Detailed explanation of C++ function parameters: the role of runtime type identification in parameter passing

C Detailed explanation of function parameters: The role of runtime type identification in parameter passing

In C, function parameter passing can be passed by value , reference passing or pointer passing implementation. Each delivery method has its own advantages and disadvantages.

Run-Time Type Identification (RTTI) is a mechanism in C to obtain the type of an object at runtime. It allows us to determine the actual type of an object even if the object is stored in a base class pointer or reference.

By using RTTI, we can achieve the following functions:

• Call virtual methods without knowing the specific type
• Determine the actual type of the object
• Dynamic conversion of object types

Using RTTI in parameter passing

In function parameter passing, RTTI can be used to implement polymorphism. Polymorphism allows us to call methods of a derived class through a base class pointer or reference. In order to achieve polymorphism, we need the following steps:

1. Declare a virtual method in the base class.
2. Override virtual methods in derived classes.
3. Use RTTI to determine the actual type of an object at runtime.
4. Call the corresponding method according to the object type.

Practical Case

Consider the example in the following code:

#include <iostream>

using namespace std;

class Base {
public:
    virtual void print() {
        cout << "Base class print" << endl;
    }
};

class Derived : public Base {
public:
    void print() {
        cout << "Derived class print" << endl;
    }
};

void printObject(Base* obj) {
    // 使用 RTTI 确定对象的实际类型
    if (dynamic_cast<Derived*>(obj)) {
        // 如果对象是派生类类型，调用派生类方法
        static_cast<Derived*>(obj)->print();
    } else {
        // 否则，调用基类方法
        obj->print();
    }
}

int main() {
    Base* baseObj = new Base();
    printObject(baseObj);  // 输出：Base class print

    Derived* derivedObj = new Derived();
    printObject(derivedObj);  // 输出：Derived class print

    return 0;
}

In this case, the printObject function Use RTTI to determine the actual type of the object passed to it. If the object is of a derived class type, it calls the derived class method. Otherwise, it calls the base class method.

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