Automatic binding of component references

AutoComponentAttribute.cs

// MIT License
// 
// Copyright (c) 2018 Sabresaurus
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// 	The above copyright notice and this permission notice shall be included in all
// 	copies or substantial portions of the Software.
// 
// 	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// 	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// 	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// 	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// 	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// 	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// 	SOFTWARE.

using UnityEngine;
using System;
using System.Reflection;
using System.Collections.Generic;

public enum RecursiveDirection { None, Down, Up };

public class AutoComponent : Attribute
{
	RecursiveDirection direction = RecursiveDirection.None;
	bool includeInactive = false;

	public AutoComponent()
	{}

	public AutoComponent(RecursiveDirection direction)
	{
		this.direction = direction;
	}

	public AutoComponent(RecursiveDirection direction, bool includeInactive)
	{
		this.direction = direction;
		this.includeInactive = includeInactive;
	}

	private static List<FieldInfo> GetFieldsRecursively(Type type)
	{
		List<FieldInfo> fields = new List<FieldInfo>();
		fields.AddRange(type.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance));

		// NonPublic binding flags only returns fields on the current inheritance level, therefore we must recurse through the superclasses to get them all
		Type baseType = type.BaseType;
		while (baseType != null)
		{
			// Add the non-public fields on the superclass
			fields.AddRange(baseType.GetFields(BindingFlags.NonPublic | BindingFlags.Instance));

			// Get the next superclass
			baseType = baseType.BaseType;
		}

		return fields;
	}

	public static void Setup(MonoBehaviour behaviour)
	{
		List<FieldInfo> fields = GetFieldsRecursively(behaviour.GetType());

		for (int i = 0; i < fields.Count; i++) 
		{
			object[] customAttributes = fields[i].GetCustomAttributes(typeof(AutoComponent), false);

			if(customAttributes.Length > 0)
			{
				RecursiveDirection recursiveDirection = (customAttributes[0] as AutoComponent).direction;

				// If this is an array or list
				if (typeof(Array).IsAssignableFrom(fields[i].FieldType))
				{
					Type elementType = fields[i].FieldType.GetElementType();

					Component[] components;
					if(recursiveDirection == RecursiveDirection.Down)
					{
						components = behaviour.GetComponentsInChildren(elementType, (customAttributes[0] as AutoComponent).includeInactive);
					}
					else if(recursiveDirection == RecursiveDirection.Up)
					{
						components = behaviour.GetComponentsInParent(elementType, (customAttributes[0] as AutoComponent).includeInactive);
					}
					else
					{
						components = behaviour.GetComponents(elementType);
					}
					Array array = Array.CreateInstance(elementType, components.Length);

					for (int j = 0; j < components.Length; j++) 
					{
						array.SetValue(components[j], j);
					}
					fields[i].SetValue(behaviour, array);
				}
				else
				{
					if(recursiveDirection == RecursiveDirection.Down)
					{
						fields[i].SetValue(behaviour, behaviour.GetComponentInChildren(fields[i].FieldType, (customAttributes[0] as AutoComponent).includeInactive));
					}
					else if(recursiveDirection == RecursiveDirection.Up)
					{
						fields[i].SetValue(behaviour, behaviour.GetComponentInParent(fields[i].FieldType));
					}
					else
					{
						fields[i].SetValue(behaviour, behaviour.GetComponent(fields[i].FieldType));
					}
				}
			}
		}
	}
}