public/lib/component/cpp/exposed_object.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_COMPONENT_CPP_EXPOSED_OBJECT_H_
#define LIB_COMPONENT_CPP_EXPOSED_OBJECT_H_

#include "object_dir.h"

#include <lib/fxl/macros.h>

namespace component {

// |ExposedObject| is a base class that exposes an |ObjectDir| interface to
// derived classes. It automatically handles lifecycle management, namely
// removing itself from a parent |Object| at destruction time.
//
// This is the preferred mechanism to expose a long-lasting object hierarchy for
// inspection.
class ExposedObject {
 public:
  // Static method for generating unique names with a given prefix.
  // Every child object requires a unique name; if you don't necessarily care
  // about the names of child objects use this method to generate a unique one.
  // Example: UniqueName("table_entry") -> "table_entry:0xa".
  static std::string UniqueName(const std::string& prefix);

  // Constructs a new exposed object with the given name. Call this constructor
  // from derived class constructors.
  explicit ExposedObject(const std::string& name);

  // Wrap an existing ObjectDir as an ExposedObject.
  explicit ExposedObject(ObjectDir object_dir);

  virtual ~ExposedObject();

  ExposedObject(ExposedObject&& other) = default;
  ExposedObject& operator=(ExposedObject&& other);

  // Adds a child to this object.
  void add_child(ExposedObject* child);

  // Explicitly set the parent of this object. This method handles removing the
  // object from its current parent, if any, and attaching it to the new parent.
  void set_parent(const ObjectDir& parent);

  // Remove this object from its parent.
  void remove_from_parent();

  // Gets the |ObjectDir| representation of this object.
  ObjectDir object_dir() const { return object_dir_; }

  // Gets the |Object| this is wrapping.
  fbl::RefPtr<Object> object() const { return object_dir_.object(); }

 private:
  // Helper to move this object to a different parent.
  void move_parents(const ObjectDir& new_parent);

  // The object's current parent, if any.
  ObjectDir parent_;

  // The object itself, accessible through object().
  ObjectDir object_dir_;

  FXL_DISALLOW_COPY_AND_ASSIGN(ExposedObject);
};

}  // namespace component

#endif  // LIB_COMPONENT_CPP_EXPOSED_OBJECT_H_