storing the value in a temporary variable problem

Question

Hello people, i want to make a pinball game fully in C#, i am using the gameion pinball template but rewrite it in C#. i run into the following problem when firing the pinball:

if (CanUse == true) { ControlBallLaunchByKeyboard(); } else { // Spring resets back to normal position if (ballLaunch.localScale.y < 12) {

         ballLaunch.localScale.y = (ballLaunch.localScale.y + 12.0f) * 0.5f;
         ballLaunch.position.y = (ballLaunch.position.y - 63.00549f) * 0.5f;
     }        
     }
 }
 
 
 private void  ControlBallLaunchByKeyboard (){
 if (Input.GetKey(KeyCode.DownArrow))
 {
     // When the player holds down the Down Arrow button, pull down the ball launch
     if (ballLaunchForce < 2000)
     {
         float dt = Time.deltaTime * 8.0f;
         ballLaunchForce += dt * 180;
         ballLaunch.localScale.y = Mathf.Lerp(12.8f, 1.8f, ballLaunchForce / 2000);
         ballLaunch.position.y = Mathf.Lerp(-63.1f, -68.6f, ballLaunchForce / 2000);
     }
 }
 else
 {
     // Spring resets back to normal position
     if (ballLaunch.localScale.y < 12) 
     {
         ballLaunch.localScale.y = (ballLaunch.localScale.y + 12.0f) * 0.5f;
         ballLaunch.position.y = (ballLaunch.position.y - 63.00549f) * 0.5f;
     }
 }

i get allot of the following errors: - Assets/Scripts/Trig.cs(43,36): error CS1612: Cannot modify a value type return value of UnityEngine.Transform.localScale'. Consider storing the value in a temporary variable - Assets/Scripts/Trig.cs(44,36): error CS1612: Cannot modify a value type return value of UnityEngine.Transform.position'. Consider storing the value in a temporary variable

Could anyone point out what i am doin wrong or help me ??

thanks in advance

Answer 1

Answer by moichezmoi · Mar 29, 2012 at 08:48 AM

Hi,

transform.localScale and transform.position are properties, in C#. So, you can get those vector3, you can set those vector3, but you can't dirrectly modify members of those vector3.

A solution is to use a temporary variable, and replace lines like :

 ballLaunch.localScale.y = (ballLaunch.localScale.y + 12.0f) * 0.5f;

by

 Vector3 temp = ballLaunch.localScale;
 temp.y = (ballLaunch.localScale.y + 12.0f) * 0.5f;
 ballLaunch.localScale = temp;

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Trevus · Mar 29, 2012 at 10:55 AM 0

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Thanks MoichezMoi,

I inserted your solution, and it worked. The errors are gone now.

Some new ones arrived when i start the game. Do you know what it means?

what i am ingame trying to do is when arrowkey down is pressed it should build up force and show the spring pulling back and then when release the spring resets and gives the ball force.

NullReferenceException UnityEngine.Transform.get_localScale () (at C:/BuildAgent/work/842f9557127e852/Runtime/ExportGenerated/Editor/UnityEngineTransform.cs:78) Trig.Update () (at Assets/Scripts/Trig.cs:40)

when i click on the error, it says the error lies somewhere here: if (ballLaunch.localScale.y < 12)

Bunny83 · Mar 29, 2012 at 10:58 AM 2

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I would guess your "ballLaunch" variable is not set to any object. Where do you assign a Transform to it?

erickalvessud · Oct 08, 2013 at 02:45 AM 0

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Thank you man. You helped me too.

marcfielding · Jan 10, 2014 at 01:16 AM 0

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Helped me too thanks a lot!

RyanPate52 · Feb 01, 2015 at 05:45 AM 0

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Thanks for the help!

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storing the value in a temporary variable problem

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