说明

StrBlob拷贝构造函数的合成版本拷贝指向vector容器的shared_ptr

实现

Copy 1#include <iostream>
 2#include <vector>
 3#include <string>
 4#include <initializer_list>
 5#include <memory>
 6
 7using std::cout;
 8using std::endl;
 9using std::initializer_list;
10using std::make_shared;
11using std::ostream;
12using std::shared_ptr;
13using std::string;
14using std::vector;
15
16class StrBlob
17{
18    friend ostream &operator<<(ostream &os, const StrBlob &sb);
19public:
20    typedef vector<string>::size_type size_type;
21    StrBlob();
22    StrBlob(initializer_list<string> il);
23    // 使用合成的拷贝构造函数和拷贝赋值运算符
24    size_type size() const { return data->size(); }
25    bool empty() const { return data->empty(); }
26    void push_back(const string &t) { data->push_back(t); }
27    void pop_back();
28    string &front();
29    string &back();
30private:
31    shared_ptr<vector<string>> data;
32    void check(size_type i, const string &msg) const;
33};
34
35// 创建一个StrBlob对象，为data申请内存
36StrBlob::StrBlob() : data(make_shared<vector<string>>()) { }
37
38// 创建一个StrBlob对象，为data申请内存并初始化
39StrBlob::StrBlob(initializer_list<string> il): data(make_shared<vector<string>>(il)) { }
40
41// 检查给定位置的有效性
42void StrBlob::check(size_type i, const string &msg) const
43{
44    if (i >= data->size())
45        throw std::out_of_range(msg);
46}
47
48// 若容器不空: 返回首元素或者尾元素，删除尾元素
49string& StrBlob::front()
50{
51    check(0, "front on empty StrBlob");
52    return data->front();
53}
54string& StrBlob::back()
55{
56    check(0, "back on empty StrBlob");
57    return data->back();
58}
59void StrBlob::pop_back()
60{
61    check(0, "pop_back on empty StrBlob");
62    data->pop_back();
63}
64
65ostream &operator<<(ostream &os, const StrBlob &sb)
66{
67    for (const string &s : *(sb.data))
68        os << s << "\t";
69    return os;
70}
71
72int main()
73{
74    StrBlob sb{"Hat", "Shoe"}, sb2 = sb;
75    cout << sb2 << endl;
76
77    sb.pop_back();
78    cout << sb2 << endl;
79
80    return 0;
81}

输出

Hat	Shoe
Hat