临时对象专题
学习临时对象时的相关代码：
例1：
1 /*
2 *第一种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B b)
41 {
42 return b;
43 }
44
45 void main()
46 {
47 B t1 = Func(5);
48 }
49
50 //Out put
51 /*
52 Construct By: 0x0012FF20 5 //隐式类型转换构建临时对象
53 Copy Construct 0x0012FF7C 0x0012FF20 //拷贝构造函数进行传参(b = 临时对象)
54 Destructed 0x0012FF20 5 //摧毁临时对象
55 Destructed 0x0012FF7C 5 //摧毁对象t1
56 */
例2：
1 /*
2 *第二种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B b)
41 {
42 return b;
43 }
44
45 void main()
46 {
47 B t1;
48 t1 = Func(5);
49 }
50
51 //Out put
52 /*
53 Default Construct: 0012FF58 //默认构造创建t1
54 Construct By: 0012FE5C 5 //隐式类型转换创建临时对象
55 Copy Construct 0012FE8C 0012FE5C //拷贝构造函数传参(b=临时对象)
56 Destructed 0012FE5C 5 //摧毁临时对象
57 operator= 0012FF58 0012FE8C//赋值函数进行赋值（t1=b）
58 Destructed 0012FE8C 5 //摧毁对象b
59 Destructed 0012FF58 5 //摧毁对象t1
60 */
例3：
1 /*
2 *第三种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B b)
41 {
42 return b;
43 }
44
45 void main()
46 {
47 B t1(1);
48 t1 = Func(t1);
49 }
50
51 //Out put
52 /*
53 Construct By: 0012FF58 1 //构造函数创建t1
54 Copy Construct 0012FE5C 0012FF58 //拷贝构造创建临时对象
55 Copy Construct 0012FE8C 0012FE5C //拷贝构造函数进行传参(构建对象b)
56 Destructed 0012FE5C 1 //摧毁临时对象
57 operator= 0012FF58 0012FE8C //赋值函数进行赋值(t1=b)
58 Destructed 0012FE8C 1 //摧毁对象b
59 Destructed 0012FF58 1 //摧毁对象t1
60 */
例4：
1 /*
2 *第四种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B b)
41 {
42 return b;
43 }
44
45 void main()
46 {
47 B t1(1);
48 B t2 = Func(t1);
49 }
50
51 //Out put
52 /*
53 Construct By: 0012FF58 1 //构造函数创建对象t1
54 Copy Construct 0012FE60 0012FF58 //拷贝构造函数创建临时对象
55 Copy Construct 0012FF4C 0012FE60 //拷贝构造函数传参(b=t1)
56 Destructed 0012FE60 1 //摧毁临时对象
57 Destructed 0012FF4C 1 //摧毁对象b
58 Destructed 0012FF58 1 //摧毁对象t1
59 */
例5：
1 /*
2 *第五种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B &b)
41 {
42 return b;
43 }
44 void main()
45 {
46 B t1(1);
47 B t2 = Func(t1);
48 }
49
50 //Out put
51 /*
52 Construct By: 0012FF58 1 //构造函数创建对象t1
53 Copy Construct 0012FF4C 0012FF58 //拷贝构造函数进行赋值(t2=b)
54 Destructed 0012FF4C 1 //摧毁对象t2
55 Destructed 0012FF58 1 //摧毁对象t1
56 */
例6：
1 /*
2 *第六种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B & Func(B b)
41 {
42 return b;
43 }
44 void main()
45 {
46 B t1 = 5;
47 B t2 = Func(t1);
48 }
49
50 //Out put
51 /*
52 Construct By: 0012FF58 5 //隐式类型转换创建对象t1
53 Copy Construct 0012FE60 0012FF58 //拷贝构造创建临时对象
54 Destructed 0012FE60 5 //摧毁临时对象
55 Copy Construct 0012FF4C 0012FE60 //拷贝构造函数进行赋值(t2 = b)
56 Destructed 0012FF4C 1244768 //摧毁对象t2 //注意这个特殊启示
57 Destructed 0012FF58 5 //摧毁对象t1
58 */
例7：
1 /*
2 *第七种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B & Func(B b)
41 {
42 B t(3);
43 return t;
44 }
45
46 void main()
47 {
48 B t1(1);
49 B t2(5);
50 t2 = Func(t1);
51 }
52
53 //Out put
54 /*
55 Construct By :0012FF58 1 //构造函数创建对象t1
56 Construct By :0012FF4C 5 //构造函数创建对象t2
57 Copy Construct 0012FE60 0012FF58 //拷贝构造函数创建临时对象
58 Construct By :0012FE44 3 //构造函数创建对象t
59 Destructed 0012FE44 3 //摧毁对象t
60 Destructed 0012FE60 1 //摧毁临时对象
61 operator= 0012FF4C 0012FE44 //拷贝构造函数进行赋值(t2=t)
62 Destructed 0012FF4C -858993460 //摧毁对象t2
63 Destructed 0012FF58 1 //摧毁对象t1
64 */
例8：
1 /*
2 *第八种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 // B &operator=(const B &obj)
24 // {
25 // if(this!=&obj)
26 // {
27 // cout<<" operator= "<<this<<" "<<&obj<<endl;
28 // data=obj.data;
29 // }
30 // return *this;
31 // }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B & Func(B b)
41 {
42 B t(3);
43 return t;
44 }
45
46 void main()
47 {
48 B t1(1);
49 B t2(5);
50 t2 = Func(t1); //?? 有无赋值函数的区别
51 }
52
53 //Out put
54 /*
55 Construct By :0012FF58 1 //构造函数创建对象t1
56 Construct By :0012FF4C 5 //构造函数创建对象t2
57 Copy Construct 0012FE60 0012FF58 //拷贝构造函数创建临时对象
58 Construct By :0012FE44 3 //构造函数创建对象t
59 Destructed 0012FE44 3 //摧毁对象t
60 Destructed 0012FE60 1 //摧毁临时对象
61 Destructed 0012FF4C 3 //摧毁对象t2
62 Destructed 0012FF58 1 //摧毁对象t1
63 */
例9：
1 /*
2 *第九种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B &b)
41 {
42 B t3(b);
43 return t3;
44 }
45 void main()
46 {
47 B t1=5;
48 B t2=Func(t1);
49 }
50
51 //Out put //分步解析
52 /*
53 Construct By: 0012FF58 5 //隐式类型转换创建对象t1
54 Copy Construct 0012FE54 0012FF58 //拷贝构造函数创建临时对象
55 Copy Construct 0012FF4C 0012FE54 //拷贝构造函数创建局部对象t3
56 Destructed 0012FE54 5 //摧毁临时对象
57 Destructed 0012FF4C 5 //摧毁局部对象t3
58 Destructed 0012FF58 5 //摧毁对象t1
59 */
例10：
1 /*
2 *第十种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B Func(B &b)
41 {
42 B t3(b);
43 return t3;
44 }
45 void main()
46 {
47 B t1 = 5;
48 B t2;
49 t2 = Func(t1);
50 }
51
52 //Out put
53 /*
54 Construct By: 0012FF58 5 //隐式类型转换创建对象t1
55 Default Construct: 0012FF4C//默认创建对象t2
56 Copy Construct 0012FE40 0012FF58 //拷贝构造函数创建局部对象t3
57 Copy Construct 0012FE80 0012FE40 //拷贝构造函数创建临时对象
58 Destructed 0012FE40 5 //函数结束摧毁对象t3
59 operator= 0012FF4C 0012FE80 //赋值函数进行赋值(t2=临时对象)
60 Destructed 0012FE80 5 //摧毁临时对象
61 Destructed 0012FF4C 5 //摧毁对象t2
62 Destructed 0012FF58 5 //摧毁对象t1
63 */
例11：
1 /*
2 *第十一种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B & Func(B &b)
41 {
42 B t3(b);
43 return t3;
44 }
45 void main()
46 {
47 B t1 = 5;
48 B t2;
49 t2 = Func(t1);
50 }
51
52 //Out put
53 /*
54 Construct By: 0012FF58 5 //隐式类型转换构建对象t1
55 Default Construct: 0012FF4C //默认构造函数构建对象t2
56 Copy Construct 0012FE64 0012FF58 //拷贝构造函数创建局部对象t3
57 Destructed 0012FE64 5 //函数结束摧毁局部对象t3
58 operator= 0012FF4C 0012FE64 //赋值函数进行赋值(t2=局部对象)
59 Destructed 0012FF4C 1245004 //摧毁对象t2 //? ?
60 Destructed 0012FF58 5 //摧毁对象t1
61 */
例12：
1 /*
2 *第十二种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 B & Func(B &b)
41 {
42 B t3(b);
43 return t3;
44 }
45 void main()
46 {
47 B t1(5);
48 B t2 = Func(t1);
49 }
50
51 //Out put
52 /*
53 Construct By: 0012FF58 5 //构造函数创建对象t1
54 Copy Construct 0012FE64 0012FF58 //拷贝构造函数创建局部对象t3
55 Destructed 0012FE64 5 //摧毁局部对象t3
56 Copy Construct 0012FF4C 0012FE64 //拷贝构造函数进行赋值(t2=t3)
57 Destructed 0012FF4C 1245004 //摧毁对象t2 //? 思考
58 Destructed 0012FF58 5 //摧毁对象t1
59 */
例13：综合运用类中函数的示范程序：
1 /*
2 *第十三种情况：分步解析
3 */
4 #include<iostream>
5 using namespace std;
6
7 class B
8 {
9 public:
10 B()
11 {
12 cout<<"Default Construct"<<" "<<this<<endl;
13 }
14 B(int i):data(i)
15 {
16 cout<<"Construct By: "<<this<<" "<<data<<endl;
17 }
18 B(const B &b)
19 {
20 cout<<"Copy Construct"<<" "<<this<<" "<<&b<<endl;
21 data = b.data;
22 }
23 B &operator=(const B &obj)
24 {
25 if(this!=&obj)
26 {
27 cout<<" operator= "<<this<<" "<<&obj<<endl;
28 data=obj.data;
29 }
30 return *this;
31 }
32 ~B()
33 {
34 cout<<"Destructed"<<" "<<this<<" "<<data<<endl;
35 }
36 private:
37 int data;
38 };
39
40 void Func(B &b)
41 {
42 B t3(b);
43 }
44
45 void main()
46 {
47 cout<<"B t1执行结果:"<<endl;
48 B t1;
49 cout<<"B t2(5)执行结果:"<<endl;
50 B t2(5);
51 cout<<"B t3(t2)执行结果:"<<endl;
52 B t3(t2);
53 cout<<"B t4=6执行结果:"<<endl;
54 B t4=6;
55 cout<<"B t5=t4执行结果:"<<endl;
56 B t5=t4;
57 cout<<"B t6执行结果:"<<endl;
58 B t6;
59 cout<<"t6 = t5执行结果:"<<endl;
60 t6=t5;
61 cout<<"Func(t6)执行结果:"<<endl;
62 Func(t6);
63 }
64
65 //Out put
66 /*
67 B t1执行结果:
68 Default Construct: 0x0012FF70
69 B t2(5)执行结果:
70 Construct By: 0x0012FF6C 5
71 B t3(t2)执行结果:
72 Copy Construct 0x0012FF68 0x0012FF6C
73 B t4=6执行结果:
74 Construct By: 0x0012FF64 6 //饮食类型转换
75 B t5=t4执行结果:
76 Copy Construct 0x0012FF60 0x0012FF64
77 B t6执行结果:
78 Default Construct: 0x0012FF5C
79 t6 = t5执行结果:
80 operator= 0x0012FF5C 0x0012FF60
81 Func(t6)执行结果:
82 Copy Construct 0x0012FF00 0x0012FF5C
83 Destructed 0x0012FF00 6 //摧毁局部对象t3
84 Destructed 0x0012FF5C 6 //摧毁局部对象t6
85 Destructed 0x0012FF60 6 //摧毁局部对象t5
86 Destructed 0x0012FF64 6 //摧毁局部对象t4
87 Destructed 0x0012FF68 5 //摧毁局部对象t3
88 Destructed 0x0012FF6C 5 //摧毁局部对象t2
89 Destructed 0x0012FF70 0 //摧毁局部对象t1
90 */
备注：前十二种示例完全可以说明传参与返回时，使用值与引用的区别。后一种主要解释一下类中函数的使用情况，在不同的情况下的调用区别。
