107 lines
2.3 KiB
C++
107 lines
2.3 KiB
C++
//
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// Created by light on 19-11-3.
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//
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#include <iostream>
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#include <complex>
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using namespace std;
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class Zoo {
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public:
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Zoo(int a, int b) : a(a), b(b) {
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cout << "with param ctor \n";
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}
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Zoo() = default;
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Zoo(const Zoo &) = delete; // copy ctor
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Zoo(Zoo &&) = default; // move ctor
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Zoo &operator=(const Zoo &) = default; // copy assignment
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Zoo &operator=(const Zoo &&) = delete; // move assignment
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// 一般函数可以使用=default或=delete?
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// void fun1()= default; // error: ‘void Zoo::fun1()’ cannot be defaulted
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void fun1() = delete; // compile ok
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// 析构函数可以使用=default或=delete?
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// ~Zoo()= delete; // ok,但是造成使用Zoo object出错
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~Zoo() = default;
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// 上述得出=delete可以使用在任何函数身上,而=default不可以使用在普通函数上
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// 上述会联想到=0,=0只能用在virtual funciton上
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private:
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int a, b;
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};
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class Empty {
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};
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// 等价于 编译器给出的默认版本函数都是public且inline
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class Empty1 {
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public:
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Empty1() {}
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Empty1(const Empty1 &rhs) {}
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~Empty1() {}
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};
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// no-copy
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// copy ctor与copy assignment都delete掉
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struct NoCopy {
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NoCopy() = default;
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NoCopy(const NoCopy &) = delete;
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NoCopy &operator=(const NoCopy &) = delete;
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~NoCopy() = default;
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};
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// no-dtor
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struct NoDtor {
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NoDtor() = default;
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~NoDtor() = delete;
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};
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// 对no-copy的改进 将copy ctor与copy assignment 放到private ,但是可以对member与friend调用
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// boost::noncopyable 就用到了PrivateCopy
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class PrivateCopy {
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private:
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PrivateCopy(const PrivateCopy &) {};
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PrivateCopy &operator=(const PrivateCopy &) {};
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public:
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PrivateCopy() = default;
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~PrivateCopy() {};
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};
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// 继承了的都拥有PrivateCopy性质
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class Foo : public PrivateCopy {
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};
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int main() {
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Zoo z;
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Zoo z1(1, 2);
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// Zoo z2=z; // error copy ctor delete
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z = z1;
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complex<int> a; // 内部不带指针的可以不用写 big three 没有析构 有copy ctor与copy assignmetn 都是使用=default,没有自己写
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string s; // 内部带指针的有big five
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// NoDtor n; //error no-dtor 不能够自动delete
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// NoDtor *p=new NoDtor; // ok
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// delete p; // error no-dtor 不能够delete
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Foo foo;
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Foo foo1;
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// foo = foo1; // 继承了的都拥有PrivateCopy性质
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return 0;
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} |