C++ syntax error: The same constructor signature appears multiple times, how to solve it?

C is a powerful programming language, but during use, you will inevitably encounter various problems. Among them, the same constructor signature appearing multiple times is a common syntax error. This article explains the causes and solutions to this error.

1. Cause of error

In C, the constructor is used to initialize the data members of the object when creating the object. However, if the same constructor signature is defined in the same class (that is, the parameter types and order are the same), the compiler cannot determine which constructor to call, causing a compilation error.

For example, the following code has the same constructor signature:

class A{
public:
    A(int a, int b){
        this->a = a;
        this->b = b;
    }
    A(int c, int d){
        this->c = c;
        this->d = d;
    }
private:
    int a, b, c, d;
};

In the above code, two identical constructor signatures are defined in class A: A(int,int ). This will cause the compiler to be unable to determine which constructor to call, resulting in a syntax error.

2. Solution

In order to solve the same constructor signature problem, we can use function overloading and function default value.

1. Function overloading

Function overloading allows us to define multiple functions with the same name but different parameter lists in the same class. Therefore, we can write different constructors for different parameter lists and avoid having the same constructor signature.

For example, for class A above, we can define the constructor in the following way:

class A{
public:
    A(int a, int b){
        this->a = a;
        this->b = b;
    }
    A(int c, int d, int e){
        this->c = c;
        this->d = d;
        this->e = e;
    }
private:
    int a, b, c, d, e;
};

In the above code, we define two different constructor signatures: A(int ,int) and A(int,int,int), thereby avoiding the same constructor signature problem.

2. Function default values

Function default values ​​allow us to provide default values ​​for the parameters of a function. Therefore, we can specify different default values ​​for the same constructor signature and avoid compilation errors.

For example, for the above class A, we can define the constructor in the following way:

class A{
public:
    A(int a, int b, int c=0, int d=0){
        this->a = a;
        this->b = b;
        this->c = c;
        this->d = d;
    }
private:
    int a, b, c, d;
};

In the above code, we define the constructor A(int,int,int,int) The last two parameters of A(int, int) specify default values, thus avoiding the same constructor signature problem as A(int, int).

3. Summary

In C, the same constructor signature will cause compilation errors. In order to avoid this error, we can use function overloading and function default values. This not only allows us to design the constructor of the class more flexibly, but also improves the readability and maintainability of the program.

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