JSON for Modern C++  3.6.1

◆ 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>
basic_json nlohmann::basic_json::patch ( const basic_json json_patch) const
inline

JSON Patch defines a JSON document structure for expressing a sequence of operations to apply to a JSON) document. With this function, a JSON Patch is applied to the current JSON value by executing all operations from the patch.

Parameters
[in]json_patchJSON patch document
Returns
patched document
Note
The application of a patch is atomic: Either all operations succeed and the patched document is returned or an exception is thrown. In any case, the original value is not changed: the patch is applied to a copy of the value.
Exceptions
parse_error.104if the JSON patch does not consist of an array of objects
parse_error.105if the JSON patch is malformed (e.g., mandatory attributes are missing); example: "operation add must have member path"
out_of_range.401if an array index is out of range.
out_of_range.403if a JSON pointer inside the patch could not be resolved successfully in the current JSON value; example: "key baz not found"
out_of_range.405if JSON pointer has no parent ("add", "remove", "move")
other_error.501if "test" operation was unsuccessful
Complexity
Linear in the size of the JSON value and the length of the JSON patch. As usually only a fraction of the JSON value is affected by the patch, the complexity can usually be neglected.
Example
The following code shows how a JSON patch is applied to a value.
1 #include <iostream>
2 #include <iomanip>
3 #include <nlohmann/json.hpp>
4 
5 using json = nlohmann::json;
6 
7 int main()
8 {
9  // the original document
10  json doc = R"(
11  {
12  "baz": "qux",
13  "foo": "bar"
14  }
15  )"_json;
16 
17  // the patch
18  json patch = R"(
19  [
20  { "op": "replace", "path": "/baz", "value": "boo" },
21  { "op": "add", "path": "/hello", "value": ["world"] },
22  { "op": "remove", "path": "/foo"}
23  ]
24  )"_json;
25 
26  // apply the patch
27  json patched_doc = doc.patch(patch);
28 
29  // output original and patched document
30  std::cout << std::setw(4) << doc << "\n\n"
31  << std::setw(4) << patched_doc << std::endl;
32 }
basic_json<> json
default JSON class
Definition: json.hpp:871
basic_json patch(const basic_json &json_patch) const
applies a JSON patch
Definition: json.hpp:20231

Output (play with this example online):
{
    "baz": "qux",
    "foo": "bar"
}

{
    "baz": "boo",
    "hello": [
        "world"
    ]
}
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/patch.cpp -o patch 
See also
diff – create a JSON patch by comparing two JSON values
RFC 6902 (JSON Patch)
RFC 6901 (JSON Pointer)
Since
version 2.0.0

Definition at line 20231 of file json.hpp.