如何从字符串中提取多个子字符串？

Question

My original string looks like this <Information name="Identify" id="IdentifyButton" type="button"/>

from this string, how do extract 3 substrings string name_part = Identify , string id_part="IdentifyButton" , type_part="button"

Answer 1

Assuming you don't want to use third-party XML parsers, you can simply use std::string 's find() for each of your names:

int main()
{
  std::string s("<Information name = \"Identify\" id = \"IdentifyButton\" type = \"button\" / >");
  std::string names[] = { "name = \"" , "id = \"" , "type = \"" };
  std::string::size_type posStart(0), posEnd(0);
  for (auto& n : names)
  {
    posStart = s.find(n, posEnd) + n.length();
    posEnd = s.find("\"", posStart);
    std::string part = s.substr(posStart, posEnd - posStart);
    std::cout << part << std::endl;
    posEnd++;
  }
}

Add error checking per your tolerance:)

Answer 2

You could use a regex to extract key-value pairs separated by a '=' with optional space characters in between:

(\S+?)\s*=\s*([^ />]+)

[^ />]+ captures a value consisting of characters other than space, / and >. This will capture values with or without quotes.

Then use std::regex_iterator , a read-only forward iterator, that will call std::regex_search() with the regex. Here's an example:

#include <string>
#include <regex>
#include <iostream>

using namespace std::string_literals;

int main()
{
    std::string mystring = R"(<Information name="Identify" id="IdentifyButton" type="button" id=1/>)"s;
    std::regex reg(R"((\S+?)\s*=\s*([^ />]+))");
    auto start = std::sregex_iterator(mystring.begin(), mystring.end(), reg);
    auto end = std::sregex_iterator{};

    for (std::sregex_iterator it = start; it != end; ++it)
    {
        std::smatch mat = *it;
        auto key = mat[1].str();
        auto value = mat[2].str();
        std::cout << key << "_part=" << value << std::endl;
    }
}

Output:

name_part="Identify"
id_part="IdentifyButton"
type_part="button"
id_part=1

Here's a Demo . Requires at least C++11.