Are there differences between initializing at start and at declaration part

Question

What are the differences between

 private Rigidbody rb { get { return GetComponent<Rigidbody> (); } set { rb = value; } }

and

 private Rigidbody rb;
 void Start () {
     rb  = GetComponent<RigidBody>();
 }

They do pretty much the same, or not? Which you prefer and why?

Answer 1

 private Rigidbody rb { get { return GetComponent (); } set { rb = value; } }

The above statement is called a "Property"

This one in particular is written incorrectly. It's called rb

Notice what will happen when you try to assign rb a value:

rb becomes equal to a value, - but oh wait, rb is a property, so let's invoke "set" on it. Fine, rb becomes equal to a value, - but oh wait, rb is a property, so let's invoke "set" on it.... This results in a recursion.

The correct way to do this would be

 private Rigidbody myPrivateRigidbody = null;//notice, private.
 public Rigidbody rb {get{return myPrivateRigidbody;} } //notice, no set here, and it's public.
 
 void Start(){
 //we can access our private variable, others will have to use property, which only has getter
     myPrivateRigidbody = null; 
 }

Basically, set allows you to assign the incoming value to anything that was declared before (never to a member variable itself, as shown in the above example)

get does the opposite. Get fetches the value from somewhere, then provides it, similar to how a function would.

So they are pretty much like Rigidbody getSomeValue(){return myPrivateRB;}or void setSomeValue(Rigidbody value){myPrivateRB = value};

As you can see, properties are very much like functions, but can be used like normal variables, without the () brackets

Are there differences between initializing at start and at declaration part

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