[BUG]: Getters for optional values in C++ should return a const reference

[flounderpinto]

Currently, the get_xyz() methods return a copy of optional values. Something like:
boost::optional<std::vector<Coordinate>> get_coordinates() const { return coordinates; }
Which makes this code not behave as expected:
for (auto coordinate: test.get_coordinates()) std::cout << "latitude" << coordinate.get_latitude() << std::endl;
Required getters work as expected:
'const std::vector & get_coordinates_required() const { return coordinates_required; }'

Issue Type

This is an issue with quicktype C++ code generation.

Context (Environment, Version, Language)

Input Format: Json Scheam
Output Language: C++

CLI, npm, or app.quicktype.io:
Version: Current

Description

Returning a copy of the boost::optional means that user's can't iterate through the vector as they might initially expect, leading to bugs. It's also presumably less efficient that returning a const reference to the underlying object.

Input Data

{ { "$schema": "http://json-schema.org/draft-06/schema#", "$ref": "#/definitions/foo", "definitions": { "coordinate": { "type": "object", "required": [ "latitude", "longitude" ], "additionalProperties": false, "properties": { "latitude": { "type": "number" }, "longitude": { "type": "number" } } }, "coordinates": { "type": "array", "items": { "$ref": "#/definitions/coordinate" } }, "foo": { "type": "object", "required": [ "coordinates-required" ], "additionalProperties": false, "properties": { "coordinates": { "$ref": "#/definitions/coordinates" }, "coordinates-required": { "$ref": "#/definitions/coordinates" }, "bar" : { "type": "number" } } } } }

Expected Behaviour / Output

const boost::optional<std::vector<Coordinate>>& get_coordinates() const { return coordinates; }

Current Behaviour / Output

boost::optional<std::vector<Coordinate>> get_coordinates() const { return coordinates; }

Steps to Reproduce

Using above schema;
quicktype --lang c++ -s schema --out ./test.h ./test.schema.json
(or insert into app.quicktype.io)

Possible Solution