Niels Lohmann
9856da2561
- API pages for get, get_to, get_string, number_token, and value of basic_json_view; JSON pointer overloads of operator[], at, and contains; links both ways with the basic_json pages - the feature page describes which conversions copy nothing - the examples show when the view helps: strings without copies, numbers exactly as written, and paths into a large text Signed-off-by: Niels Lohmann <mail@nlohmann.me>
30 lines
1.2 KiB
C++
30 lines
1.2 KiB
C++
#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using json_view = nlohmann::json_view;
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int main()
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{
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// a price and an order id from an incoming order -- both need to be
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// reproduced exactly, e.g. for an invoice or an audit log
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json_document doc = json_document::parse(R"(
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{"price": 19.90, "order_id": 1234567890123456789012345, "quantity": 3}
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)");
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const json_view order = doc.root();
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// number_token() returns the number exactly as written in the source
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std::cout << order["price"].number_token() << '\n';
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std::cout << order["order_id"].number_token() << '\n';
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// get<double>() converts it instead -- the exact source text is gone:
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// "19.90" becomes the double closest to 19.9, printed without the
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// trailing zero, and the 25-digit order id -- far beyond any 64-bit
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// integer -- can only be approximated as a double
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std::cout << order["price"].get<double>() << '\n';
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std::cout << order.materialize()["order_id"].dump() << '\n';
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// an ordinary quantity has nothing to lose either way
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std::cout << order["quantity"].number_token() << " == " << order["quantity"].get<int>() << '\n';
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}
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