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Event 2.0: one-line UnityEvent with cross-scene targets

UnityEvent​

A UnityEvent with one call: a header, two lines and a footer

A header, two lines for a single call, a footer with "+" and "-".

Event 2.0​

The same call on one line

The same call, on one line.

UnityEvent is one of the most useful things in Unity: a designer wires a button to a function without a line of code. It is also one of the most frustrating fields of the inspector: it takes a lot of room, it accepts one argument at most, and it can only point at objects of its own scene.

Event 2.0 (the class is called UnityEssentialEvent) is the event I now use in its place. It is declared and invoked the same way:

[SerializeField] private UnityEssentialEvent _onOpen;

private void Open()
{
    _onOpen?.Invoke();
}

1. It shows more than a UnityEvent can​

A UnityEvent only lists the functions with no argument, or with one argument that is an int, a float, a string, a bool or an object. Everything else is hidden from the list. UnityEssentialEvent lists them too.

A bool stays on the line​

AnimateScale.SetLoop with its checkbox at the end of the line

A call with a single bool keeps one line: its checkbox sits at the end.

Vectors, colours and friends​

Transform.localPosition with its X, Y and Z fields

Vector2, Vector3, Vector4, their Int versions, Color, Quaternion and LayerMask are drawn with their usual fields. Here the event sets Transform.localPosition, which a UnityEvent cannot do.

Enums​

Transform.hideFlags with a dropdown of its values

An enum argument is a dropdown of its values.

Several arguments​

Transform.LookAt with its target and worldUp arguments

A function can take several arguments, up to ten, each on its own line with its name. Here Transform.LookAt(target, worldUp).

2. One line per call​

The display was redone around one rule: a call is one line.

[when] [target] [function] ............ [trash] [+]

On that line: when it runs (play mode or editor too), target, function, a trash button. Hover the name to invoke it right now; right click to copy its calls. On a component with five events, it is the difference between seeing everything and scrolling.

3. Targets in another scene​

Unity does not let an object keep a link to an object of another scene. In a project made of several scenes loaded together (a core scene, the UI, a level), that is a daily wall.

I already had a way around it: the GuidComponent, shown in Scene Context Loader. It gives a GameObject an identity that survives closing and reopening scenes. UnityEssentialEvent now uses it by itself: drop an object of another scene on a call and the link is made by its Guid. If the object has no GuidComponent yet, one is added for you.

The colour tells the state: blue, found in another scene; yellow, its scene is not loaded (skipped, with a warning); red, deleted.

Six calls, numbered from 1 to 6

A call on a Guid target is looked up again each time the event is invoked: a target appears with its scene and disappears with it, with no code to write.

PS, attention to detail: drag an object from the hierarchy and drop it on an event with no call, and the first call is created with this object as its target. Same scene: a direct link. Another scene: a Guid link. One gesture in both cases.

info

UnityEssentialEvent is part of Unity Essentials, my toolbox for the Kugle Corp games. Contact me if you are interested.

See also​