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◆ get() [3/6]
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<typename ValueTypeCV , typename ValueType = detail::uncvref_t<ValueTypeCV>, detail::enable_if_t< not detail::is_basic_json< ValueType >::value and detail::has_from_json< basic_json_t, ValueType >::value and not detail::has_non_default_from_json< basic_json_t, ValueType >::value, int > = 0>
Explicit type conversion between the JSON value and a compatible value which is CopyConstructible and DefaultConstructible. The value is converted by calling the json_serializer<ValueType> from_json() method.
The function is equivalent to executing ValueType ret; JSONSerializer<ValueType>::from_json(*this, ret); return ret; This overloads is chosen if:
- Template Parameters
-
ValueTypeCV | the provided value type |
ValueType | the returned value type |
- Returns
- copy of the JSON value, converted to ValueType
- Exceptions
-
- Example^^ The example below shows several conversions from JSON values
- to other types. There a few things to note: (1) Floating-point numbers can be converted to integers, (2) A JSON array can be converted to a standard
std::vector<short> , (3) A JSON object can be converted to C++ associative containers such as std::unordered_map<std::string, json> . ^^ 2 #include <unordered_map> 3 #include <nlohmann/json.hpp> 16 { "floating-point", 17.23} 19 { "string", "Hello, world!"}, 20 { "array", {1, 2, 3, 4, 5}}, 25 auto v1 = json_types[ "boolean"].get< bool>(); 26 auto v2 = json_types[ "number"][ "integer"].get< int>(); 27 auto v3 = json_types[ "number"][ "integer"].get< short>(); 28 auto v4 = json_types[ "number"][ "floating-point"].get< float>(); 29 auto v5 = json_types[ "number"][ "floating-point"].get< int>(); 30 auto v6 = json_types[ "string"].get<std::string>(); 31 auto v7 = json_types[ "array"].get<std::vector<short>>(); 32 auto v8 = json_types.get<std::unordered_map<std::string, json>>(); 35 std::cout << v1 << '\n'; 36 std::cout << v2 << ' ' << v3 << '\n'; 37 std::cout << v4 << ' ' << v5 << '\n'; 38 std::cout << v6 << '\n'; 42 std::cout << i << ' '; 48 std::cout << i.first << ": " << i.second << '\n'; basic_json<> json default JSON class
Output (play with this example online):^^ 1
42 42
17.23 17
Hello, world!
1 2 3 4 5
string: "Hello, world!"
number: {"floating-point":17.23,"integer":42}
null: null
boolean: true
array: [1,2,3,4,5]
^^ The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/get__ValueType_const.cpp -o get__ValueType_const
- Since
- version 2.1.0
Definition at line 14961 of file json.hpp.
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