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◆ emplace_back()
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, class BinaryType = std::vector<std::uint8_t>>
template<class... Args>
reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::emplace_back |
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Args &&... |
args | ) |
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Creates a JSON value from the passed parameters args to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending the value created from args.
- Parameters
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[in] | args | arguments to forward to a constructor of basic_json |
- Template Parameters
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Args | compatible types to create a basic_json object |
- Returns
- reference to the inserted element
- Exceptions
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type_error.311 | when called on a type other than JSON array or null; example: "cannot use emplace_back() with number" |
- Complexity
- Amortized constant.
- Example
- The example shows how
push_back() can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.
2#include <nlohmann/json.hpp>
9 json array = {1, 2, 3, 4, 5};
13 std::cout << array << '\n';
14 std::cout << null << '\n';
17 array.emplace_back(6);
18 null.emplace_back( "first");
19 null.emplace_back(3, "second");
22 std::cout << array << '\n';
23 std::cout << null << '\n';
basic_json<> json default JSON class
Output (play with this example online): [1,2,3,4,5]
null
[1,2,3,4,5,6]
["first",["second","second","second"]]
The example code above can be translated with g++ -std=c++11 -Isingle_include doc/examples/emplace_back.cpp -o emplace_back
- Since
- version 2.0.8, returns reference since 3.7.0
Definition at line 23155 of file json.hpp.
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