When an object is passed by reference to a function, the function receives a reference (or address) to the original object rather than a copy of it. This means that any modifications made to the object inside the function directly affect the original object outside the function. More specifically:
- The function parameter acts as an alias for the original object, so reading or writing to the parameter is actually reading or writing the original object itself
- This avoids the overhead of copying the entire object, making pass-by-reference more efficient in terms of memory and CPU time compared to pass-by-value
- Changes made to the object's state inside the function persist after the function returns, reflecting in the caller's context
- In languages like C++, passing by reference is done by declaring function parameters as references (using
&), allowing direct modification of the argument without copying
- In some languages like Java, objects are passed by value of their references (pass-by-value of object references), which means the reference itself is copied but both caller and callee refer to the same object, so changes to the object are visible outside the function
- In Python, arguments are passed by assignment of object references; mutable objects can be changed inside functions, affecting the caller, but rebinding the parameter to a new object does not affect the caller's reference
In summary, passing an object by reference means the function works with the original object, so modifications inside the function affect the original, unlike pass-by-value where a copy is made and changes do not affect the original object
