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◆ unflatten()
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>
The function restores the arbitrary nesting of a JSON value that has been flattened before using the flatten() function. The JSON value must meet certain constraints:
- The value must be an object.
- The keys must be JSON pointers (see RFC 6901)
- The mapped values must be primitive JSON types.
- Returns
- the original JSON from a flattened version
- Note
- Empty objects and arrays are flattened by flatten() to
null values and can not unflattened to their original type. Apart from this example, for a JSON value j , the following is always true: j == j.flatten().unflatten() .
- Complexity^^ Linear in the size the JSON value.
- Exceptions
-
type_error.314 | if value is not an object |
type_error.315 | if object values are not primitive |
- Example^^ The following code shows how a flattened JSON object is
- unflattened into the original nested JSON object. ^^
3 #include <nlohmann/json.hpp> 12 { "/answer/everything", 42}, 18 { "/nothing", nullptr}, 19 { "/object/currency", "USD"}, 20 { "/object/value", 42.99}, 25 std::cout << std::setw(4) << j_flattened.unflatten() << '\n'; basic_json<> json default JSON class
Output (play with this example online):^^ {
"answer": {
"everything": 42
},
"happy": true,
"list": [
1,
0,
2
],
"name": "Niels",
"nothing": null,
"object": {
"currency": "USD",
"value": 42.99
},
"pi": 3.141
}
^^ The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/unflatten.cpp -o unflatten
- See also
- flatten() for the reverse function
- Since
- version 2.0.0
Definition at line 19737 of file json.hpp.
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