std::basic_string<CharT,Traits,Allocator>::assign
Min standard notice:
Replaces the contents of the string.
# Declarations
basic_string& assign( const basic_string& str );
(constexpr since C++20)
basic_string& assign( basic_string&& str ) noexcept(/* see below */);
(since C++11) (constexpr since C++20)
basic_string& assign( size_type count, CharT ch );
(constexpr since C++20)
basic_string& assign( const CharT* s, size_type count );
(constexpr since C++20)
basic_string& assign( const CharT* s );
(constexpr since C++20)
template< class SV >
basic_string& assign( const SV& t );
(since C++17) (constexpr since C++20)
template< class SV >
basic_string& assign( const SV& t,
size_type pos, size_type count = npos);
(since C++17) (constexpr since C++20)
basic_string& assign( const basic_string& str,
size_type pos, size_type count );
(until C++14)
basic_string& assign( const basic_string& str,
size_type pos, size_type count = npos);
(since C++14) (constexpr since C++20)
template< class InputIt >
basic_string& assign( InputIt first, InputIt last );
(constexpr since C++20)
basic_string& assign( std::initializer_list<CharT> ilist );
(since C++11) (constexpr since C++20)
# Parameters
str: string to be used as source to initialize the characters withcount: size of the resulting stringch: value to initialize characters of the string withs: pointer to a character string to use as source to initialize the string witht: object (convertible to std::basic_string_view) to initialize the characters of the string withpos: index of the first character to takefirst, last: range to copy the characters fromilist: std::initializer_list to initialize the characters of the string with
# Return value
*this
# Example
#include <iostream>
#include <iterator>
#include <string>
int main()
{
std::string s;
// assign(size_type count, CharT ch)
s.assign(4, '=');
std::cout << s << '\n'; // "===="
std::string const c("Exemplary");
// assign(const basic_string& str)
s.assign(c);
std::cout << c << " == " << s << '\n'; // "Exemplary == Exemplary"
// assign(const basic_string& str, size_type pos, size_type count)
s.assign(c, 0, c.length() - 1);
std::cout << s << '\n'; // "Exemplar";
// assign(basic_string&& str)
s.assign(std::string("C++ by ") + "example");
std::cout << s << '\n'; // "C++ by example"
// assign(const CharT* s, size_type count)
s.assign("C-style string", 7);
std::cout << s << '\n'; // "C-style"
// assign(const CharT* s)
s.assign("C-style\0string");
std::cout << s << '\n'; // "C-style"
char mutable_c_str[] = "C-style string";
// assign(InputIt first, InputIt last)
s.assign(std::begin(mutable_c_str), std::end(mutable_c_str) - 1);
std::cout << s << '\n'; // "C-style string"
// assign(std::initializer_list<CharT> ilist)
s.assign({'C', '-', 's', 't', 'y', 'l', 'e'});
std::cout << s << '\n'; // "C-style"
}
# Defect reports
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 847 | C++98 | there was no exception safety guarantee | added strong exception safety guarantee |
| LWG 2063 | C++11 | non-normative note stated that overload (2)can be implemented by swapping | corrected to require move assignment |
| LWG 2250 | C++98 | the behavior of overload (8) wasundefined if pos > str.size() is true | always throws an exception in this case |
| LWG 2579 | C++98 | overload (1) and the copy assignmentoperator had different effects | they have the same effect |
| LWG 2946 | C++17 | overload (6) caused ambiguity in some cases | avoided by making it a template |