Class usage primer.md

A simple example of class usage and its interface (c++14):

Say, we want to write a simple programm in c++ achieveing a following task:

1. read Address Book JSON from <stdin>
2. sort all records by Name (for simplicity, assume all records have that label)
3. output resulting Address Book JSON

Below is the code sample how that could be achieved using Json.hpp class and the source JSON - Address Book:

#include <iostream>
#include <fstream>
#include "lib/Json.hpp"

// compile with: c++ -o sort_ab -Wall -std=c++14 sorting_ab.cpp
using namespace std;


int main(int argc, char *argv[]) { 
 // read and parse json from cin:
 Json jin{ {istream_iterator<char>{cin>>noskipws}, istream_iterator<char>{}} };
 
 // get all the names into vector and sort them
 vector<string> names{jin.walk("<Name>l:"), jin.walk().end()};
 sort(names.begin(), names.end());

 // rebuild AB with sorted records:
 Json sorted = ARY{};
 for(const auto &name: names)
  sorted.push_back(move( *jin.walk("[Name]:<" + name + ">[-1]") ));

 // // put back into the original container and print using indentation 3 
 jin["AddressBook"].clear().push_back( move(sorted) ); 
 cout << jin.tab(3) << endl;
}

Output result:

bash $ c++ -o sort_ab -Wall -std=c++14 sorting_ab.cpp
bash $ 
bash $ <addressbook-sample.json sort_ab | jtc -tc      # using jtc here only for a compact view
{
   "AddressBook": [
      [
         {
            "Name": "Ivan",
            "address": { "city": "Seattle", "postal code": 98104, "state": "WA", "street address": "5423 Madison St" },
            "age": 31,
            "children": [],
            "phoneNumbers": [
               { "number": "573 923-6483", "type": "home" },
               { "number": "523 283-0372", "type": "mobile" }
            ],
            "spouse": null
         },
         {
            "Name": "Jane",
            "address": { "city": "Denver", "postal code": 80206, "state": "CO", "street address": "6213 E Colfax Ave" },
            "age": 25,
            "children": [ "Robert", "Lila" ],
            "phoneNumbers": [
               { "number": "358 303-0373", "type": "office" },
               { "number": "333 638-0238", "type": "home" }
            ],
            "spouse": "Chuck"
         },
         {
            "Name": "John",
            "address": { "city": "New York", "postal code": 10012, "state": "NY", "street address": "599 Lafayette St" },
            "age": 25,
            "children": [ "Olivia" ],
            "phoneNumbers": [
               { "number": "212 555-1234", "type": "mobile" },
               { "number": "213 123-2368", "type": "mobile" }
            ],
            "spouse": "Martha"
         }
      ]
   ]
}
bash $ 

for the complete description of Json class interface, refer to Json.hpp

Btw, the same sorting is achievable using <>g lexeme in jtc walk:

bash $ <addressbook-sample.json jtc -tc -w'[0]' -pi'[Name]:<>g:[-1]'
{
   "AddressBook": [
      {
         "Name": "Ivan",
         "address": { "city": "Seattle", "postal code": 98104, "state": "WA", "street address": "5423 Madison St" },
         "age": 31,
         "children": [],
         "phoneNumbers": [
            { "number": "573 923-6483", "type": "home" },
            { "number": "523 283-0372", "type": "mobile" }
         ],
         "spouse": null
      },
      {
         "Name": "Jane",
         "address": { "city": "Denver", "postal code": 80206, "state": "CO", "street address": "6213 E Colfax Ave" },
         "age": 25,
         "children": [ "Robert", "Lila" ],
         "phoneNumbers": [
            { "number": "358 303-0373", "type": "office" },
            { "number": "333 638-0238", "type": "home" }
         ],
         "spouse": "Chuck"
      },
      {
         "Name": "John",
         "address": { "city": "New York", "postal code": 10012, "state": "NY", "street address": "599 Lafayette St" },
         "age": 25,
         "children": [ "Olivia" ],
         "phoneNumbers": [
            { "number": "212 555-1234", "type": "mobile" },
            { "number": "213 123-2368", "type": "mobile" }
         ],
         "spouse": "Martha"
      }
   ]
}
bash $