cpp-json/test/json_binder_custom_test.cxx

//
//  json_binder_custom.t.h
//  json
//
//  Created by Sam Jaffe on 9/12/17.
//

#include "json/json_binder.hpp"
#include <gmock/gmock.h>

#include <cmath>
#include <iomanip>

using namespace json::binder;
using namespace json::parser;

class precision_binder : public binder_impl<double> {
public:
  precision_binder(int d) : digits(d), trunc(std::pow(10, d)) {}
  virtual ~precision_binder() = default;

  binder_impl<double> * clone() const override {
    return new precision_binder{*this};
  }

  void parse(double & value, char const *& str, options) const override {
    std::sscanf(str, "%lf", &value);
    value = static_cast<long long>(value * trunc) / trunc;
    json::parse_discard_token(str); // Advance to the boundary
  }

  void write(double const & value, std::ostream & out) const override {
    out << std::fixed << std::setprecision(digits) << value;
  }

private:
  int digits;
  double trunc;
};

struct CustomObject {
  double A; // four_digits
  double B; // two_digits
  double C;
};

bool operator==(CustomObject const & lhs, CustomObject const & rhs) {
  return lhs.A == rhs.A && lhs.B == rhs.B && lhs.C == rhs.C;
}

class JsonBinderCustomTest : public ::testing::Test {
protected:
  static object_binder<CustomObject> & GetBinder() {
    static object_binder<CustomObject> val = object_binder<CustomObject>()(
        "A", &CustomObject::A, precision_binder(4))(
        "B", &CustomObject::B, precision_binder(2))("C", &CustomObject::C);
    return val;
  }
};

TEST_F(JsonBinderCustomTest, CustomBindersWillParse) {
  char data[] = "{\"A\":1.00008, \"B\":1.0, \"C\":1.523211102}";
  CustomObject out{0.0, 0.0, 0.0};
  CustomObject const expected{1.0, 1.0, 1.523211102};
  EXPECT_NO_THROW(parse(json::binder::bind(out, GetBinder()), data));
  EXPECT_THAT(out, expected);
}