JSON for Modern C++ 3.0

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basic_json
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~basic_json
| 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 = int64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
using nlohmann::basic_json::object_t = ObjectType<StringType, basic_json, std::less<StringType>, AllocatorType<std::pair<const StringType, basic_json>>>
RFC 7159 describes JSON objects as follows: An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array. To store objects in C++, a type is defined by the template parameters ObjectType which chooses the container (e.g., `std::map` or `std::unordered_map`), StringType which chooses the type of the keys or names, and AllocatorType which chooses the allocator to use. #### Default type With the default values for ObjectType (`std::map`), StringType (`std::string`), and AllocatorType (`std::allocator`), the default value for object_t is: std::map< std::string, // key_type basic_json, // value_type std::less<std::string>, // key_compare std::allocator<std::pair<const std::string, basic_json>> // allocator_type > #### Behavior The choice of object_t influences the behavior of the JSON class. With the default type, objects have the following behavior: When all names are unique, objects will be interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings. When the names within an object are not unique, later stored name/value pairs overwrite previously stored name/value pairs, leaving the used names unique. For instance, `{"key": 1}` and `{"key": 2, "key": 1}` will be treated as equal and both stored as `{"key": 1}`. Internally, name/value pairs are stored in lexicographical order of the names. Objects will also be serialized (see dump) in this order. For instance, `{"b": 1, "a": 2}` and `{"a": 2, "b": 1}` will be stored and serialized as `{"a": 2, "b": 1}`. When comparing objects, the order of the name/value pairs is irrelevant. This makes objects interoperable in the sense that they will not be affected by these differences. For instance, `{"b": 1, "a": 2}` and `{"a": 2, "b": 1}` will be treated as equal. #### Limits RFC 7159 specifies: An implementation may set limits on the maximum depth of nesting. In this class, the object's limit of nesting is not constraint explicitly. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON object. #### Storage Objects are stored as pointers in a `basic_json` type. That is, for any access to object values, a pointer of type `object_t*` must be dereferenced. See also array_t