Pass a reference to a sensor or create the sensor object in the class

Question

Note to SO. If I ask this question to AI I get a very similar output as the accepted reply. Without out all the questions about how I asked the question. Just sayin.

I am using this class for sensors. Each sensor has multiple capabilities (Temp and Humidity....). I need to access some of the properties of the sensor beyond the output values.

class Sensor {
public:
    int id;
    int sensorTypeVal;
    const char* name; 
    SensorReading reading; 

    // Constructor to initialize Sensor with id, type, and name
    Sensor(int id, int type, const char* name)
        : id(id), sensorTypeVal(type), name(name) {} // Initialize reading with default constructor

    // Constructor to initialize Sensor with id, type, name, and a SensorReading
    Sensor(int id, int type, const char* name, const SensorReading& reading)
        : id(id), sensorTypeVal(type), name(name), reading(reading) {}

    // Method to update the sensor reading
    void updateReading(const SensorReading& newReading) {
        reading = newReading;
    }
};

Fairly new to C++ so wondering what the normal approach is here. I found this Why should I use a pointer rather than the object itself? Which seems a level up from my question. I don't want to get into the sensor "wrapper" pattern and start duplicating properties across layers. Is it recommended to pass a ref to the sensor in on init, or move the sensor object inside the class and abstract it away?

Or is there another way to compose it?

Answer 1

Sensor is a class, there is a generally a library where the "sensor" is created such as Adafruit_AHTX0 aht; I can also create a ref like so Adafruit_AHTX0& raht = aht; Is it better to create the 'sensor' and the reference outside the class in the main program, or have private methods in the class that init the Adafruit_AHTX0 aht;

When you Adafruit_AHTX0 aht; you create an instance of the class Adafruit_AHTX0 ie you allocate the memory for the class, and the default constructor is being called. The latter creates reference (alias) to the instance of the class Adafruit_AHTX0.

The place whe you create the instance of the class depends of the program needs but if has quite importan repercusions:

1. Memory used and constructor call timing

Scope	Memory Segment	Lifetime	Constructor Call	Access
Global	Global/Static segment	Entire program duration	Before main() starts	Accessible across the program (if not static).
Local (Stack)	Stack memory	Within the enclosing block	When the block or function is entered	Limited to its function/block.
Dynamic (Heap)	Heap memory	Until explicitly deallocated	When new is called	Accessible via pointers.
Static (Local)	Global/Static segment	Persistent across the program (initialized only once)	First time the block is executed	Limited to its function/block.
Static (Global)	Global/Static segment	Entire program duration	Before main() starts	Accessible across the program.

Small embedded targets have their specific needs - nor necessary following the best practices for "normal" big computers. It is very broad topic far beyond a simple SO answer.