Skip to content

Latest commit

 

History

History
94 lines (70 loc) · 3.57 KB

decode_json.md

File metadata and controls

94 lines (70 loc) · 3.57 KB
Raw

jsoncons::decode_json

Decodes a JSON data format to a C++ data structure. decode_json will work for all C++ classes that have json_type_traits defined.

#include <jsoncons/decode_json.hpp>

template <class T, class Source>
T decode_json(const Source& s,
    const basic_json_decode_options<Source::value_type>& options 
        = basic_json_decode_options<Source::value_type>());                                     (1)

template <class T, class CharT>
T decode_json(std::basic_istream<CharT>& is,
    const basic_json_decode_options<CharT>& options = basic_json_decode_options<CharT>());      (2)

template <class T, class Iterator>
T decode_json(Iterator first, Iterator last,
    const basic_json_decode_options<CharT>& options = basic_json_decode_options<CharT>());      (3)

template <class T, class Source, class Allocator, class TempAllocator>
T decode_json(const allocator_set<Allocator,TempAllocator>& alloc_set,
    const Source& s,
    const basic_json_decode_options<Source::value_type>& options 
        = basic_json_decode_options<Source::value_type>());                                     (4) (since 0.171.0)

template <class T, class CharT, class Allocator, class TempAllocator>
T decode_json(const allocator_set<Allocator,TempAllocator>& alloc_set,
    std::basic_istream<CharT>& is,
    const basic_json_decode_options<CharT>& options = basic_json_decode_options<CharT>());      (5) (since 0.171.0)

(1) Reads JSON from a contiguous character sequence provided by s into a type T, using the specified (or defaulted) options. Type 'T' must be an instantiation of basic_json or support json_type_traits.

(2) Reads JSON from an input stream into a type T, using the specified (or defaulted) options. Type 'T' must be an instantiation of basic_json or support json_type_traits.

(3) Reads JSON from the range [first,last) into a type T, using the specified (or defaulted) options. Type 'T' must be an instantiation of basic_json or support json_type_traits.

Functions (1)-(3) perform encodings using the default json type basic_json<CharT>. Functions (4)-(5) are identical to (1)-(2) except an allocator_set is passed as an additional argument and provides allocators for result data and temporary allocations.

Exceptions

Throws a ser_error if parsing fails, and a conv_error if type conversion fails.Throws a ser_error if parsing fails, and a conv_error if type conversion fails, and a conv_error if type conversion fails.

Examples

Map with string-tuple pairs

#include <iostream>
#include <map>
#include <tuple>
#include <jsoncons/json.hpp>

int main()
{
    using employee_collection = std::map<std::string,std::tuple<std::string,std::string,double>>;

    std::string s = R"(
    {
        "Jane Doe": ["Commission","Sales",20000.0],
        "John Smith": ["Hourly","Software Engineer",10000.0]
    }
    )";

    employee_collection employees = jsoncons::decode_json<employee_collection>(s);

    for (const auto& pair : employees)
    {
        std::cout << pair.first << ": " << std::get<1>(pair.second) << std::endl;
    }
}

Output:

Jane Doe: Sales
John Smith: Software Engineer

See also

allocator_set

encode_json