我只是在试验并制作自己的字符串类。 (主要是因为我想在自定义方法中构建一些东西,例如“toBase64”等。无论如何,我想知道在使用 &String[0] 时如何访问 char* 的私有(private)成员。
我认为您可以使用运算符重载,但我目前只有它,因为 String[0] 返回 char*。 (我知道 & 是指针运算符)。
字符串.h
namespace CoffeeBeans
{
class _declspec(dllexport) Coffee_String
{
char* String;
int StringLength;
public:
Coffee_String();
Coffee_String(LPCSTR CString);
LPSTR operator[](int);
~Coffee_String();
};
}
字符串.cpp
#include "stdafx.h"
#include "String.h"
#include <Windows.h>
CoffeeBeans::Coffee_String::Coffee_String() {
this->String = nullptr;
this->StringLength = 0;
}
CoffeeBeans::Coffee_String::~Coffee_String() {
if (String != nullptr) {
delete[] this->String;
this->String = nullptr;
this->StringLength = 0;
}
}
CoffeeBeans::Coffee_String::Coffee_String(LPCSTR CString) {
int StringLength = strlen(CString) + 1;
this->String = new char[StringLength]();
this->StringLength = StringLength - 1;
memcpy_s(this->String, StringLength, CString, StringLength);
}
LPSTR CoffeeBeans::Coffee_String::operator[](int)
{
return this->String;
}
main.cpp
case WM_CREATE:{
CoffeeBeans::Coffee_String String("Test");
//I want to be able to do
//strcpy_s(&String[0], 3, "hi"); //Copy "hi" into the private variable char*String.
//I know this isn't a practical use, I wanted quick example (I would really pass it to recv (WinSock2))
MessageBeep(0);
break;
}
最佳答案
您的 operator[]
返回了错误的值。为了让&String[index]
访问正确的内存地址,operator[]
需要返回指定索引处字符的引用,而不是返回字符串指针本身,正如您目前所做的那样。
如果您查看 std::string::operator[]
的实际声明,您会看到它返回一个 std::string::reference
(又名 char &
) 或 std::string::const_reference
(又名 const char &
)(取决于它是否在非-const 或 const std::string
对象)。
尝试更像这样的东西:
字符串.h
namespace CoffeeBeans
{
class _declspec(dllexport) Coffee_String
{
char* String;
int StringLength;
public:
Coffee_String();
Coffee_String(const Coffee_String &src);
Coffee_String(const char *src);
~Coffee_String();
char& operator[](int index);
const char& operator[](int index) const;
Coffee_String& operator=(const Coffee_String &rhs);
};
};
字符串.cpp
#include "stdafx.h"
#include "String.h"
#include <algorithm>
#include <cstring>
CoffeeBeans::Coffee_String::Coffee_String() {
String = nullptr;
StringLength = 0;
}
CoffeeBeans::Coffee_String::Coffee_String(const CoffeeBeans::Coffee_String &src) {
StringLength = src.StringLength;
String = new char[StringLength+1];
std::copy(src.String, src.String+StringLength, String);
String[StringLength] = 0;
}
CoffeeBeans::Coffee_String::Coffee_String(const char *src) {
StringLength = std::strlen(str);
String = new char[StringLength+1];
std::copy(src, src+StringLength, String);
String[StringLength] = 0;
}
CoffeeBeans::Coffee_String::~Coffee_String() {
delete[] String;
String = nullptr;
StringLength = 0;
}
char& CoffeeBeans::Coffee_String::operator[](int index)
{
return String[index];
}
const char& CoffeeBeans::Coffee_String::operator[](int index) const
{
return String[index];
}
CoffeeBeans::Coffee_String& CoffeeBeans::Coffee_String::operator=(const CoffeeBeans::Coffee_String &rhs);
{
Coffee_String temp(rhs);
std::swap(String, temp.String);
std::swap(StringLength, temp.String);
return *this;
}
main.cpp
case WM_CREATE: {
CoffeeBeans::Coffee_String String("Test");
strcpy_s(&String[0], 3, "hi"); //Copy "hi" into the private variable char *String...
// note that the content of String will become "hi\0t\0", not "hi\0"
// and StringLength will still be 4...
MessageBeep(0);
break;
}
关于C++ - 在类上使用 &String[0] 访问 char*,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40412684/