1 #include<vector>
2 #include<string>
3 //Provision_26 : Postone variable definitions as long as possible
4
5 //如果定义还没用就抛出异常 需要：构造+析构
6
7 void AB() {
8 class S
9 {
10 public:
11 S() = default;
12 S(const int& _i) :i(_i) {}
13 private:
14 std::string s;
15 int i;
16 };
17 int f(int i);
18 auto n = 100;
19 S A;//method A: 1 构造 + 1 析构 + n 赋值
20 for (int i = 0;i < n;++i)
21 {
22 A = S(i);
23 }
24 //method B : n 构造 + n 析构
25 for (int i = 0;i < n;++i)
26 {
27 S B(f(i));
28 }
29 }
30 //当 构造 + 析构 < 赋值 ：using B 变量A作用域也大
31
32 //Provision_27 Minimize casting
33 //避免使用 dynamic_cast
34
35 //问题：只有 base point 要执行 derived class member function
36 //解决： 在base class 中 virtual derived member function
37
38 class Window
39 {
40 public:
41 virtual void blink() = 0;//闪烁
42 };
43 class SpecialWindow :public Window
44 {
45 public:
46 virtual void blink() override
47 {
48 //....
49 };
50 };
51
52 //Provision_31: Minimize compilation dependencies between files
53 //问题：class private成员往往依赖头文件(#include"Tree_Note.h") 若头文件修改则导致所有依赖该头文件的实现(Tree_Note type)都重新编译
54 //解决1 ：(Handle classes)point to imolementation :将对象实现细节隐藏于一个指针背后
55
56 //Person.h
57
58 #pragma once
59 #include<string>
60 #include<memory>
61
62 class PersonImpl;
63 class Date;
64 class Address;
65
66 class Person
67 {
68 public:
69 Person(const std::string& name, const Date& birthday, const Address& addr);
70 std::string name() const;
71 std::string birthday() const;
72 std::string address() const;
73 private:
74 std::shared_ptr<PersonImpl> pImpl;
75 };
76
77 //Person.cpp
78
79 #include"person.h"
80 #include"PersonImpl.h"
81
82 Person::Person(const std::string& name, const Date& birthday, const Address& addr)
83 :pImpl(std::make_shared<PersonImpl>(name, birthday, addr)) {}
84 std::string Person::name() const
85 {
86 return pImpl->name();
87 }
88 std::string Person::birthday() const
89 {
90 return pImpl->birthday();
91 }
92 std::string Person::address() const
93 {
94 return pImpl->address();
95 }
96
97 //PersonImpl.h
98
99 #pragma once
100 #include<string>
101 #include"Date.h"
102 #include"Address.h"
103 class PersonImpl
104 {
105 public:
106 PersonImpl(const std::string& name, const Date& birthday, const Address& addr)
107 :theName(name), theBirthday(birthday), theAddress(addr) {}
108 std::string name() const;
109 std::string birthday() const;
110 std::string address() const;
111 private:
112 std::string theName;
113 Date theBirthday;
114 Address theAddress;
115 };
116
117
118 //PersonImpl.cpp
119
120 #include"PersonImpl.h"
121 std::string
122 PersonImpl::name() const { return theName; }
123 std::string
124 PersonImpl::birthday() const { return theBirthday.date(); }
125 std::string
126 PersonImpl::address() const { return theAddress.addr(); }
127
128
129 //解决2: (Interface class)abstract base 接口在Person 细节在class RealPerson :public Person private
130 //使用：auto pp(Person::create(name,birthday,addr))
131
132 //person.h
133
134 class Person
135 {
136 public:
137 virtual ~Person() {}
138 virtual std::string name() const = 0;
139 virtual std::string birthday() const = 0;
140 virtual std::string address() const =0 ;
141
142 static std::shared_ptr<Person> create(const std::string& name, const Date& birthday, const Address& addr);
143 };
144
145
146 //person,cpp
147
148 #include"Person.h"
149 #include"RealPerson.h"
150 std::shared_ptr<Person>
151 Person::create(const std::string& name, const Date& birthday, const Address& addr)
152 {
153 return std::make_shared<Person>(RealPerson(name, birthday, addr));
154 }
155
156
157 //RealPerson
158
159 #pragma once
160 #include"person.h"
161 #include<string>
162 #include"Date.h"
163 #include"Address.h"
164
165 class RealPerson :public Person
166 {
167 public:
168 RealPerson(const std::string& name, const Date& birthday, const Address& addr)
169 :theName(name), theBirthday(birthday), theAddress(addr) {}
170 virtual ~RealPerson() {}
171 std::string name() const override;
172 std::string birthday() const override;
173 std::string address() const override;
174 private:
175 std::string theName;
176 Date theBirthday;
177 Address theAddress;
178 };
179
180
181 //RealPerson.cpp
182
183 #include"PersonImpl.h"
184 std::string
185 PersonImpl::name() const { return theName; }
186 std::string
187 PersonImpl::birthday() const { return theBirthday.date(); }
188 std::string
189 PersonImpl::address() const { return theAddress.addr(); }