std::string at() method
- od C++20
- do C++20
// Non const version
constexpr reference at( size_type pos );
// Const version
constexpr const_reference at( size_type pos ) const;
// Non const version
reference at( size_type pos );
// Const version
const_reference at( size_type pos ) const;
Returns a reference
to the character at specified indexpos
.
Bounds checking is performed.
Parameters
pos
- position of the character to return
Return value
Reference to the requested character.
Exceptions
Throws std::out_of_range
if pos >= size()
.
Complexity
Constant - O(1).
Example
#include <stdexcept>
#include <iostream>
#include <string>
int main()
{
std::string s("message"); // for capacity
s = "abc";
s.at(2) = 'x'; // ok
std::cout << s << '\n';
std::cout << "string size = " << s.size() << '\n';
std::cout << "string capacity = " << s.capacity() << '\n';
try {
// This will throw since the requested offset is greater than the current size.
s.at(3) = 'x';
}
catch (std::out_of_range const& exc) {
std::cout << exc.what() << '\n';
}
}
Possible output
abx
string size = 3
string capacity = 7
basic_string::at
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