Using the low-level parser
The following code snippet shows how to use the low-level json_parser
class by providing an own handler class and passing it as a template argument:
#include <orcus/json_parser.hpp>
#include <cstring>
#include <iostream>
using namespace std;
class json_parser_handler : public orcus::json_handler
{
public:
void object_key(std::string_view key, bool /*transient*/)
{
cout << "object key: " << key << endl;
}
void string(std::string_view val, bool /*transient*/)
{
cout << "string: " << val << endl;
}
void number(double val)
{
cout << "number: " << val << endl;
}
};
int main()
{
const char* test_code = "{\"key1\": [1,2,3,4,5], \"key2\": 12.3}";
cout << "JSON string: " << test_code << endl;
// Instantiate the parser with an own handler.
json_parser_handler hdl;
orcus::json_parser<json_parser_handler> parser(test_code, hdl);
// Parse the string.
parser.parse();
return EXIT_SUCCESS;
}
The parser constructor expects the char array, its length, and the handler
instance. The base handler class json_handler
implements
all required handler methods. By inheriting from it, you only need to
implement the handler methods you need. In this example, we are only
implementing the object_key()
,
string()
, and number()
methods to process object key values, string values and numeric values,
respectively. Refer to the json_handler
class definition
for all available handler methods.
Executing this code will generate the following output:
JSON string: {"key1": [1,2,3,4,5], "key2": 12.3}
object key: key1
number: 1
number: 2
number: 3
number: 4
number: 5
object key: key2
number: 12.3