The document discusses serialization in Unity, including how it works, how to serialize classes and class references, using ScriptableObjects, and working with assets and sub-assets. It covers marking classes as serializable, using attributes like SerializeField, and ensuring data survives assembly reloads by properly implementing serialization.

1. Serialization In Depth
Tim Cooper
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Who Am I?
• Developer at Unity
• Used to make games!
• Bioshock 1 / 2
• Responsible for:
• Editor features
• Graphics features
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Topics
• Overview
• How serialization works
• How to serialize
• Classes
• Class References
• ScriptableObject
• Arrays
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Topics
• Working with Assets
• Creating an asset
• Custom GUI for assets
• Using an asset at runtime
• Sub-assets
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Overview
• Why write nicely serializable classes?
• Editor windows will survive assembly reload
• Ability to save data as custom asset files
• Easier the writing your own
• Once you know how it works ;)
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Overview
• When does serialization happen?
• On assembly reload
• Script recompilation
• Enter / exit play mode
• Loading and saving the project / scene
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How serialization works
• Assembly reload
• Pull all data out of managed (mono) land
• Create internal representation of the data on C++ side
• Destroy all memory / information in managed land
• Reload assemblies
• Reserialize the data from c++ into managed
• If your data does not make it into c++ it will go away!
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Serializing Classes
• A simple class will not automatically serialize!
• Unity does not know if the class is meant to serialize or not!
• We can fix this!
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Serializing Classes
• A class needs to be marked up to serialize
• [Serializable]
• Field serialization rules
• public - always serialize
• private / protected - serialize on assembly reload (editor)
• static - never serialize
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Serializing Classes
• Field serialization modifiers
• [SerializeField] - Make private / protected fields serialize
• [NonSerialized] - Never serialize the field
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Serializing Structs
• User structs don’t serialize
• A few built in ones do
• Don’t use them for serialization!
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Serializing Class References
• Normal class references
• Each reference serialized individually
• When you deserialize... you have different members
• Think of them as behaving like structs!
• Use them when you have:
• Data that is references only once
• Nested data
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Serializing ScriptableObject
• Serialize as reference properly!
• Multiple references to this object
• Will resolve properly on deserialization
• Supports some Unity callbacks
• OnEnable, OnDisable, OnDestroy
• Create them with CreateInstance <type> ()
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Serializing ScriptableObject
• Use them when you want data
• That is referenced multiple times
• Shared data
• Needs Unity system callbacks
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Serializing ScriptableObject
• Initialization order
• Instance created
• Fields deserialized into object
• If they exist on the c++ side ;)
• OnEnable() Called
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Serializing ScriptableObject
• To create fields properly inside a SO
• Don’t create them in constructor
• Check if they are null in OnEnable ()
• If not null... then they were deserialized
• if null... create them!
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Hideflags
• Control visibility
• Important if you are NOT saving the asset or holding a reference to it
• i.e editor only data structure referenced by a window
• HideAndDontSave
• No asset / scene root - tells unity to consider this a root object
• Will not get cleaned up on scene load (play mode)
• Destroy using Destroy ()
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Serializing Concrete Arrays
• Works as expected
• No object sheering
• Serialized and deserialized properly
• More complex objects?
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Serializing Base Class Arrays
• Does not work as expected
• Breaks on deserialization
• Object shearing occurs
• How can we serialize more complex hierarchies?
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Serializing General Array
• ScriptableObject Array!
• Serializes as references...
• Will serialize as expected
• Only need to set hideflags on ‘the most root’ object
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Asset Creation
• Design the class you want to be an asset
• Database, Character Info, ect
• Ensure that the ‘root’ is a ScriptableObject
• An asset file is a ScriptableObject
• Create the assed by calling
• AssetDatabase.CreateAsset (object, “location.asset”)
• If is mandatory to use the .asset file extension
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Custom Asset UI
• Your asset is just like a Unity asset!
• You can write custom editors
• [CustomEditor (typeof (YourType))]
• Extend from the EditorClass
• Remember to put in in an editor folder!
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Property Fields
• Delegate drawing to a separate class
• Useful for custom controls
• Can be implicitly linked to a class
• [CustomPropertyDrawer (typeof (MyType))]
• Does not need to be marked up per field
• Can be hooked up via an attribute
• Marked on a per field basis!
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Property Fields
• How?
• [CustomPropertyDrawer (typeof (MyType))]
• Extend PropertyDrawer
• Need a custom height?
• Override GetPropertyHeight ()
• Do your custom drawing
• OnGUI ()
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Using Assets
• Create a reference to the type
• Can be anywhere:
• EditorWindow
• MonoBehaviour
• Connect it to an asset
• Via code of the inspector
• Do game specific things!
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Using Sub-Assets
• ScriptableObjects
• Save each manually... they won’t serialize to file all the way down
• How?
• Add them as children of another asset (AddObjectToAsset)
• By default it will show all assets as sub assets
• Set HideFlags to HideFlags.HideInHierarchy
• Much nicer :)
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Using Sub-Assets
• Use SubAssets for complex data structures
• Where many elements are ScriptableObjects
• Graphs
• Databases
• ect!
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