Initializer List or Constructor Body: Which is Better for C Field Initialization?

Initializer List vs. Constructor Body for Field Initialization

In C , there are two common approaches for initializing fields within a constructor's body: using an initializer list or assigning values directly within the body. While these approaches may seem similar, there are some key differences that developers must be aware of, particularly when dealing with non-trivial data types.

Initializer List Syntax

Using an initializer list allows fields to be initialized at the beginning of the constructor's body. The syntax is:

public : Thing(int _foo, int _bar): member1(_foo), member2(_bar) {}

In this example, member1 and member2 are assigned values within the initializer list itself.

Constructor Body Syntax

Assigning values directly within the constructor's body involves using the assignment operator after the initializer list or in its absence. The syntax is:

public : Thing(int _foo, int _bar){
    member1 = _foo;
    member2 = _bar;
}

Key Differences

Initialization Order:

The primary difference between the two approaches lies in the order of field initialization. When using the initializer list, fields are initialized before the execution of the constructor's body. This means that if a constructor throws an exception before all fields have been initialized, the object's state will remain partially constructed.

Default Parameter Handling:

The initializer list approach can handle default parameters more efficiently than assigning values directly within the body. With default parameters, the initializer list only contains those fields that are explicitly initialized. This ensures that default values are not assigned twice.

Safety Considerations:

Using the initializer list is generally considered safer for non-trivial data types. It ensures proper initialization and avoids potential issues with default parameters. If a non-POD data type lacks a default constructor, using the initializer list to explicitly initialize all fields is crucial.

Conclusion:

While both initializer lists and assigning values directly within the constructor's body can be used to initialize fields, the initializer list approach provides several advantages, particularly for non-POD data types. It ensures consistent initialization, handles default parameters efficiently, and promotes safer programming practices.

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