c++:智能指针例子

实现一个strBlob类，通过智能指针，这个类的对象间共享数据data

//动态内存实例StrBlob
class StrBlob
{
public:
    typedef vector<string>::size_type size_type;
    StrBlob();
    StrBlob(initializer_list<string> il);
    size_type size() const { return data->size(); }
    bool empty() const { return data->empty(); }
    //添加删除元素
    void push_back(const string &t) { data->push_back(t); }
    void pop_back();
    //元素访问
    string &front();
    string &back();
    ~StrBlob();

private:
    // 智能指针对象
    shared_ptr<vector<string>> data;
    void check(size_type i, const string &msg) const;
};

// 默认构造函数，make_shared创建一个智能指针
StrBlob::StrBlob():data(make_shared<vector<string>>())
{
}

StrBlob::StrBlob(initializer_list<string> il): data(make_shared<vector<string>>(il))
{
}

void StrBlob::pop_back()
{
    check(0, "pop_back on empty StrBlob");
    data->pop_back();
}

string & StrBlob::front()
{
    check(0, "front on empty StrBlob");
    return data->front();
}

string & StrBlob::back()
{
    check(0, "back on empty StrBlob");
    return data->back();
}

StrBlob::~StrBlob()
{
}

void StrBlob::check(size_type i, const string & msg) const
{
    if (i >= data->size()) {
        throw out_of_range(msg);
    }
}

调用

int main()
{
    StrBlob b1;
    StrBlob b2 = { "a","an","the" };
    b1 = b2;
    b2.push_back("about");

    cout << "b1:" << b1.size();
    cout << "b2:" << b2.size();
    return 0;
}

输出都为4

动态内存

动态内存实现vector创建和读写

vector<int>* newVector() {
    vector<int> *vec=new vector<int>();
    return vec;
}

vector<int>* makeVector(vector<int>* vec) {
    int a;
    while(cin>>a)
    {
        vec->push_back(a);
    }
    return vec;
}

void getVector(vector<int>* vec) {
    for (vector<int>::iterator it = vec->begin(); it != vec->end(); it++)
        cout << *it << " ";    //使用迭代器，正确
    delete vec;
}

int main()
{
    getVector(makeVector(newVector()));
    return 0;
}

智能指针

不需要delete操作

shared_ptr<vector<int>> newVector() {
    shared_ptr<vector<int>> vec = make_shared<vector<int>>();
    return vec;
}

shared_ptr<vector<int>> makeVector(shared_ptr<vector<int>> vec) {
    int a;
    while(cin>>a)
    {
        vec->push_back(a);
    }
    return vec;
}

void getVector(shared_ptr<vector<int>> vec) {
    for (vector<int>::iterator it = vec->begin(); it != vec->end(); it++)
        cout << *it << " ";    //使用迭代器，正确
}

int main()
{
    getVector(makeVector(newVector()));
    return 0;
}