beatthat / safe-refs

Use safe refs to hold references to Unity components that may be destroyed. An instance of SafeRef<MyComponent>.value will be null if the component or it's GameObject has been destroyed.

When components keep references to other components, it's easy to end up with null pointer problems. SafeRefs are a simple way to always know whether a component reference is valid.

Install

From your unity project folder:

npm init --force # only if you don't yet have a package.json file
npm install --save beatthat/safe-refs

The package and all its dependencies will be installed under Assets/Plugins/packages.

In case it helps, a quick video of the above: https://youtu.be/Uss_yOiLNw8

Usage

An instance of SafeRef.value will be null if the component or its GameObject has been destroyed.

MyComponent someComponent = GetComponentsInChildren<MyComponent>();

var ref = new SafeRef<MyComponent>(someComponent);

// ref.value will return someComponent
Destroy(someComponent.gameObject);
// ref.value will return null

...SafeRefs are structs to handle them accordingly

public class HandlesStructCorrectly
{
  public void SetComponent(MyComponent c) {
    m_ref = new SafeRef<MyComponent>(c);
  }
  private SafeRef<MyComponent> m_ref;
}

public class HandlesStructIncorrectly
{
  public void SetComponent(MyComponent c) {
    var ref = m_ref; // ref is a copy of m_ref, no longer a reference to the same thing
    ref.value = c; // m_ref has not changed

    // the example above is contrived
    // but just to illustrate the point
    // that you need to be careful
    // to avoid editing copies of struct
  }
  private SafeRef<MyComponent> m_ref;
}