deque.at No Maching Function

December 14, 2021

I am trying to deque (a string element) from a deque data structure. But I am getting and error:

error: no matching function for call to ‘std::__cxx11::basic_string::basic_string(__gnu_cxx::__alloc_traitsstd::allocator<std::array<std::__cxx11::basic_string<char, 1> >, std::arraystd::__cxx11::basic_string<char, 1> >::value_type&)’
26 | string record = (string)records.at(0);

deque<array<string, 1>>     records;
string data("hello this is 1st record");
array<string, 1>        buffer{data};
records.push_back(buffer);

string record = (string)records.at(0); //error is reported at this line
printf("%s\n", record.c_str());

Can someone please give me a hint what I am doing wrongly.
As background, I have to cache the last 100 text messages, so I am using deque for this purpose.

>Solution :

It is not quite clear why you are using array as elements. The value returned from at is not a string but an array.

deque<array<string, 1>>     records;
string data("hello this is 1st record");
array<string, 1>        buffer{data};
records.push_back(buffer);

string record = records.at(0)[0];
                        ^^ get first element in deque
                              ^^ get first element in array

Do not use c-style casts ((string)...). They are almost always wrong (and when they are not, they should be replaced with a safer C++ cast). If you do not use the array (why? when it only holds a single element?) the code is

deque<string>     records;
string data("hello this is 1st record");
records.push_back(data);

string record = records.at(0);
                        ^^ get first element in deque