How Can I Implement Constructor Chaining in C ?

Can I Leverage Constructor Chaining in C ?

Constructor chaining, a familiar concept to C# developers, allows for the execution of one constructor from another. This provides an efficient way to initialize objects in a parent class and its derived classes.

C 11 and Beyond: Constructor Chaining

In C 11 and later versions, constructor chaining is supported through delegating constructors. The syntax deviates slightly from C#:

class Foo {
public:
  Foo(char x, int y) {}
  Foo(int y) : Foo('a', y) {}
};

This code defines two constructors: one that takes (char x, int y) and another that takes (int y). The second constructor calls the first constructor using the this pointer to initialize x to 'a'.

C 03: Constructor Simulation

Unfortunately, C 03 does not natively support constructor chaining. However, two methods can simulate its effect:

• Default Parameters: Combine multiple constructors using default parameters.

class Foo {
public:
  Foo(char x, int y = 0); // This combines (char) and (char, int) constructors.
};

• Initialization Method: Share common code through an initialization method.

class Foo {
public:
  Foo(char x);
  Foo(char x, int y);

private:
  void init(char x, int y);
};

Foo::Foo(char x) : Foo(x, int(x) + 7) {} // Calls init(x, int(x) + 7).

Foo::Foo(char x, int y) : Foo(x, y) {} // Calls init(x, y).

void Foo::init(char x, int y) {}

By referencing the C FAQ for further guidance, you can effectively simulate constructor chaining in C 03 using these methods.

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