output of some calculation done on the robot), call ``getEntry()`` after defining the value, then update it when needed or in a ``periodic`` function
If data needs to be updated (for example, the output of some calculation done on the robot), use the type-specific methods (``addNumber``, ``addString``, ``addBoolean``) with a lambda function (Java) or callable (Python) that returns the current value. Shuffleboard will automatically call this function periodically to get the latest value.

.. tab-set-code::

```java
class VisionCalculator {
private ShuffleboardTab tab = Shuffleboard.getTab("Vision");
private GenericEntry distanceEntry =
tab.add("Distance to target", 0)
.getEntry();
private double distanceToTarget = 0;

public VisionCalculator() {
tab.addNumber("Distance to target", () -> distanceToTarget);
}

public void calculate() {
double distance = ...;
distanceEntry.setDouble(distance);
distanceToTarget = /* calculate distance */;
}
}
```
Expand All @@ -42,12 +44,14 @@ If data needs to be updated (for example, the output of some calculation done on
from wpilib.shuffleboard import Shuffleboard
def robotInit(self):
tab = Shuffleboard.getTab("Vision")
self.distanceEntry = tab.add("Distance to target", 0).getEntry()
tab.addNumber("Distance to target", lambda: self.distanceToTarget)
self.distanceToTarget = 0
def teleopPeriodic(self):
distance = self.encoder.getDistance()
self.distanceEntry.setDouble(distance)
self.distanceToTarget = self.encoder.getDistance()
```

.. important:: The NetworkTables entry API (using ``getEntry()`` and ``setDouble()``/``setString()``/etc.) should only be used for reading data *from* Shuffleboard, such as values from sliders, text fields, or number inputs. For sending data *to* Shuffleboard, prefer the lambda/callable approach shown above.

## Making choices persist between reboots

When configuring a robot from the dashboard, some settings may want to persist between robot or driverstation reboots instead of having drivers remember (or forget) to configure the settings before each match.
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