iterator_wrapper() [2/2]

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>>

static iteration_proxy< iterator > nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer, BinaryType >::iterator_wrapper ( reference  ref )

inlinestaticnoexcept

wrapper to access iterator member functions in range-based for

This function allows to access iterator::key() and iterator::value() during range-based for loops. In these loops, a reference to the JSON values is returned, so there is no access to the underlying iterator.

For loop without iterator_wrapper:

for (auto it = j_object.begin(); it != j_object.end(); ++it)
{
    std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}

Range-based for loop without iterator proxy:

for (auto it : j_object)
{
    // "it" is of type json::reference and has no key() member
    std::cout << "value: " << it << '\n';
}

Range-based for loop with iterator proxy:

for (auto it : json::iterator_wrapper(j_object))
{
    std::cout << "key: " << it.key() << ", value:" << it.value() << '\n';
}

Note

When iterating over an array, key() will return the index of the element as string (see example).

Parameters

[in]

ref

reference to a JSON value

Returns

iteration proxy object wrapping ref with an interface to use in range-based for loops

@liveexample{The following code shows how the wrapper is used,iterator_wrapper}

@exceptionsafety Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

@complexity Constant.

Note

The name of this function is not yet final and may change in the future.

Deprecated:

This stream operator is deprecated and will be removed in future 4.0.0 of the library. Please use items() instead; that is, replace json::iterator_wrapper(j) with j.items().

Definition at line 22685 of file json.hpp.

    {
        return ref.items();
    }