Documentation

Unity Engine

User Manual

Script Reference

Unity Engine

OnOpenAssetAttribute

Invokes a static callback method when the Unity Editor attempts to open an asset.
Read time 5 minutesLast updated 6 days ago

Definition

public sealed class OnOpenAssetAttribute : CallbackOrderAttribute

Remarks

Unity calls any static method decorated with 
[OnOpenAssetAttribute]
when attempting to open an asset, such as when double-clicking the asset in the Editor. This offers the opportunity to implement custom asset opening logic or to verify that an asset can open in the Unity Editor as opposed to an external program.
The attribute targets methods and accepts two optional positional parameters:
  • callbackOrder
    : The first parameter represents the index of the callback invocation order and must be of type 
    int
    . This is useful if you have more than one OnOpenAssetAttribute callbacks, and you would like them to be called in a certain order. Methods are called in ascending numerical order, starting from 0.
  • attributeMode
    : The second parameter is an 
    enum
    value from OnOpenAssetAttributeMode that indicates whether the decorated method is called in 
    Execute
    or 
    Validate
    mode. 
    Execute
    mode is intended for callbacks that implement some custom asset-opening behavior. 
    Validate
    mode is intended to check if the Editor can open the asset. If not specified the default mode is OnOpenAssetAttributeMode.Execute.
A method decorated with 
[OnOpenAssetAttribute]
and in 
Execute
mode must have one of the following signatures:
  • static bool OnOpenAsset(EntityId entityId)
  • static bool OnOpenAsset(EntityId entityId, int line)
  • static bool OnOpenAsset(EntityId entityId, int line, int column)
Note: The callback method does not have to be named 
OnOpenAsset
but its signature must match one of those shown.
A method decorated with 
[OnOpenAssetAttribute]
and in 
Validate
mode must have the following signature:
static bool OnOpenAsset(EntityId entityId)
In OnOpenAssetAttributeMode.Validate mode, the method does not open the asset but checks to see if the Editor can open it. It returns 
true
if the Editor can open the asset or 
false
otherwise. This is equivalent to the check AssetDatabase.CanOpenAssetInEditor performs.
Version control system integrations primarily use this validation function to determine what files to check out. Native assets like GameObjects, Scenes, or user-made assets return 
true
because they are opened and edited in the Editor. Assets like sound clips and textures return 
false
because they're opened and edited in an external program.
See Also: OnOpenAssetAttributeMode, AssetDatabase.CanOpenAssetInEditor

Examples

// Return true if you handled the opening of the asset or false if an external tool should open it.using UnityEngine;using UnityEditor;using UnityEditor.Callbacks;public class MyAssetHandler : ScriptableObject{    [OnOpenAssetAttribute(1)]    public static bool step1(EntityId entityId, int line)    {        string name = EditorUtility.EntityIdToObject(entityId).name;        Debug.Log("Open Asset step: 1 (" + name + ")");        return false; // we did not handle the open    }    // step2 has an attribute with index 2, so will be called after step1    [OnOpenAssetAttribute(2)]    public static bool step2(EntityId entityId, int line)    {        Debug.Log("Open Asset step: 2 (" + entityId + ")");        return false; // we did not handle the open    }    [OnOpenAsset(OnOpenAssetAttributeMode.Validate)]    public static bool WillOpenInUnity(EntityId entityId)    {        if (AssetDatabase.GetMainAssetTypeAtPath(AssetDatabase.GetAssetPath(entityId)) == typeof(MyAssetHandler))        {            // We can open MyAssetHandler asset using MyAssetHandler opening method            return true;        }        else  return false; // The passed instance doesn't belong to MyAssetHandler type asset so we won't be able to open it using opening method inside MyAssetHandler    }}

Inheritance

Inherited Members