When Should You Use Initialization Lists in C ?

Advantages of Initialization Lists

Initialization lists enhance the efficiency of initializing class members, particularly those of custom classes. Consider the following code snippet:

Fred::Fred() : x_(whatever) { }

Compared to the alternative approach:

Fred::Fred() { x_ = whatever; }

Using an initialization list is advantageous when x is an instance of a custom class. This approach offers improved performance because the compiler directly constructs the result of the whatever expression within x_, avoiding the creation of a separate temporary object.

However, this benefit may not apply to all scenarios. For example, in the following code:

class MyClass
{
public:
    MyClass(string n) : name(n) { }
private:
    string name;
};

Compared to the alternative version:

class MyClass
{
public:
    MyClass(string n)
    {
        name = n;
    }
private:
    string name;
};

In this instance, using an initialization list does not provide any efficiency gain. The second version calls the default constructor of string and then the copy-assignment operator, potentially involving unnecessary memory allocation and deallocation operations.

Therefore, while initialization lists generally enhance performance, it is crucial to consider the specific context and data types involved when choosing the appropriate initialization method.

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