Serialization In DepthTim 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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