Allow creation of box and ref through std::unique_ptr and std::shared…

…_ptr respectively

docs/rfl_ref.md

@@ -138,6 +138,16 @@ This will result in the following JSON string:
 {"leafOrNode":{"type":"Node","criticalValue":10.0,"lesser":{"leafOrNode":{"type":"Leaf","value":3.0}},"greater":{"leafOrNode":{"type":"Leaf","value":5.0}}}}
 ```
 
+You can also initialize `rfl::Box<T>` from a `std::unique_ptr<T>`:
+
+```cpp
+auto ptr = std::make_unique<std::string>("Hello World!");
+const rfl::Result<rfl::Box<std::string>> box = rfl::make_box<std::string>(std::move(ptr));
+```
+
+Note that `box` is wrapped in a `Result`. That is, because we cannot guarantee at compile time 
+that `ptr` is not `nullptr`, therefore we need to account for that.
+
 If you want to use reference-counted pointers, instead of unique pointers, you can use `rfl::Ref`. 
 `rfl::Ref` is the same concept as `rfl::Box`, but using `std::shared_ptr` under-the-hood.
 

include/rfl/Box.hpp

@@ -4,6 +4,8 @@
 #include <memory>
 #include <stdexcept>
 
+#include "Result.hpp"
+
 namespace rfl {
 
 /// The Box class behaves very similarly to the unique_ptr, but unlike the
@@ -20,6 +22,15 @@ class Box {
     return Box<T>(std::make_unique<T>(std::forward<Args>(_args)...));
   }
 
+  /// You can generate them from unique_ptrs as well, in which case it will
+  /// return an Error, if the unique_ptr is not set.
+  static Result<Box<T>> make(std::unique_ptr<T>&& _ptr) {
+    if (!_ptr) {
+      return Error("std::unique_ptr was a nullptr.");
+    }
+    return Box<T>(std::move(_ptr));
+  }
+
   Box() : ptr_(std::make_unique<T>()) {}
 
   Box(const Box<T>& _other) = delete;
@@ -77,7 +88,7 @@ class Box {
 
 /// Generates a new Ref<T>.
 template <class T, class... Args>
-Box<T> make_box(Args&&... _args) {
+auto make_box(Args&&... _args) {
   return Box<T>::make(std::forward<Args>(_args)...);
 }
 

include/rfl/Ref.hpp

@@ -4,6 +4,8 @@
 #include <memory>
 #include <stdexcept>
 
+#include "Result.hpp"
+
 namespace rfl {
 
 /// The Ref class behaves very similarly to the shared_ptr, but unlike the
@@ -20,6 +22,24 @@ class Ref {
     return Ref<T>(std::make_shared<T>(std::forward<Args>(_args)...));
   }
 
+  /// You can generate them from shared_ptrs as well, in which case it will
+  /// return an Error, if the shared_ptr is not set.
+  static Result<Ref<T>> make(std::shared_ptr<T>&& _ptr) {
+    if (!_ptr) {
+      return Error("std::shared_ptr was a nullptr.");
+    }
+    return Ref<T>(std::move(_ptr));
+  }
+
+  /// You can generate them from shared_ptrs as well, in which case it will
+  /// return an Error, if the shared_ptr is not set.
+  static Result<Ref<T>> make(const std::shared_ptr<T>& _ptr) {
+    if (!_ptr) {
+      return Error("std::shared_ptr was a nullptr.");
+    }
+    return Ref<T>(_ptr);
+  }
+
   Ref() : ptr_(std::make_shared<T>()) {}
 
   Ref(const Ref<T>& _other) = default;
@@ -87,7 +107,7 @@ class Ref {
 
 /// Generates a new Ref<T>.
 template <class T, class... Args>
-Ref<T> make_ref(Args&&... _args) {
+auto make_ref(Args&&... _args) {
   return Ref<T>::make(std::forward<Args>(_args)...);
 }
 

tests/json/test_box2.cpp

@@ -0,0 +1,27 @@
+#include <cassert>
+#include <iostream>
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <source_location>
+#include <string>
+#include <vector>
+
+#include "test_box.hpp"
+
+namespace test_box2 {
+
+void test() {
+  std::cout << std::source_location::current().function_name() << std::endl;
+
+  auto ptr = std::make_unique<std::string>("Hello World!");
+  const rfl::Result<rfl::Box<std::string>> box =
+      rfl::make_box<std::string>(std::move(ptr));
+
+  if (box) {
+    std::cout << "OK" << std::endl << std::endl;
+  } else {
+    std::cout << "Expected the result to be successful." << std::endl
+              << std::endl;
+  }
+}
+}  // namespace test_box2

tests/json/test_box2.hpp

@@ -0,0 +1,4 @@
+namespace test_box2 {
+void test();
+}
+

tests/json/tests.cpp

@@ -10,6 +10,7 @@
 #include "test_as2.hpp"
 #include "test_as_flatten.hpp"
 #include "test_box.hpp"
+#include "test_box2.hpp"
 #include "test_c_array_class1.hpp"
 #include "test_c_array_class2.hpp"
 #include "test_c_array_class3.hpp"
@@ -98,6 +99,7 @@ int main() {
   test_field_variant::test();
   test_ref::test();
   test_box::test();
+  test_box2::test();
   test_array::test();
   test_timestamp::test();
   test_flatten::test();