In C++20, std::string and std::string_view gain new member functions starts_with and ends_with
that compare their argument to the prefix and postfix of the string.
These two functions introduce a standard, concise, and efficient way of checking the prefix and postfix for strings. The ad-hoc implementations
predating C++20 are often less readable, less efficient, and less reliable.
This rule raises an issue when an ad-hoc implementation checks prefixes or postfixes of a string.
Noncompliant code example
if (6 <= str.size() && str.substr(0, 6) == "prefix") { // Noncompliant
std::cout <<str <<" starts with the prefix\n";
}
if (6 <= str.size() && std::string_view(str.begin(), str.begin() + 6) == "prefix") { // Noncompliant
std::cout <<str <<" starts with the prefix\n";
}
if (7 <= str.size() && str.substr(str.size() - 7) == "postfix") { // Noncompliant
std::cout <<str <<" ends with the postfix\n";
}
Compliant solution
if (str.starts_with("prefix")) {
std::cout <<str <<" starts with the prefix\n";
}
if (str.ends_with("postfix")) {
std::cout <<str <<" ends with the postfix\n";
}
