Working with Parameters in ROS2: A Quick Example

1️⃣ Defining Parameters:
Using ParameterDescriptor, we define parameters like focal_length with details such as:
- Type: PARAMETER_DOUBLE
- Description: "Focal length in mm"
- Range: 1.0 to 100.0, step 0.1

2️⃣ Access & Modify Parameters:
- Use the CLI with commands like ros2 param get/set.
- Alternatively, use a GUI to adjust values in real time for better flexibility and usability.

3️⃣ Error Handling:
ROS2 comes with built-in methods to validate parameters based on their descriptors. For example, if you try setting focal_length to 40.44 (which doesn't match the step size of 0.1), you get a precise error:

"Setting parameter failed: The value is not close enough to a valid step."

❗️This means ROS2 ensures parameters strictly follow the defined constraints—like ranges, step increments, and types—without requiring custom validation logic in your code.

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