Initializer List vs. Constructor Body: Which C Constructor Syntax Should You Use?

Initialization Syntax in Constructors: Initializer List vs. Constructor Body

In C , you have two options for initializing class member variables in a constructor:

• Initializer List:

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

• Constructor Body:

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

Comparison

While both syntaxes seem similar, they can have significant differences for non-POD (Plain Old Data) member types.

In the initializer list syntax, member variables are initialized before the constructor body executes. This means that non-POD members with non-default constructors are guaranteed to be properly initialized.

In the constructor body syntax, member variables are initialized after the constructor body. This can lead to double initialization and compilation errors if non-POD members don't have default constructors.

Default Parameter Handling

Default parameters are not handled differently between the two syntaxes. You can use default parameters in both the initializer list and the constructor body.

Conclusion

For non-POD member types, it is recommended to use the initializer list syntax because it ensures proper initialization and prevents potential errors.

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