merge_patch()

template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer, class BinaryType = std::vector<std::uint8_t>>

void nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::merge_patch ( const basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType > &  apply_patch )

inline

applies a JSON Merge Patch

The merge patch format is primarily intended for use with the HTTP PATCH method as a means of describing a set of modifications to a target resource's content. This function applies a merge patch to the current JSON value.

The function implements the following algorithm from Section 2 of RFC 7396 (JSON Merge Patch):

define MergePatch(Target, Patch):
  if Patch is an Object:
    if Target is not an Object:
      Target = {} // Ignore the contents and set it to an empty Object
    for each Name/Value pair in Patch:
      if Value is null:
        if Name exists in Target:
          remove the Name/Value pair from Target
      else:
        Target[Name] = MergePatch(Target[Name], Value)
    return Target
  else:
    return Patch

Thereby, Target is the current object; that is, the patch is applied to the current value.

Parameters

[in]

apply_patch

the patch to apply

@complexity Linear in the lengths of patch.

@liveexample{The following code shows how a JSON Merge Patch is applied to a JSON document.,merge_patch}

See also

see patch – apply a JSON patch

RFC 7396 (JSON Merge Patch)

Since

version 3.0.0

Definition at line 26651 of file json.hpp.

    {
        if (apply_patch.is_object())
        {
            if (!is_object())
            {
                *this = object();
            }
 
            for (auto it = apply_patch.begin(); it != apply_patch.end(); ++it)
            {
                if (it.value().is_null())
                {
                    erase(it.key());
                }
 
                else
                {
                    operator[](it.key()).merge_patch(it.value());
                }
            }
        }
 
        else
        {
            *this = apply_patch;
        }
    }