JSON for Modern C++ 2.1.1
Loading...
Searching...
No Matches

◆ front() [1/2]

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>
reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer >::front ( )
inline

Returns a reference to the first element in the container. For a JSON container c, the expression c.front() is equivalent to *c.begin().

Returns
In case of a structured type (array or object), a reference to the first element is returned. In case of number, string, or boolean values, a reference to the value is returned.
Complexity\n Constant.
Precondition
The JSON value must not be null (would throw std::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
Postcondition
The JSON value remains unchanged.
Exceptions
std::out_of_rangewhen called on null value
Example\n The following code shows an example for front(). \n @includelineno front.cpp \n Output (play with this example @htmlinclude front.link):\n @verbinclude front.output \n The example code above can be translated with @verbatim g++ -std=c++11 -Isrc doc/examples/front.cpp -o front @endverbatim
See also
back() – access the last element
Since
version 1.0.0

Definition at line 4192 of file json.hpp.