xentara::utils::json::decoder::Object Class Reference

An accessor used for reading the members of a JSON object. More...

#include <xentara/utils/json/decoder/Object.hpp>

Inheritance diagram for xentara::utils::json::decoder::Object:

Classes
class	Iterator
	An iterator to iterator to iterate over the members. More...
struct	Member
	A member of an object. More...

Public Member Functions
	Object ()=delete
	This type is not user-constructible.
internal auto	begin () -> Iterator
	Returns an object that can be used to iterate over the members.
constexpr auto	end () noexcept -> std::default_sentinel_t
	Returns an sentinel that can be used to determine if an iterator is exhausted.
auto	document () const -> std::reference_wrapper< const Document >
	Gets the JSON document that the object belongs to.
auto	lineNumber () const -> std::uint_least32_t
	Gets the line number in the JSON document that the object is on.
auto	location () const -> Location
	Gets the location of the object within the JSON document.
template<typename Filter > requires std::is_invocable_r_v<bool, std::decay_t<Filter>, const Name &, Value &>
auto	filter (Filter &&filter) &-> Object &
	Adds a filter to filter out selected members.
template<typename Filter > requires std::is_invocable_r_v<bool, std::decay_t<Filter>, const Name &, Value &>
auto	filter (Filter &&filter) &&-> Object &&
	Adds a filter to filter out selected members.

Detailed Description

An accessor used for reading the members of a JSON object.

Objects of this class can be moved, but not copied.

Constructor & Destructor Documentation

Object()

xentara::utils::json::decoder::Object::Object ( )

delete

This type is not user-constructible.

Member Function Documentation

begin()

auto xentara::utils::json::decoder::Object::begin

(

)

-> Iterator

Returns an object that can be used to iterate over the members.

Returns

An iterator that allows reading of the members

Exceptions

std::runtime_error

An error occured reading the first member from the stream

document()

auto xentara::utils::json::decoder::Object::document

(

)

const -> std::reference_wrapper<const Document>

Gets the JSON document that the object belongs to.

Returns

The document

end()

constexpr auto xentara::utils::json::decoder::Object::end ( ) -> std::default_sentinel_t

constexprnoexcept

Returns an sentinel that can be used to determine if an iterator is exhausted.

Returns

An sentinel for member iterators

filter() [1/2]

template<typename Filter >
requires std::is_invocable_r_v<bool, std::decay_t<Filter>, const Name &, Value &>

auto xentara::utils::json::decoder::Object::filter

(

Filter &&

filter

)

&& -> Object &&

Adds a filter to filter out selected members.

Filters can be used to filter out selected members when iterating over the object. The members can either be skipped entirely, or they can be read and handled by the filter function.

The filter is called with the name and value of each member of the object. The name and the type of the value can be examined to determine whether the member should be filtered out. If the member is filtered out, then the value must either be skipped using Value::skip(), or read using one of the read functions, like Value::asString(), Value::asNumber(), or Value::asObject(), or a conversion function like Value::toUuid() or Value::toDateTime(). The filter function can discard the value, or use it to perform some sort of processing.

If the member is filtered out, the filter function must return true. If the member is to be handled normally by the iterators, the filter function must return false. If the filter function returns false, the value of the object must not be read.

Here is an example of a filter function that skips all members named "$comment":

auto filterComments(const Name &name, Value &value) -> bool
{
    if (name == "$comment"sv)
    {
        value.skip();
        return true;    
    }
 
    return false;
}

Here is an example of a filter object that filters out the "$schema" member, and stores the schema URL in a variable:

class SchemaFilter final
{
public:
    auto operator()(const Name &name, Value &value) -> bool
    {
        if (name == "$schema"sv)
        {
            _schema = value.asString<std::string>();
            return true;    
        }
    
        return false;
    }
 
private:
    std::string _schema;
};

Parameters

filter

The filter to use to filter out the objects. The return value of the filter must be convertible to bool.

Returns

A reference to this object

filter() [2/2]

template<typename Filter >
requires std::is_invocable_r_v<bool, std::decay_t<Filter>, const Name &, Value &>

auto xentara::utils::json::decoder::Object::filter

(

Filter &&

filter

)

& -> Object &

Adds a filter to filter out selected members.

Filters can be used to filter out selected members when iterating over the object. The members can either be skipped entirely, or they can be read and handled by the filter function.

The filter is called with the name and value of each member of the object. The name and the type of the value can be examined to determine whether the member should be filtered out. If the member is filtered out, then the value must either be skipped using Value::skip(), or read using one of the read functions, like Value::asString(), Value::asNumber(), or Value::asObject(), or a conversion function like Value::toUuid() or Value::toDateTime(). The filter function can discard the value, or use it to perform some sort of processing.

If the member is filtered out, the filter function must return true. If the member is to be handled normally by the iterators, the filter function must return false. If the filter function returns false, the value of the object must not be read.

Here is an example of a filter function that skips all members named "$comment":

auto filterComments(const Name &name, Value &value) -> bool
{
    if (name == "$comment"sv)
    {
        value.skip();
        return true;    
    }
 
    return false;
}

Here is an example of a filter object that filters out the "$schema" member, and stores the schema URL in a variable:

class SchemaFilter final
{
public:
    auto operator()(const Name &name, Value &value) -> bool
    {
        if (name == "$schema"sv)
        {
            _schema = value.asString<std::string>();
            return true;    
        }
    
        return false;
    }
 
private:
    std::string _schema;
};

Parameters

filter

The filter to use to filter out the objects. The return value of the filter must be convertible to bool.

Returns

A reference to this object

lineNumber()

auto xentara::utils::json::decoder::Object::lineNumber

(

)

const -> std::uint_least32_t

Gets the line number in the JSON document that the object is on.

Returns

The line number of the curly brace that opens the object

location()

auto xentara::utils::json::decoder::Object::location

(

)

const -> Location

Gets the location of the object within the JSON document.

Returns

The location of the curly brace that opens the object