nlohmann::basic_json::merge_patch¶
voidmerge_patch(constbasic_json&apply_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 fromTarget
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¶
apply_patch(in)- the patch to apply
Complexity¶
Linear in the lengths of apply_patch.
Examples¶
Example
The following code shows how a JSON Merge Patch is applied to a JSON document.
#include<iostream>
#include<nlohmann/json.hpp>
#include<iomanip> // for std::setw
usingjson=nlohmann::json;
usingnamespacenlohmann::literals;
intmain()
{
// the original document
jsondocument=R"({
"title": "Goodbye!",
"author": {
"givenName": "John",
"familyName": "Doe"
},
"tags": [
"example",
"sample"
],
"content": "This will be unchanged"
})"_json;
// the patch
jsonpatch=R"({
"title": "Hello!",
"phoneNumber": "+01-123-456-7890",
"author": {
"familyName": null
},
"tags": [
"example"
]
})"_json;
// apply the patch
document.merge_patch(patch);
// output original and patched document
std::cout<<std::setw(4)<<document<<std::endl;
}
Output:
{
"author":{
"givenName":"John"
},
"content":"This will be unchanged",
"phoneNumber":"+01-123-456-7890",
"tags":[
"example"
],
"title":"Hello!"
}
See also¶
- RFC 7396 (JSON Merge Patch)
- patch apply a JSON patch
Version history¶
- Added in version 3.0.0.