在不同的类继承级别调用函数链

发布于 2024-11-03 02:48:07 字数 778 浏览 1 评论 0原文

鉴于：

class Foo {
 public:
   void Method1();
}
class Bar extends Foo {
 public:
   Bar* Method2();
}
class Baz extends Bar {
 public:
   Baz* Method3();
}

所以，

someObject *b = new Baz();
b->Method3()->Method2()->Method1();

这将起作用，因为 Baz() 包含所有方法，包括 Method2()，Bar 包含 Method1()< /代码>;

但是，由于返回类型的原因，这似乎是一个坏主意 - 在调用更复杂的 Method3() 之前在第一个继承级别访问更简单的 Method1() 时，和必须将此调用保持在单行中。

b->Method1()->Method2()->Method(3); // will not work?

另外，有人告诉我，将 try.. catch.. throw 放入其中一个 Method's 中有时会退出链而不以错误的值调用下一个方法。这是真的吗？

那么如何在C++中正确实现方法链呢？

原文

Given:

class Foo {
 public:
   void Method1();
}
class Bar extends Foo {
 public:
   Bar* Method2();
}
class Baz extends Bar {
 public:
   Baz* Method3();
}

So,

someObject *b = new Baz();
b->Method3()->Method2()->Method1();

This will work, as Baz() contains all methods including Method2(), Bar contains Method1();

But, due to return type this seems to be a bad idea - when accessing simpler Method1() at first inheritance level before calling more complex Method3(), and having to keep this calls in single line..

b->Method1()->Method2()->Method(3); // will not work?

Also, someone told me that putting try.. catch.. throw inside one of those Method's will occasionally exit the chain without calling next method at wrong value. Is this true?

So how to properly implement method chaining in C++?

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似最初 2024-11-10 02:48:07

这就是虚拟方法的用途。从语法错误中我推测您是 C++ 新手

struct Base
{
    virtual Base* One() { return this; };
    void TemplateMethod() { this->One(); }
};

struct Derived : public Base
{
    virtual Base* One() { /* do something */ return Base::One(); }
};

当您调用 TemplateMethod 时：

int main() 
{ 

      Base* d = new Derived();
      d->TemplateMethod(); // *will* call Derived::One() because it's virtual

      delete d;

      return 0;
}

That's what virtual methods are for. From the syntax errors I gather that you are new to C++

struct Base
{
    virtual Base* One() { return this; };
    void TemplateMethod() { this->One(); }
};

struct Derived : public Base
{
    virtual Base* One() { /* do something */ return Base::One(); }
};

When you call TemplateMethod:

int main() 
{ 

      Base* d = new Derived();
      d->TemplateMethod(); // *will* call Derived::One() because it's virtual

      delete d;

      return 0;
}

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