简单的MyString类

这里好像有两个错误，一个是内存泄漏，还有一个是size，以后复习再改

#include<iostream>
#include<cstring>
using namespace std;

class Mystring{
public:
    Mystring(const char *a ="");             //构造函数
    Mystring(const Mystring &other);            //复制构造
    Mystring & operator =(const Mystring &fir); //复制赋值
    Mystring (Mystring &&other);                //移动构造
    Mystring & operator=(Mystring && other); // 移动赋值
    Mystring operator + (const Mystring &fir);  //+字符串连接
    Mystring TakeString(int i,int j);           //取子串函数,当前对象是母串
    char& operator[](int i);                    //重载下标运算符
    ~Mystring();                                //析构函数
    friend istream &operator>>(istream &in,Mystring &other);//输入
    friend ostream & operator<<(ostream &out, Mystring &other);//输出
private:
    int Long;//计长度
    char *A;//字符串
};

Mystring::Mystring(const char *a)   // 构造函数
{
    if (a == nullptr)
        a = "";  // 将空指针转化为空串
    A = new char[strlen(a) + 1];// 分配存储空间
    Long=strlen(a);
    strcpy(A, a);  // 复制串值
}

Mystring::Mystring(const Mystring &other)//复制构造函数
{
    A=new char[other.Long+1];
    Long=other.Long;
    strcpy(A,other.A);
}

Mystring&  Mystring::operator =(const Mystring &fir)//复制赋值
{
    if(this==&fir)
    {
        return *this;
    }
    else
    {
        delete []A;//避免内存泄漏，先释放原先申请的
        A=new char[fir.Long+1];
        strcpy(A,fir.A);
        Long=fir.Long;
        return *this;
    }
}

Mystring &Mystring:: operator=(Mystring && other)// 移动赋值
{
    char *t;//交换字符串
    t=A;
    A=other.A;
    other.A=t;
    int l;//交换长度
    l=Long;
    Long=other.Long;
    other.Long=l;
    return *this;
}

Mystring:: Mystring(Mystring &&other)//移动构造
{
        A = other.A;
        Long=other.Long;
        other.A = nullptr;
}

Mystring Mystring::operator+(const Mystring &fir)//连接函数
{
    Mystring newString;
    delete [] newString.A;
    newString.A=new char[this->Long+fir.Long+1];//接着再申请一个要加入的字符串的长度
    newString.Long=this->Long+fir.Long;
    strcpy(newString.A,this->A);
    strcat(newString.A,fir.A);
    return newString;
}

Mystring Mystring::TakeString(int i,int j)//取子串函数,当前对象是母串
{
    Mystring result;
    delete []result.A;
    result.Long=j;
    result.A=new char[result.Long+1];
    strncpy(result.A,A+i,j);
    return result;
}

char& Mystring::operator[](int i)
{
    if( i > Long )
    {
        cout<<"查询不到"<<endl;
    }
    return *(A+i);
}

ostream& operator<<(ostream &out, Mystring &other)
{
    out<<other.A;
    return out;
}

istream &operator>>(istream &in,Mystring &other)
{
    char t[200];
    in>>t;
    other.Long=strlen(t);
    other.A=new char[other.Long+1];
    strcpy(other.A,t);
    return in;
}

Mystring::~Mystring()//好像这里的处理不是很好
{
    //cout<<"xigou"<<endl;
    if(A!=nullptr)
    {
        delete []A;
        A=nullptr;
    }
}

int main()
{
    /*Mystring first(" best it");
    cout<<first[3]<<endl;下标运算符重载的测试
    Mystring a("ok");
    Mystring b,c;
    c=a+b;
    cout<<a<<b<<c;*/
    Mystring S[4];
    char p;
    int i,j,k,l;
    cin>>S[0]>>S[1];
    while(cin>>p)
    {
        switch(p)
        {
        case 'P':
            cin>>i;
            cout<<S[i-1]<<endl;
            break;
        case 'A':
            cin>>i>>j;
            S[j-1]=S[i-1];
            break;
        case 'C':
            cin>>i>>j>>k;
            S[k-1]=S[i-1]+S[j-1];
            break;
        case 'F':
            cin>>i>>j>>k>>l;
            S[l-1]=S[i-1].TakeString(j,k);
            break;
        }
    }
    return 0;
}