# LazyLoadReference<T>

> Serializable lazy reference to a UnityEngine.Object contained in an asset file.

## Definition

* **Type:** Struct
* **Namespace:** [UnityEngine](/engine/6000.0/script-reference/unityengine.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public struct LazyLoadReference<T> where T : Object
```

## Remarks

Allows an asset to reference another asset but delays loading the referenced asset until it is used, instead of loading it when the referencing object is deserialized.

**Typical use cases**:

* For importer settings that need to reference assets but reading the settings from disk cannot load the referenced assets because they may not be imported and are not yet accessible.

* For reducing the time it takes to open a scene by loading only the assets needed for the initial set up, or display, in Edit Mode.

**Notes:**

* A lazy reference has a slight performance overhead compared to a direct reference.

* In a standalone player, all assets are loaded when the player is loaded, or when asset bundles are loaded.

## Examples

```csharp
using UnityEditor.AssetImporters;
using UnityEngine;

[ScriptedImporter(1, "foo")]
public class FooImporter : ScriptedImporter
{
    public LazyLoadReference<Material> m_DefaultMaterial;

    public override void OnImportAsset(AssetImportContext ctx)
    {
        // At this point, 'm_DefaultMaterial' may refer to a material that has yet to be loaded into memory

        Material mat;
        if (!m_DefaultMaterial.isSet) // 'isSet' Does not load the referenced material even if not in memory.
        {
            mat = new Material(Shader.Find("Transparent/Diffuse"));
            ctx.AddObjectToAsset("mat", mat);
        }
        else
        {
            mat = m_DefaultMaterial.asset; // Will load referenced material if it is not already in memory.
        }

        var obj = GameObject.CreatePrimitive(PrimitiveType.Cube);
        obj.transform.GetComponent<MeshRenderer>().material = mat;

        ctx.AddObjectToAsset("main", obj);
        ctx.SetMainObject(obj);
    }
}
```

## Constructors

| Constructor                                                                                                                           | Description                        |
| ------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------- |
| [LazyLoadReference\`1(\`0)](/engine/6000.0/script-reference/unityengine/lazyloadreference1/ctor.md#lazyloadreference\(t\))            | Construct a new LazyLoadReference. |
| [LazyLoadReference\`1(System.Int32)](/engine/6000.0/script-reference/unityengine/lazyloadreference1/ctor.md#lazyloadreference\(int\)) | Construct a new LazyLoadReference. |

## Properties

| Property                                                                                   | Description                                                                                                                         |
| ------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------- |
| [asset](/engine/6000.0/script-reference/unityengine/lazyloadreference1/asset.md)           | Accessor to the referenced asset.                                                                                                   |
| [instanceID](/engine/6000.0/script-reference/unityengine/lazyloadreference1/instanceid.md) | Returns the instance id to the referenced asset.                                                                                    |
| [isBroken](/engine/6000.0/script-reference/unityengine/lazyloadreference1/isbroken.md)     | Convenience property that checks whether the reference is broken: refers to an object that is either not available or not loadable. |
| [isSet](/engine/6000.0/script-reference/unityengine/lazyloadreference1/isset.md)           | Determines if an asset is being targeted, regardless of whether the asset is available for loading.                                 |