c++ - 使用 Boost 解析后在 JSON 文件中查找重复项

Question

像下面的代码那样解析后，如何在 JSON 文件中找到重复项？我想计算数据中的重复项数，其中重复项的名字、姓氏和电子邮件地址都匹配。

JSON 文件比较大，这里就不复制粘贴了。但这是它的一个片段:

[  
  {  
    "firstName":"Cletus",
    "lastName":"Defosses",
    "emailAddress":"ea4ad81f-4111-4d8d-8738-ecf857bba992.Defosses@somedomain.org"
  },
  {  
    "firstName":"Sherron",
    "lastName":"Siverd",
    "emailAddress":"51c985c5-381d-4d0e-b5ee-83005f39ce17.Siverd@somedomain.org"
  },
  {  
    "firstName":"Garry",
    "lastName":"Eirls",
    "emailAddress":"cc43c2da-d12c-467f-9318-beb3379f6509.Eirls@somedomain.org"
  }]

这是 main.cpp 文件:

#include <iostream>
#include <string>

#include "Customer.h"
#include "boost\property_tree\ptree.hpp"
#include "boost\property_tree\json_parser.hpp"
#include "boost\foreach.hpp"

using namespace std;

int main()
{
    int numOfCustomers;

    // parse the JSON file
    boost::property_tree::ptree file;
    boost::property_tree::read_json("customers.json", file);

    cout << "Reading file..." << endl;

    numOfCustomers = file.size();

    // iterate over each top level entry
    BOOST_FOREACH(boost::property_tree::ptree::value_type const& rowPair, file.get_child(""))
    {
        // rowPair.first == ""  and rowPair.second is the subtree with names and emails

        // iterate over rows and columns
        BOOST_FOREACH(boost::property_tree::ptree::value_type const& itemPair, rowPair.second)
        {
            // e.g. itemPair.first == "firstName: " or "lastName: "
            cout << itemPair.first << ": ";
            // e.g. itemPair.second is the actual names and emails
            cout << itemPair.second.get_value<std::string>() << endl;
        }
        cout << endl;
    }
    cout << endl;

    return 0;
}

Customer 类只是一个通用类。

class Customer
{
private:
    std::string m_firstNme;
    std::string m_lastName;
    std::string m_emailAddress;

public:
    std::string getFirstName();
    void setFirstName(std::string firstName);

    std::string getLastName();
    void setLastName(std::string lastName);

    std::string getEmailAddress();
    void setEmailAddress(std::string emailAddress);
};

Answer 1

您通常会将客户对象/键插入到 std::set 中或 std::map并定义一个总排序，在插入时发现重复项。

定义关键函数和比较对象:

boost::tuple<string const&, string const&, string const&> key_of(Customer const& c) {
    return boost::tie(c.getFirstName(), c.getLastName(), c.getEmailAddress());
}

struct by_key {
    bool operator()(Customer const& a, Customer const& b) const {
        return key_of(a) < key_of(b);
    }
};

现在您可以简单地将对象插入 set<Customer, by_key> 中:

set<Customer, by_key> unique;

// iterate over each top level array
BOOST_FOREACH(boost::property_tree::ptree::value_type const& rowPair, file.get_child(""))
{
    Customer current;
    current.setFirstName    ( rowPair.second.get ( "firstName", "?"    )  ) ;
    current.setLastName     ( rowPair.second.get ( "lastName", "?"     )  ) ;
    current.setEmailAddress ( rowPair.second.get ( "emailAddress", "?" )  ) ;

    if (unique.insert(current).second)
        cout << current << "\n";
    else
        cout << "(duplicate skipped)\n";
}

完整演示

我在您的示例 JSON 中复制了 1 个条目，您可以实时查看它

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#include <iostream>
#include <string>
#include <set>

#include "Customer.h"
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/foreach.hpp>
#include <boost/tuple/tuple_comparison.hpp>

using namespace std;

namespace {

    boost::tuple<string const&, string const&, string const&> key_of(Customer const& c) {
        return boost::tie(c.getFirstName(), c.getLastName(), c.getEmailAddress());
    }

    struct by_key {
        bool operator()(Customer const& a, Customer const& b) const {
            return key_of(a) < key_of(b);
        }
    };

    inline ostream& operator<<(ostream& os, Customer const& c) {
        return os << "{ '"
             << c.getFirstName()    << "', '"
             << c.getLastName()     << "', '"
             << c.getEmailAddress() << " }";
    }
}

int main()
{
    // parse the JSON file
    boost::property_tree::ptree file;
    boost::property_tree::read_json("customers.json", file);

    cout << "Reading file..." << endl;

    set<Customer, by_key> unique;

    // iterate over each top level array
    BOOST_FOREACH(boost::property_tree::ptree::value_type const& rowPair, file.get_child(""))
    {
        Customer current;
        current.setFirstName    ( rowPair.second.get ( "firstName", "?"    )  ) ;
        current.setLastName     ( rowPair.second.get ( "lastName", "?"     )  ) ;
        current.setEmailAddress ( rowPair.second.get ( "emailAddress", "?" )  ) ;

        if (unique.insert(current).second)
            cout << current << "\n";
        else
            cout << "(duplicate skipped)\n";
    }

    cout << "\n" << (file.size() - unique.size()) << " duplicates were found\n";
}

打印:

Reading file...
{ 'Sherron', 'Siverd', '51c985c5-381d-4d0e-b5ee-83005f39ce17.Siverd@somedomain.org }
{ 'Cletus', 'Defosses', 'ea4ad81f-4111-4d8d-8738-ecf857bba992.Defosses@somedomain.org }
(duplicate skipped)
{ 'Garry', 'Eirls', 'cc43c2da-d12c-467f-9318-beb3379f6509.Eirls@somedomain.org }

1 duplicates were found

NOTE I've adjusted the getters to be less wasteful by returning const&:

std::string const& getFirstName() const        { return m_firstName;            } 
std::string const& getLastName() const         { return m_lastName;             } 
std::string const& getEmailAddress() const     { return m_emailAddress;         }

奖金

这是 26 行 c++14 代码的等效程序:

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