1#include <iostream>
2#include <iomanip>
3#include <sstream>
4#include <nlohmann/json.hpp>
5
6using json = nlohmann::json;
7
8// a simple event consumer that collects string representations of the passed
9// values; note inheriting from json::json_sax_t is not required, but can
10// help not to forget a required function
11class sax_event_consumer : public json::json_sax_t
12{
13  public:
14    std::vector<std::string> events;
15
16    bool null() override
17    {
18        events.push_back("null()");
19        return true;
20    }
21
22    bool boolean(bool val) override
23    {
24        events.push_back("boolean(val=" + std::string(val ? "true" : "false") + ")");
25        return true;
26    }
27
28    bool number_integer(number_integer_t val) override
29    {
30        events.push_back("number_integer(val=" + std::to_string(val) + ")");
31        return true;
32    }
33
34    bool number_unsigned(number_unsigned_t val) override
35    {
36        events.push_back("number_unsigned(val=" + std::to_string(val) + ")");
37        return true;
38    }
39
40    bool number_float(number_float_t val, const string_t& s) override
41    {
42        events.push_back("number_float(val=" + std::to_string(val) + ", s=" + s + ")");
43        return true;
44    }
45
46    bool string(string_t& val) override
47    {
48        events.push_back("string(val=" + val + ")");
49        return true;
50    }
51
52    bool start_object(std::size_t elements) override
53    {
54        events.push_back("start_object(elements=" + std::to_string(elements) + ")");
55        return true;
56    }
57
58    bool end_object() override
59    {
60        events.push_back("end_object()");
61        return true;
62    }
63
64    bool start_array(std::size_t elements) override
65    {
66        events.push_back("start_array(elements=" + std::to_string(elements) + ")");
67        return true;
68    }
69
70    bool end_array() override
71    {
72        events.push_back("end_array()");
73        return true;
74    }
75
76    bool key(string_t& val) override
77    {
78        events.push_back("key(val=" + val + ")");
79        return true;
80    }
81
82    bool binary(json::binary_t& val) override
83    {
84        events.push_back("binary(val=[...])");
85        return true;
86    }
87
88    bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
89    {
90        events.push_back("parse_error(position=" + std::to_string(position) + ", last_token=" + last_token + ",\n            ex=" + std::string(ex.what()) + ")");
91        return false;
92    }
93};
94
95int main()
96{
97    // a JSON text
98    auto text = R"(
99    {
100        "Image": {
101            "Width":  800,
102            "Height": 600,
103            "Title":  "View from 15th Floor",
104            "Thumbnail": {
105                "Url":    "http://www.example.com/image/481989943",
106                "Height": 125,
107                "Width":  100
108            },
109            "Animated" : false,
110            "IDs": [116, 943, 234, -38793],
111            "DeletionDate": null,
112            "Distance": 12.723374634
113        }
114    }]
115    )";
116
117    // create a SAX event consumer object
118    sax_event_consumer sec;
119
120    // parse JSON
121    bool result = json::sax_parse(text, &sec);
122
123    // output the recorded events
124    for (auto& event : sec.events)
125    {
126        std::cout << event << "\n";
127    }
128
129    // output the result of sax_parse
130    std::cout << "\nresult: " << std::boolalpha << result << std::endl;
131}
132