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关于智能指针和拷贝构造函数的一个例子

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 楼主| keer_zu 发表于 2022-10-9 16:31 | 显示全部楼层 |阅读模式
代码：
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  1. #include <iostream>
    

  2. #include <memory>
    


  3. 

  4. using namespace std;
    


  5. 

  6. class B;    //声明
    

  7. class A
    

  8. {
    

  9. public:
    

  10.     shared_ptr<B> pb_;
    

  11.     ~A()
    

  12.     {
    

  13.         cout << "A delete\n";
    

  14.     }
    

  15. };
    


  16. 

  17. class B
    

  18. {
    

  19. public:
    

  20.     shared_ptr<A> pa_;
    

  21.     ~B()
    

  22.     {
    

  23.         cout << "B delete\n";
    

  24.     }
    

  25. };
    


  26. 

  27. void test_w()
    

  28. {
    

  29.     shared_ptr<B> pb(new B());
    

  30.     shared_ptr<A> pa(new A());
    

  31.     cout << pb.use_count() << endl;    //1
    

  32.     cout << pa.use_count() << endl;    //1
    

  33.     pb->pa_ = pa;
    

  34.     pa->pb_ = pb;
    

  35.     cout << pb.use_count() << endl;    //2
    

  36.     cout << pa.use_count() << endl;    //2
    

  37. }
    


  38. 


  39. 


  40. 

  41. void test_shared()
    

  42. {
    

  43.     string *s1 = new string("s1");
    


  44. 

  45.     shared_ptr<string> ps1(s1);
    

  46.     shared_ptr<string> ps2;
    

  47.     cout << ps1.unique() << endl;
    

  48.     cout << ps2.unique() << endl;
    

  49.     ps2 = ps1;
    


  50. 

  51.     cout << ps1.use_count()<<endl;    //2
    

  52.     cout<<ps2.use_count()<<endl;    //2
    

  53.     cout << ps1.unique()<<endl;    //0
    


  54. 

  55.     string *s3 = new string("s3");
    

  56.     shared_ptr<string> ps3(s3);
    


  57. 

  58.     cout << (ps1.get()) << endl;    //033AEB48
    

  59.     cout << ps3.get() << endl;    //033B2C50
    

  60.     cout << ps1.use_count() << endl;
    

  61.     cout << ps3.use_count() << endl;
    

  62.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  63.     cout << __LINE__ << "_ps3:" << *ps3 << endl;
    

  64.     cout << __LINE__ << "_ps2:" << *ps2 << endl;
    

  65.     swap(ps1, ps3);    //交换所拥有的对象
    

  66.     cout << (ps1.get())<<endl;    //033B2C50
    

  67.     cout << ps3.get() << endl;    //033AEB48
    

  68.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  69.     cout << __LINE__ << "_ps3:" << *ps3 << endl;
    

  70.     cout << ps1.use_count()<<endl;    //1
    

  71.     cout << ps2.use_count() << endl;    //2
    

  72.     ps2 = ps1;
    

  73.     cout << __LINE__ << "_ps2:" << *ps2 << endl;
    

  74.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  75.     cout << ps1.use_count()<<endl;    //2
    

  76.     cout << ps2.use_count() << endl;    //2
    

  77.     ps1.reset();    //放弃ps1的拥有权，引用计数的减少
    

  78.     cout << ps1.use_count()<<endl;    //0
    

  79.     cout << ps2.use_count()<<endl;    //1
    

  80. }
    


  81. 


  82. 

  83. int test2()
    

  84. {
    

  85.     //初始化方式1
    

  86.     std::unique_ptr<int> up1(new int(123));
    

  87.     //初始化方式2
    

  88.     std::unique_ptr<int> up2;
    

  89.     up2.reset(new int(456));
    

  90.     //初始化方式3 (-std=c++14)
    

  91.     std::unique_ptr<int> up3 = std::make_unique<int>(789);
    

  92.     cout << *up1 << " " << *up2 << " " << *up3 << endl;
    

  93. }
    


  94. 

  95. class Complex
    

  96. {
    

  97. public:
    

  98.         ~Complex(){cout << "_Destory_" << __LINE__ << endl;}
    


  99. 

  100.         Complex(int,int){cout << "_Creat_" << __LINE__ << endl;}
    

  101.         Complex(const Complex&){cout << "_Creat_cp_" << __LINE__ << endl;}
    

  102. };
    

  103. void Fun(Complex c1)
    

  104. {
    

  105. }
    

  106. Complex Fun2()
    

  107. {
    

  108.   Complex c(10,20);
    

  109.   return c;
    

  110. }
    

  111.  
    

  112. void test3()
    

  113. {
    

  114.         cout << "c1:" << endl;
    

  115.   Complex c1(1,2);
    

  116.   cout << "Fun(c1):" << endl;
    

  117.   Fun(c1);
    

  118.   cout << "c2:" << endl;
    

  119.   Complex c2 = Fun2();
    

  120.   cout << "c3:" << endl;
    

  121.   Complex &c3 = c2;
    

  122. }
    


  123. 

  124. int main()
    

  125. {
    

  126.         test3();
    

  127.         test2();
    

  128.         test_w();
    

  129.         //test_shared();
    

  130.         /*
    

  131.         unique_ptr<string> ps1, ps2;
    

  132.         ps1 = unique_ptr<string>(new string ("Hello"));
    

  133.         ps2 = move(ps1);
    

  134.         ps1 = unique_ptr<string>(new string ("nihao"));
    

  135.         cout << *ps2 << " " << *ps1 << endl;
    

  136.         */
    

  137.     return 0;
    

  138. }
    


  139.
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 楼主| keer_zu 发表于 2022-10-9 16:32 | 显示全部楼层
运行结果：

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  1. 

  2. zukeqiang@35fb9925ca21:~/test$ ./oz
    

  3. c1:
    

  4. _Creat_100
    

  5. Fun(c1):
    

  6. _Creat_cp_101
    

  7. _Destory_98
    

  8. c2:
    

  9. _Creat_100
    

  10. c3:
    

  11. _Destory_98
    

  12. _Destory_98
    

  13. 123 456 789
    

  14. 1
    

  15. 1
    

  16. 2
    

  17. 2
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 楼主| keer_zu 发表于 2022-10-9 16:44 | 显示全部楼层
例子做了修改：

复制
  1. #include <iostream>
    

  2. #include <memory>
    


  3. 

  4. using namespace std;
    


  5. 

  6. class B;    //声明
    

  7. class A
    

  8. {
    

  9. public:
    

  10.     shared_ptr<B> pb_;
    

  11.     ~A()
    

  12.     {
    

  13.         cout << "A delete\n";
    

  14.     }
    

  15. };
    


  16. 

  17. class B
    

  18. {
    

  19. public:
    

  20.     shared_ptr<A> pa_;
    

  21.     ~B()
    

  22.     {
    

  23.         cout << "B delete\n";
    

  24.     }
    

  25. };
    


  26. 

  27. void test_w()
    

  28. {
    

  29.     shared_ptr<B> pb(new B());
    

  30.     shared_ptr<A> pa(new A());
    

  31.     cout << pb.use_count() << endl;    //1
    

  32.     cout << pa.use_count() << endl;    //1
    

  33.     pb->pa_ = pa;
    

  34.     pa->pb_ = pb;
    

  35.     cout << pb.use_count() << endl;    //2
    

  36.     cout << pa.use_count() << endl;    //2
    

  37. }
    


  38. 


  39. 


  40. 

  41. void test_shared()
    

  42. {
    

  43.     string *s1 = new string("s1");
    


  44. 

  45.     shared_ptr<string> ps1(s1);
    

  46.     shared_ptr<string> ps2;
    

  47.     cout << ps1.unique() << endl;
    

  48.     cout << ps2.unique() << endl;
    

  49.     ps2 = ps1;
    


  50. 

  51.     cout << ps1.use_count()<<endl;    //2
    

  52.     cout<<ps2.use_count()<<endl;    //2
    

  53.     cout << ps1.unique()<<endl;    //0
    


  54. 

  55.     string *s3 = new string("s3");
    

  56.     shared_ptr<string> ps3(s3);
    


  57. 

  58.     cout << (ps1.get()) << endl;    //033AEB48
    

  59.     cout << ps3.get() << endl;    //033B2C50
    

  60.     cout << ps1.use_count() << endl;
    

  61.     cout << ps3.use_count() << endl;
    

  62.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  63.     cout << __LINE__ << "_ps3:" << *ps3 << endl;
    

  64.     cout << __LINE__ << "_ps2:" << *ps2 << endl;
    

  65.     swap(ps1, ps3);    //交换所拥有的对象
    

  66.     cout << (ps1.get())<<endl;    //033B2C50
    

  67.     cout << ps3.get() << endl;    //033AEB48
    

  68.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  69.     cout << __LINE__ << "_ps3:" << *ps3 << endl;
    

  70.     cout << ps1.use_count()<<endl;    //1
    

  71.     cout << ps2.use_count() << endl;    //2
    

  72.     ps2 = ps1;
    

  73.     cout << __LINE__ << "_ps2:" << *ps2 << endl;
    

  74.     cout << __LINE__ << "_ps1:" << *ps1 << endl;
    

  75.     cout << ps1.use_count()<<endl;    //2
    

  76.     cout << ps2.use_count() << endl;    //2
    

  77.     ps1.reset();    //放弃ps1的拥有权，引用计数的减少
    

  78.     cout << ps1.use_count()<<endl;    //0
    

  79.     cout << ps2.use_count()<<endl;    //1
    

  80. }
    


  81. 


  82. 

  83. int test2()
    

  84. {
    

  85.     //初始化方式1
    

  86.     std::unique_ptr<int> up1(new int(123));
    

  87.     //初始化方式2
    

  88.     std::unique_ptr<int> up2;
    

  89.     up2.reset(new int(456));
    

  90.     //初始化方式3 (-std=c++14)
    

  91.     std::unique_ptr<int> up3 = std::make_unique<int>(789);
    

  92.     cout << *up1 << " " << *up2 << " " << *up3 << endl;
    

  93. }
    


  94. 

  95. class Complex
    

  96. {
    

  97. private:
    

  98.     int Real;
    

  99.     int Image;
    


  100. 

  101. public:
    

  102.         ~Complex(){cout << "_Destory_" << __LINE__ << endl;}
    


  103. 

  104.         Complex(int r,int i):Real(r),Image(i){cout << "_Creat_" << __LINE__ << endl;}
    

  105.         Complex(const Complex& c):Real(c.Real),Image(c.Image){cout << "_Creat_cp_" << __LINE__ << endl;}
    

  106. };
    

  107. void Fun(Complex c1)
    

  108. {
    

  109. }
    

  110. Complex Fun2()
    

  111. {
    

  112.   Complex c(10,20);
    

  113.   return c;
    

  114. }
    

  115.  
    

  116. void test3()
    

  117. {
    

  118.         cout << "c1:" << endl;
    

  119.   Complex c1(1,2);
    

  120.   cout << "Fun(c1):" << endl;
    

  121.   Fun(c1);
    

  122.   cout << "c2:" << endl;
    

  123.   Complex c2 = Fun2();
    

  124.   cout << "c3:" << endl;
    

  125.   Complex &c3 = c2;
    

  126.   cout << "c4:" << endl;
    

  127.   Complex c4 = c3;
    

  128.   cout << "c5:" << endl;
    

  129.   Complex c5(c4);
    

  130.   cout << "c5 value:"  << endl; 
    

  131. }
    


  132. 

  133. int main()
    

  134. {
    

  135.         test3();
    

  136.         test2();
    

  137.         test_w();
    

  138.         //test_shared();
    

  139.         /*
    

  140.         unique_ptr<string> ps1, ps2;
    

  141.         ps1 = unique_ptr<string>(new string ("Hello"));
    

  142.         ps2 = move(ps1);
    

  143.         ps1 = unique_ptr<string>(new string ("nihao"));
    

  144.         cout << *ps2 << " " << *ps1 << endl;
    

  145.         */
    

  146.     return 0;
    

  147. }
    


  148.
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 楼主| keer_zu 发表于 2022-10-9 16:45 | 显示全部楼层
结果：

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  1. 

  2. zukeqiang@35fb9925ca21:~/test$ ./oz
    

  3. c1:
    

  4. _Creat_104
    

  5. Fun(c1):
    

  6. _Creat_cp_105
    

  7. _Destory_102
    

  8. c2:
    

  9. _Creat_104
    

  10. c3:
    

  11. c4:
    

  12. _Creat_cp_105
    

  13. c5:
    

  14. _Creat_cp_105
    

  15. c5 value:
    

  16. _Destory_102
    

  17. _Destory_102
    

  18. _Destory_102
    

  19. _Destory_102
    

  20. 123 456 789
    

  21. 1
    

  22. 1
    

  23. 2
    

  24. 2
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