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Niels Lohmann
d04f78864c
- API pages for set and push_back of basic_json_document and for the editable aliases; the class overviews name the Editable parameter - type_error.319 on the exceptions page - the feature page explains editing, and the examples show when it helps: a configuration file changed without reformatting it Signed-off-by: Niels Lohmann <mail@nlohmann.me>
42 lines
1.6 KiB
C++
42 lines
1.6 KiB
C++
#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json = nlohmann::json;
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using json_editable_document = nlohmann::json_editable_document;
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using json_editable_view = nlohmann::json_editable_view;
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int main()
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{
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// a configuration file, as it might be read from disk -- "price" is
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// written with a trailing zero that has no effect on its value
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const std::string text = R"({
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"name": "cache",
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"host": "db1",
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"port": 6379,
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"price": 19.90,
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"replicas": ["db2", "db3"],
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"timeout": 30
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})";
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json_editable_document doc = json_editable_document::parse(text);
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doc.set(doc.root()["port"], 6380); // (1) replace a value
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doc.set(doc.root(), "region", "us-east"); // (2) add a member
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doc.set(doc.root()["replicas"], 0, "db4"); // (3) assign an element
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doc.set(json::json_pointer("/timeout"), 45); // (4) via a JSON pointer
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// members stay in document order (the new one at the end), and a number
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// that was not itself edited keeps its exact spelling
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std::cout << doc.root().dump(2, ' ', false, json_editable_view::number_format::source) << "\n\n";
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// the same edits on a plain json value: object_t is a std::map, so
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// parsing already sorted the keys, and dump() rewrites every number to
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// its shortest form, even "price", which was never touched
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json plain = json::parse(text);
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plain["port"] = 6380;
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plain["region"] = "us-east";
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plain["replicas"][0] = "db4";
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plain[json::json_pointer("/timeout")] = 45;
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std::cout << plain.dump(2) << '\n';
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}
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