mirror of
https://github.com/nlohmann/json.git
synced 2026-10-12 20:05:23 +00:00
c6ee5a64be
basic_json_document gets a second template parameter, Editable (false by default), plus the aliases json_editable_document, json_editable_view, ordered_json_editable_document and ordered_json_editable_view. Editable documents can change values and structure without rewriting the source text: set()/push_back() on values, keys, array indices and JSON pointers; insert() before an array element; erase() of an object key, array index or JSON pointer. New values and element sequences go into edit storage that the document owns and never moves, so views keep referring to their value across edits and a parsed node never moves. Read-only documents walk the plain node array and are unaffected. Strings are checked for UTF-8 on entry, so dump() of an editable document never throws type_error.316. Binary values cannot be stored (type_error.319). A seeded differential test applies random edits to an editable document and to the equivalent ordered_json and compares both after every step. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
31 lines
1.1 KiB
C++
31 lines
1.1 KiB
C++
#include <iostream>
|
|
#include <nlohmann/json_view.hpp>
|
|
|
|
using json = nlohmann::json;
|
|
using json_editable_document = nlohmann::json_editable_document;
|
|
using json_editable_view = nlohmann::json_editable_view;
|
|
|
|
int main()
|
|
{
|
|
// a configuration file, as it might be read from disk
|
|
const std::string text = R"({"name": "cache", "host": "db1", "port": 6379, "price": 19.90})";
|
|
std::cout << text << "\n\n";
|
|
|
|
// patch two fields -- "price" is never touched
|
|
json_editable_document doc = json_editable_document::parse(text);
|
|
doc.set(doc.root(), "host", "db2");
|
|
doc.set(doc.root(), "retries", 3);
|
|
|
|
// member order (the new member at the end) and the untouched number's
|
|
// exact spelling survive
|
|
std::cout << doc.root().dump(-1, ' ', false, json_editable_view::number_format::source) << '\n';
|
|
|
|
// the same patch on a plain json value: keys are sorted (object_t is a
|
|
// std::map), and "price" is rewritten even though the patch never
|
|
// touched it
|
|
json plain = json::parse(text);
|
|
plain["host"] = "db2";
|
|
plain["retries"] = 3;
|
|
std::cout << plain.dump() << '\n';
|
|
}
|