Why Does \'no default constructor exists for class \'Blowfish\'\' Occur and How Can It Be Fixed?

Default Constructor Error in Object Initialization

Encapsulating encryption functionality in the Blowfish class, you encountered an error when attempting to create an instance of GameCryptography. The error message, "no default constructor exists for class 'Blowfish'", indicates that a default constructor is missing.

When a class lacks a constructor, the compiler typically generates a default constructor with no arguments. However, if a non-default constructor is defined (as in this case), the compiler refrains from generating this default constructor.

Solutions

To resolve the error, you can either define a default constructor for Blowfish or modify the object initialization.

1. Adding a Default Constructor:

Add a default constructor to the Blowfish class, such as:

Blowfish() {}

This constructor will initialize the object without specifying an algorithm.

2. Specifying the Algorithm in Object Initialization:

When creating an instance of Blowfish in GameCryptography, explicitly specify the algorithm. For example:

GameCryptography::GameCryptography(unsigned char key[])
{
    _blowfish = Blowfish(CBC);
}

3. Using C 11 Default Member Initialization:

In C 11 or later, you can use default member initialization to automatically initialize members to their default values. This allows you to define a non-default constructor and still have a "default-like" constructor:

Blowfish(BlowfishAlgorithm algorithm = CBC);

GameCryptography::GameCryptography(unsigned char key[]) : _blowfish() {}  // Default-initialize _blowfish

Note on Terminology

The modes of operation (e.g., ECB, CBC, CFB) are not encryption algorithms themselves. Referencing them as algorithms may lead to confusion.

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