Can I modify a property's property in a single line?

Question

In unity, when I try to do the following;

gameObject1.GetComponent<ParticleSystem>().main.startSize = transform.localScale.x / 5;

It says;

Cannot change the return value of "ParticleSyste.main" because it is not a variable.

But if I try to do the following;

var particleSystemMain = gameObject1.GetComponent<ParticleSystem>().main;
particleSystemMain.startSize = transform.localScale.x / 5;

it works. Why cannot I directly modify a propert's property?

Also, Unity documentation does this in the second way: https://docs.unity3d.com/ScriptReference/ParticleSystem.MainModule-startSize.html

Getting the `main` or `GetComponent()` method has some side effects on `transform` I think. You should check it's implementation. — Sarvesh Mishra, Mar 17 '19 at 08:03
Possible duplicate of [Cannot modify the return value error c#](https://stackoverflow.com/questions/1747654/cannot-modify-the-return-value-error-c-sharp) — Draco18s no longer trusts SE, Mar 17 '19 at 21:58

score 3 · Accepted Answer · answered Mar 17 '19 at 08:58

When you assign main to var particleSystemMain, you actually get a copy of it. It's not that the action is not technically possible, but it will not change the main in your partical system, and your modified copy is not saved under any form, so c# straight up forbids it.

See this similar question for a slightly deeper explanation

Can I modify a property's property in a single line?

1 Answers1