What is #pragma implicit and #pragma downcast

Unity Engine
1

In the process of automatically converting my 2.6 project into 3.0, Unity has added

#pragma implicit
#pragma downcast

to all my scripts. Does anyone know why and what these do? The shipped help docs don’t say anything about these.

Thanks!

2

#pragma implicit allows you to implicitly declare variables when using #pragma strict.

#pragma strict
foo = 5; // no!

#pragma strict
var foo = 5; // yes!

#pragma strict
#pragma implicit
foo = 5; // yes!

#pragma downcast allows casting from a super type to a sub type when using #pragma strict.

#pragma strict
var go : GameObject;
var clone : GameObject = Instantiate(go); // no!  Instantiate returns Object, not GameObject

#pragma strict
#pragma downcast
var go : GameObject;
var clone : GameObject = Instantiate(go); // yes!

#pragma strict
var go : GameObject;
var clone : GameObject = Instantiate(go) as GameObject; // yes!

The #pragma strict in Unity 2.6 wasn’t as strict, so it was essentially using downcast and implicit.

–Eric

3

?

Doesn’t #pragma implicit nullify #pragma strict ?

4

Eh? No…

#pragma strict

function Start () {
	var foo = GetComponent(Transform);
	foo.position.x = 100.0;  // no!  Can't use dynamic typing with #pragma strict!
}

#pragma implicit wouldn’t have any effect there. (Might want to use #pragma downcast though, depending on how you fix the dynamic typing.)

–Eric

5

What’s wrong with this line ? We just assign 100.0 to the x variable of a transform.position :expressionless:

6

“foo” has no type, i.e. is not explicitly a Transform.

7

Try the code and see what the error is.

Actually no, GetComponent returns Component, so “foo” is of type Component, which has no position variable.

–Eric

8

So what is the best procedure then? To use #pragma downcast, or to adjust the line to not return a Component but a Transform? Code like the following (from the documentation) no longer work without having #pragma downcast.

var mesh : Mesh = new Mesh ();
GetComponent(MeshFilter).mesh = mesh;

So, without using a #pragma downcast, how would I tweak that so I don’t get the error about Component not having a .mesh attribute?

9 
(GetComponent(MeshFilter) as MeshFilter).mesh = mesh;

Or use generics:

GetComponent.<MeshFilter>().mesh = mesh;

–Eric

10

Hey guys, just wondering, in your sections of example code, you have #pragma strict on multiple lines. I thought it only had to be stated once at the top of each script?

11

Those are meant to be separate examples.

–Eric

12

Got it. thought I might have been missing something there for a sec :slight_smile:

13

how would be this for enabling script, for example I want to disable/enable script “chack” attached to game object. I have such line: child.gameObject.GetComponent("chack").enabled=true;and it gives me such error: ‘enabled’ is not a member of ‘UnityEngine.Component’. when I write: child.gameObject.GetComponent.<"chack">().enabled=true; it gives me this error: Unexpected token: chack.

14

heh, it doesn’t need quotes :smile:
child.gameObject.GetComponent.().enabled=true;