How to Choose the Right Parameter Passing Mechanism in C ?

How to Pass Parameters Correctly

Understanding Passing Mechanisms

Passing by Value: Creates a new copy of the argument; the original remains unchanged.
Passing by lvalue Reference: Modifies the original object; requires a stable identity (lvalue).
Passing by lvalue Reference to Const: Observes the original object without modifying it; accepts both lvalues and rvalues.
Passing by rvalue Reference: Binds to rvalues (temporaries or move-from objects); can perform move operations.

Best Practices

Use lvalue Reference for Modifications:
When a function needs to modify the original object, pass by lvalue reference (&).

Use lvalue Reference to Const for Observation:
For functions that only observe the state of the object, pass by lvalue reference to const (const &).

Consider Passing by Value for Non-Copy-Intensive Types:
If copies are inexpensive (e.g., integers, chars), consider passing by value.

Overload for Lvalues and Rvalues (if necessary):
Create separate overloads if expensive moves are involved and you want to avoid moves from lvalues.

Utilize Perfect Forwarding for Generic Handling:
Use function templates and std::forward to automatically determine whether to copy or move based on the argument type (rvalue/lvalue).

Example Analysis

CreditCard Class: Consider overloading the constructor with two versions:

CreditCard(CreditCard const& other); // lvalue reference to copy
CreditCard(CreditCard&& other); // rvalue reference to move

Account Class with CreditCard Member:
Use one of the following constructors based on the desired behavior:

Account(std::string number, float amount, CreditCard const& creditCard); // Copy
Account(std::string number, float amount, CreditCard&& creditCard); // Move

Account Class with Vector of Accounts Member:
Pass by reference or const reference, depending on whether modifications are expected.

Client(std::string firstName, std::string lastName, std::vector<Account> accounts); // Reference for modification
Client(std::string firstName, std::string lastName, std::vector<const Account> accounts); // Reference to const for observation

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