Differences Between Default and Non-Default Constructors in C
Differences Between Default and Non-Default Constructors in C
In C , constructors are special member functions that are called when an object of a class is instantiated. This article focuses on the differences between default and non-default constructors, explaining their definitions, usages, and key differences.
Default Constructor
Definition: A default constructor is a constructor that can be called with no arguments. It can either be explicitly defined by the programmer or implicitly provided by the compiler if no constructors are defined.
Usage: It initializes the object with default values. If no default constructor is provided and no other constructor is defined, the compiler will provide a default constructor that initializes member variables to their default values (e.g., zero for fundamental types and calls the default constructor for class types).
Syntax:
class MyClass { public: MyClass() { // Initialization code } // ... }Implicit Default Constructor
If no constructors are defined, the compiler provides a default constructor that initializes member variables to their default values. For example:
class MyClass { public: MyClass(); // No parameters provided // ... }In this case, the compiler will automatically create a default constructor that initializes member variables to their default values.
Non-Default Constructor
Definition: A non-default constructor requires one or more parameters. It is used to initialize an object with specific values at the time of creation.
Usage: It allows for more control over the initialization of an object, providing flexibility in setting initial values based on the programmer's requirements.
Syntax:
class MyClass { public: MyClass(int x) { // Initialization code using x } // ... }Key Differences
Parameters:
Default Constructor: No parameters required. Non-Default Constructor: One or more parameters are required.Initialization:
Default Constructor: Initializes with default values (e.g., zero for integers, empty strings, etc.). Non-Default Constructor: Initializes with values provided as arguments.Compiler Behavior:
If no constructors are defined, the compiler provides a default constructor. If a non-default constructor is defined and no default constructor is provided, the compiler does not create a default constructor. This can lead to compilation errors if an object is instantiated without arguments.Example
Here is a complete example illustrating both types of constructors:
include iostream class MyClass { public: int value; // Default constructor MyClass() : value(0) { std::cout "Default constructor called with default value " value std::endl; } // Non-default constructor MyClass(int x) : value(x) { std::cout "Non-default constructor called with value" value std::endl; } }; int main() { MyClass obj1; // Calls default constructor MyClass obj2(10); // Calls non-default constructor return 0; }Output:
Default constructor called with default value 0 Non-default constructor called with value10
Summary
In summary, the choice between using a default or non-default constructor depends on whether you need to provide initial values for your objects or if default initialization suffices. Understanding these constructors is crucial for effective object-oriented programming in C .