Implementations

#include<vector>
#include<string>
//Provision_26 : Postone variable definitions as long as possible

//如果定义还没用就抛出异常 需要：构造+析构

void AB() {
    class S
    {
    public:
        S() = default;
        S(const int& _i) :i(_i) {}
    private:
        std::string s;
        int i;
    };
    int f(int i);
    auto n = 100;
    S A;//method A: 1 构造 + 1 析构 + n 赋值
    for (int i = 0;i < n;++i)
    {
        A = S(i);
    }
    //method B : n 构造 + n 析构
    for (int i = 0;i < n;++i)
    {
        S B(f(i));
    }
}
//当 构造 + 析构  < 赋值 ：using B 变量A作用域也大

//Provision_27 Minimize casting
//避免使用 dynamic_cast

//问题：只有 base point 要执行 derived class member function
//解决： 在base class 中  virtual derived member function

class Window
{
public:
    virtual void blink() = 0;//闪烁
};
class SpecialWindow :public Window
{
public:
    virtual void blink() override
    {
        //....
    };
};

//Provision_31: Minimize compilation dependencies between files
//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
//解决1 ：(Handle classes)point to imolementation :将对象实现细节隐藏于一个指针背后

//Person.h

#pragma once
#include<string>
#include<memory>

class PersonImpl;
class Date;
class Address;

class Person
{
public:
    Person(const std::string& name, const Date& birthday, const Address& addr);
    std::string name() const;
    std::string birthday() const;
    std::string address() const;
private:
    std::shared_ptr<PersonImpl> pImpl;
};

//Person.cpp

#include"person.h"
#include"PersonImpl.h"

Person::Person(const std::string& name, const Date& birthday, const Address& addr)
    :pImpl(std::make_shared<PersonImpl>(name, birthday, addr)) {}
std::string Person::name() const
{
    return pImpl->name();
}
std::string Person::birthday() const
{
    return pImpl->birthday();
}
std::string Person::address() const
{
    return pImpl->address();
}

//PersonImpl.h

#pragma once
#include<string>
#include"Date.h"
#include"Address.h"
class PersonImpl
{
public:
    PersonImpl(const std::string& name, const Date& birthday, const Address& addr)
        :theName(name), theBirthday(birthday), theAddress(addr) {}
    std::string name() const;
    std::string birthday() const;
    std::string address() const;
private:
    std::string theName;
    Date theBirthday;
    Address theAddress;
};


//PersonImpl.cpp

#include"PersonImpl.h"
std::string
PersonImpl::name() const { return theName; }
std::string
PersonImpl::birthday() const { return theBirthday.date(); }
std::string
PersonImpl::address() const { return theAddress.addr(); }


//解决2: (Interface class)abstract base 接口在Person 细节在class RealPerson :public Person private
//使用：auto pp(Person::create(name,birthday,addr))

//person.h

class Person
{
public:
    virtual ~Person() {}
    virtual std::string name() const = 0;
    virtual std::string birthday() const = 0;
    virtual std::string address() const =0 ;

    static std::shared_ptr<Person> create(const std::string& name, const Date& birthday, const Address& addr);
};


//person,cpp

#include"Person.h"
#include"RealPerson.h"
std::shared_ptr<Person>
Person::create(const std::string& name, const Date& birthday, const Address& addr)
{
    return std::make_shared<Person>(RealPerson(name, birthday, addr));
}


//RealPerson

#pragma once
#include"person.h"
#include<string>
#include"Date.h"
#include"Address.h"

class RealPerson :public Person
{
public:
    RealPerson(const std::string& name, const Date& birthday, const Address& addr)
        :theName(name), theBirthday(birthday), theAddress(addr) {}
    virtual ~RealPerson() {}
    std::string name() const override;
    std::string birthday() const override;
    std::string address() const override;
private:
    std::string theName;
    Date theBirthday;
    Address theAddress;
};


//RealPerson.cpp

#include"PersonImpl.h"
std::string 
PersonImpl::name() const { return theName; }
std::string 
PersonImpl::birthday() const { return theBirthday.date(); }
std::string 
PersonImpl::address() const { return theAddress.addr(); }