Parsing key/value pairs from a string in C++

Question

I\'m working in C++11, no Boost. I have a function that takes as input a std::string that contains a series of key-value pairs, delimited with semicolons, and returns an object

Answer 1

Do you care about performance or readability? If readability is good enough, then pick your favorite version of split from this question and away we go:

std::map<std::string, std::string> tag_map;

for (const std::string& tag : split(input, ';')) {
    auto key_val = split(input, '=');
    tag_map.insert(std::make_pair(key_val[0], key_val[1]));
}


S s{std::stoi(tag_map["top"]),
    std::stoi(tag_map["bottom"]),
    tag_map["name"]};

Answer 2

For an easy readable solution, you can e.g. use std::regex_token_iterator and a sorted container to distinguish the attribute value pairs (alternatively use an unsorted container and std::sort).

std::regex r{R"([^;]+;)"};
std::set<std::string> tokens{std::sregex_token_iterator{std::begin(s), std::end(s), r}, std::sregex_token_iterator{}};

Now the attribute value strings are sorted lexicographically in the set tokens, i.e. the first is Bottom, then Name and last Top.

Lastly use a simple std::string::find and std::string::substr to extract the desired parts of the string.

Live example