# method chain 方法鏈
last update 2024/11/22
[C++方法链式调用_c++链式调用-CSDN博客](https://blog.csdn.net/weixin_39126199/article/details/130621048)
recall:copy assigment operator
method chain(chaining call) 跟 chaining assigment的概念相同，原因是他們都是return呼叫該方法/運算子的物件的引用(\*this)或是pointer。

區別在於用法:
1. 方法鏈 : 同一個物件鏈式呼叫不同的方法 chaining call

obj.Method1().Method2().Method3();

2. chaining assigment : (同一個class/type的)不同物件各自呼叫同一個operator

MyClass obj1, obj2, obj3;
obj1 = obj2 = obj3;

## reference
:::spoiler reference

#include <iostream>

class MyClass {
public:
    MyClass& Method1() {
        std::cout << "Method1 is called" << std::endl;
        return *this;
    }
    MyClass& Method2() {
        std::cout << "Method2 is called" << std::endl;
        return *this;
    }
    MyClass& Method3() {
        std::cout << "Method3 is called" << std::endl;
        return *this;
    }
};

int main() {
    MyClass obj;
    obj.Method1().Method2().Method3();
    return 0;
}

:::
## pointer
::: spoiler pointer

#include <iostream>

class MyClass {
public:
    MyClass* Method1() {
        std::cout << "Method1 is called" << std::endl;
        return this;
    }
    MyClass* Method2() {
        std::cout << "Method2 is called" << std::endl;
        return this;
    }
    MyClass* Method3() {
        std::cout << "Method3 is called" << std::endl;
        return this;
    }
};

int main() {
    MyClass* obj = new MyClass;
    obj->Method1()->Method2()->Method3();
    delete obj;
    return 0;
}

:::