Constructors with Default Arguments in C++

 

Constructors with Default Arguments in C++

Constructors with default arguments allow you to provide pre-defined values for some parameters within your constructor's declaration. This makes your class more adaptable and easier to use in various scenarios. Let's break it down:

How it works:

1. Define a constructor with parameters where some parameters have assigned default values.
2. When creating an object, you can either:
   • Provide values for all parameters, ignoring the defaults.
   • Omit values for some parameters, and the corresponding defaults will be used.

Example:

C++

class Person {
public:
  // Default constructor with two parameters, both having defaults
  Person(std::string name = "John Doe", int age = 20) : name(name), age(age) {}

  // Other methods to access and manipulate data members
  void printInfo() {
    std::cout << "Name: " << name << ", Age: " << age << std::endl;
  }

private:
  std::string name;
  int age;
};

int main() {
  // Create object with all default values
  Person person1;

  // Create object with specific name
  Person person2("Jane Doe");

  // Create object with specific age
  Person person3("Alice", 30);

  person1.printInfo(); // Output: Name: John Doe, Age: 20
  person2.printInfo(); // Output: Name: Jane Doe, Age: 20
  person3.printInfo(); // Output: Name: Alice, Age: 30
}

Use code with caution.

Benefits:

• Flexibility: Cater to different use cases by providing defaults for optional parameters.
• Code simplification: Avoid repetitive constructors for slightly different object initializations.
• Readability: Improve code clarity by specifying common default values.

Important points:

• Default arguments must be placed at the end of the parameter list.
• Only rightmost parameters can have default values.
• If you don't provide a constructor with default arguments, the compiler will create a default constructor without any parameters.

Further applications:

• Use default arguments to set optional object flags or initial states.
• Combine default arguments with member initialization lists for concise object creation.