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>
template<class... Args>
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
-
[in] | args | arguments to forward to a constructor of basic_json |
- Template Parameters
-
Args | compatible types to create a basic_json object |
- Exceptions
-
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> 13 std::cout <<
array <<
'\n';
14 std::cout <<
null <<
'\n';
18 null.emplace_back(
"first");
19 null.emplace_back(3,
"second");
22 std::cout <<
array <<
'\n';
23 std::cout <<
null <<
'\n';
static basic_json array(initializer_list_t init={})
explicitly create an array from an initializer list
basic_json<> json
default JSON class
void emplace_back(Args &&... args)
add an object to an array
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 withg++ -std=c++11 -Isingle_include doc/examples/emplace_back.cpp -o emplace_back
- Since
- version 2.0.8
Definition at line 17756 of file json.hpp.