OurString& OurString::operator=(const OurString& str) { if (this == &str) return *this; if(ptr != NULL) { delete [] ptr; } ptr = new char[str.len + 1]; assert(ptr != 0); ptr = strcpy(ptr, str.ptr); len = str.len; return *this; } 你可以把上述的参数改成const char *str吗

可以修改参数为`const char* str`，但是在代码中需要修改一些地方。由于现在的参数类型是指向字符数组的指针，我们不能像之前那样使用`str.len`，因为指针没有`len`属性。我们需要在代码中添加一行来计算字符串长度，例如使用`strlen(str)`函数来获取字符串的长度。修改后的代码如下：

OurString& OurString::operator=(const char* str) {
    if (ptr != NULL) {
        delete[] ptr;
    }
    len = strlen(str);
    ptr = new char[len + 1];
    assert(ptr != 0);
    ptr = strcpy(ptr, str);
    return *this;
}

需要注意的是，在这个函数中我们没有检查`str`是否为空指针。如果`str`是空指针，那么调用`strlen(str)`函数将会导致程序崩溃。因此，在实际使用中，我们需要在函数开头添加一行代码来检查`str`是否为空指针。

相关问题

填充下面这个程序中所有出现// TODO: fill the code这个任务的地方#include <iostream> #include <cstring> #include "ourstring.h" #include "strlib.h" using namespace std; OurString::OurString(){ // TODO: fill the code } OurString::OurString(const char *str){ // TODO: fill the code } OurString::OurString(const OurString &dstr){ // TODO: fill the code } OurString::~OurString(){ // TODO: fill the code } string OurString::toString() const{ // TODO: fill the code } OurString OurString::subStr(unsigned int start, unsigned int n) const{ // TODO: fill the code } bool OurString::operator > (const OurString &dstr) const{ // TODO: fill the code } bool OurString::operator < (const OurString &dstr) const{ // TODO: fill the code } bool OurString::operator == (const OurString &dstr) const{ // TODO: fill the code } unsigned int OurString::length () const{ // TODO: fill the code } const OurString& OurString::operator = (const OurString &dstr){ // TODO: fill the code } const OurString& OurString::operator = (const char *str){ // TODO: fill the code } char& OurString::operator[](int index){ // TODO: fill the code } const OurString OurString::operator + (const OurString &dstr) const{ // TODO: fill the code } const OurString OurString::operator + (const char *str) const{ // TODO: fill the code } const OurString& OurString::operator += (const OurString &dstr){ // TODO: fill the code } const OurString& OurString::operator += (const char *str){ // TODO: fill the code } ostream & operator<<(ostream &os, const OurString &dstr){ // TODO: fill the code } istream & operator>>(istream &is, OurString &dstr){ // TODO: fill the code }

好的，下面是填充后的代码，每个 TODO 已经被替换成相应的实现：

#include <iostream>
#include <cstring>
#include "ourstring.h"
#include "strlib.h"
using namespace std;

OurString::OurString(){
    str = new char[1];
    str[0] = '\0';
}

OurString::OurString(const char *str){
    this->str = new char[strlen(str)+1];
    strcpy(this->str, str);
}

OurString::OurString(const OurString &dstr){
    this->str = new char[dstr.length()+1];
    strcpy(this->str, dstr.str);
}

OurString::~OurString(){
    delete [] str;
}

string OurString::toString() const{
    return string(str);
}

OurString OurString::subStr(unsigned int start, unsigned int n) const{
    if (start >= length()) return OurString();
    n = (n > length() - start) ? length() - start : n;
    return OurString(str + start, str + start + n);
}

bool OurString::operator > (const OurString &dstr) const{
    return strcmp(str, dstr.str) > 0;
}

bool OurString::operator < (const OurString &dstr) const{
    return strcmp(str, dstr.str) < 0;
}

bool OurString::operator == (const OurString &dstr) const{
    return strcmp(str, dstr.str) == 0;
}

unsigned int OurString::length () const{
    return strlen(str);
}

const OurString& OurString::operator = (const OurString &dstr){
    if (this != &dstr) {
        delete [] str;
        str = new char[dstr.length()+1];
        strcpy(str, dstr.str);
    }
    return *this;
}

const OurString& OurString::operator = (const char *str){
    if (this->str != str) {
        delete [] this->str;
        this->str = new char[strlen(str)+1];
        strcpy(this->str, str);
    }
    return *this;
}

char& OurString::operator[](int index){
    return str[index];
}

const OurString OurString::operator + (const OurString &dstr) const{
    OurString s;
    s.str = new char[length() + dstr.length() + 1];
    strcpy(s.str, str);
    strcat(s.str, dstr.str);
    return s;
}

const OurString OurString::operator + (const char *str) const{
    OurString s;
    s.str = new char[length() + strlen(str) + 1];
    strcpy(s.str, this->str);
    strcat(s.str, str);
    return s;
}

const OurString& OurString::operator += (const OurString &dstr){
    *this = *this + dstr;
    return *this;
}

const OurString& OurString::operator += (const char *str){
    *this = *this + str;
    return *this;
}

ostream & operator<<(ostream &os, const OurString &dstr){
    os << dstr.str;
    return os;
}

istream & operator>>(istream &is, OurString &dstr){
    string s;
    is >> s;
    dstr = s.c_str();
    return is;
}

bool String::operator == (const char* s)const {return (strcmp(m_str,s ? s : "") == 0);}

这是一个字符串类中的重载运算符==，用于判断当前对象和传入的C风格字符串是否相等。具体实现是调用了C标准库函数strcmp()，比较当前对象的m_str成员和传入的s指针指向的字符串是否相等。如果相等返回0，否则返回非0值。需要注意的是，为了避免传入的s指针为NULL，代码中使用了三目运算符将其转为空字符串。