When Should You Use References and When Should You Use Pointers in C ?

Passing by Reference vs. Pointer in C

Determining when to pass by reference and when to pass by pointer can be a confusing matter in C . Let's explore the advantages and disadvantages of each approach.

Passing by Reference

• Advantages:

  • Modifies the actual data at the caller's location.
  • Efficient, as a direct link is established without copying.

• Disadvantages:

  • Cannot pass in literals or null values.
  • Requires the underlying data to have a valid reference.

Passing by Pointer

• Advantages:

  • Allows passing in literals and null values.
  • Provides more control over memory management.

• Disadvantages:

  • Can be less efficient due to copying the data.
  • Requires careful handling to avoid dangling pointers.

Best Practices

A general rule of thumb is to "Use references when you can and pointers when you have to." For example:

• When passing non-primitive data types (e.g., strings, vectors, maps), references are typically preferred as they allow for modification of the actual data.
• When passing in literals or null values, pointers must be used.
• In cases where memory management is critical or the caller needs to maintain explicit control over the data, pointers can be a better choice.

Example

Consider the following code snippet:

int main() {
    map<string, shared_ptr<vector<string>>> adjacencyMap;
    vector<string>* myFriends = new vector<string>();
    myFriends->push_back(string("a"));
    myFriends->push_back(string("v"));
    myFriends->push_back(string("g"));
    adjacencyMap["s"] = shared_ptr<vector<string>>(myFriends);
    return 0;
}

In this example, using a pointer to pass myFriends is appropriate because it allows us to create a new vector and then pass in a shared pointer to it. However, it's important to remember to delete myFriends explicitly to avoid memory leaks.

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