c++ - 获取线路如何工作？

Question

我正在尝试编写自己的 getline 函数，但它一直出现段错误。如果我的无法正常工作，我该如何修复它以及 get line 如何正式工作？我写这篇文章是为了学习如何更好地编码。

#include"MyString.h"





MyString::MyString( )  //constructor
{
    size=0;
    capacity=1;
    data=new char[capacity];

}
MyString::MyString(char * n)  //copy constructor
{
    size=strlen(n);
    capacity=strlen(n)+1;
    data=new char[capacity];
    strcpy(data,n);
}
MyString::MyString(const MyString &right)  //
{
    size=strlen(right.data);
    capacity=strlen(right.data)+1;
    data=new char [capacity];
    strcpy(data,right.data);

}
MyString::~MyString( )
{
    delete [] data;
}
MyString  MyString::operator = (const MyString& s)
{

    if(this!=&s)
    {
        MyString temp=data;
        delete [] data;
        size=strlen(s.data);
        capacity=size+1;
        data= new char [capacity];
        strcpy(data,s.data);
    }
}
MyString&  MyString::append(const MyString& s)
{
    if(this!=&s)
    {
        strcat(data,s.data);
    }


}
MyString&  MyString::erase()
{

}
MyString  MyString::operator + (const MyString& s)const
{
    return strcat(data,s.data);
}
bool  MyString::operator == (const MyString& s)
{
    return strcmp(data,s.data)==0;
}
bool  MyString::operator <  (const MyString& s)
{
    return strcmp(data,s.data)<0;
}
bool  MyString::operator >  (const MyString& s)
{
    return strcmp(data,s.data)>0;
}
bool  MyString::operator <= (const MyString& s)
{
    return strcmp(data,s.data)<=0;
}
bool  MyString::operator >= (const MyString& s)
{
    return strcmp(data,s.data)>=0;
}
bool  MyString::operator != (const MyString& s)
{
    return strcmp(data,s.data)!=0;
}
void  MyString::operator += (const MyString& s)
{
    append(s.data);
}
char&  MyString::operator [ ] (int n)
{
    return data[n];
}
void  MyString::getline(istream& in)
{
    char c;
    erase();
    ifstream input;
    while(in.get(c)&&c!='\n')
    {
        data[size]=c;
        size++;

        if(size+1<=capacity)
        {
          capacity*=2;
          char*p=new char[capacity];
          strcpy(p,data);
          delete [] data;
          data=p;
        }
        data[size]=c;
        size++;
        data[size]='\0';
    }

}
int  MyString::length( ) const
{
    return strlen(data);
}
void MyString::grow()
{
 capacity=strlen(data)+1;
MyString temp;
temp=data;
delete [] data;
capacity*=2;
data= new char[capacity];
}

ostream& operator<<(ostream& out, MyString& s)
{

    out<<s.data;
    return out;


}



// int  MyString::getCapacity(){return capacity;}

Answer 1

嗯...

if(size+1<=capacity)

假设您的容量为 11，尺寸为 11。

if( 12 <= 11 )
{
   // Resize capacity.  This code won't run.
}

你想要 if( size >= capacity )。

此外，您有 data[size] = c; size++; 在你的循环中两次。所以你要为每个角色制作 2 个拷贝。