nlohmann::operator<<(basic_json), nlohmann::operator<<(json_pointer)¶

std::ostream&operator<<(std::ostream&o,constbasic_json&j);// (1)
std::ostream&operator<<(std::ostream&o,constjson_pointer&ptr);// (2)

1. Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function.
   • The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
   • The indentation character can be controlled with the member variable fill of the output stream o. For instance, the manipulator std::setfill('\\t') sets indentation to use a tab character rather than the default space character.
2. Write a string representation of the given JSON pointer ptr to the output stream o. The string representation is obtained using the to_string member function.

Parameters¶

o (in, out)

stream to write to

j (in)

JSON value to serialize

ptr (in)

JSON pointer to write

Return value¶

the stream o

Exceptions¶

1. Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded. Note that unlike the dump member functions, no error_handler can be set.
2. None.

Complexity¶

Linear.

Notes¶

Examples¶

#include<iostream>
#include<iomanip>
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
intmain()
{
// create JSON values
jsonj_object={{"one",1},{"two",2}};
jsonj_array={1,2,4,8,16};
// serialize without indentation
std::cout<<j_object<<"\n\n";
std::cout<<j_array<<"\n\n";
// serialize with indentation
std::cout<<std::setw(4)<<j_object<<"\n\n";
std::cout<<std::setw(2)<<j_array<<"\n\n";
std::cout<<std::setw(1)<<std::setfill('\t')<<j_object<<"\n\n";
}

{"one":1,"two":2}
[1,2,4,8,16]
{
"one":1,
"two":2
}
[
1,
2,
4,
8,
16
]
{
"one":1,
"two":2
}

#include<iostream>
#include<nlohmann/json.hpp>
usingjson=nlohmann::json;
intmain()
{
// create JSON pointer
json::json_pointerptr("/foo/bar/baz");
// write string representation to stream
std::cout<<ptr<<std::endl;
}

/foo/bar/baz

Version history¶

1. Added in version 1.0.0. Added support for indentation character and deprecated std::ostream&operator>>(constbasic_json&j,std::ostream&o) in version 3.0.0.
2. Added in version 3.11.0.