string.erase 函数在特定情况下不起作用

Question

我有以下格式的字符串："name.bag.csv" 我想从字符串中删除“.bag”。这是我尝试运行:

的代码示例

csv_file_name = "loololololool.bag.csv";
csv_file_name.erase(csv_file_name.end()-8, 4);
std::cout << csv_file_name << std::endl;

但是我在第二行收到一个错误:

 no matching function for call to ‘std::__cxx11::basic_string<char>::erase(__gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >, int)’
         csv_file_name.erase(csv_file_name.end()-8, 4);

好像只有一个参数。但是，如果我这样做：

csv_file_name = "loololololool.bag.csv";
csv_file_name.erase(13, 4);
std::cout << csv_file_name << std::endl;

它似乎工作正常。另外当我执行

csv_file_name = "loololololool.bag.csv";
csv_file_name.erase(csv_file_name.end()-8);
std::cout << csv_file_name << std::endl;

它按原样删除了单个字符。这怎么会发生？ csv_file_name.end()-8 必须有效，因为它会删除单个字符。采取两个论点也应该有效。但是组合没有？请帮忙！

Answer 1

您混淆了迭代器和索引。

string.erase(iter) //删除迭代器指向的字符
string.erase(iter1, iter2) // 删除两个迭代器之间的字符
string.erase(index, count) // 删除从 index

csv_file_name.end()-8 是一个迭代器，erase 没有采用迭代器和索引或计数的版本。

而不是

csv_file_name.erase(csv_file_name.end()-8, 4);

我想你的意思是

csv_file_name.erase(csv_file_name.size()-8, 4);

但实际上您应该能够阅读文档并自己解决这些问题。这样你会更有效率。

Answer 2

您混淆了 std::string::erase 的签名。有适用于一个或两个整数位置的重载，以及适用于一个或两个迭代器的另一组重载，请参阅 here.

您要做的是使用签名（迭代器、整数）调用擦除。这种重载根本不存在。

编辑太晚了:)

Answer 3

#include <bits/stdc++.h>
using namespace std; 
/*
  I have used this for this demonstration. However, it is
  not recommended to write this in larger projects. Please refer this  
*/
int main() {
    //I have taken the position of the first dot. This is the position
    //from where I am deleting 4 characters including the first dot.
    //This holds true given the structure of the string is as below.
    //Please note that as long as the string follows this structure
    //<any number of characters>.bag<any number of characters> this will pass.
    string s1 = "loololololool.bag.csv";
    string s2 = "loololololool.bag.csv";

    cout << "Demo 1 Analysis \n";
    //Please consult this link http://www.cplusplus.com/reference/string/string/erase/
    //Demo signature #1 string& erase (size_t pos = 0, size_t len = npos);-------
    int posFirstDot1 = s1.find('.');
    string result1 = s1.erase(posFirstDot1, 4);
    cout << s1 << endl;
    cout << "Address of result1 : " << &result1 << " and address of s1 : " << &s1 << endl;
    //Note that result1 and s1 are same but are present at different addresses. Thats Subtle :)
    //----------------------------------

    cout << "Demo 2 Analysis\n";
    //Demo signature #3 iterator  erase (const_iterator first, const_iterator last);
    int posFirstDot2 = s2.find('.');
    //get an iterator with s.begin() and posFirstDot3
    auto itFirstDot2 = next(s2.begin(), posFirstDot2);
    //we want to delete the next 4 characters starting from position of first dot
    auto itLastCharacterToBeRemoved = next(itFirstDot2, 4);
    auto result3 = s2.erase(itFirstDot2, itLastCharacterToBeRemoved);
    cout << s2 << endl;
    return 0;
}

string.erase 函数在特定情况下不起作用

string.erase function is not working in a specific case

c++

string

erase