Error on converting UnityScript to C#

Question

I am trying to convert some UnityScript code to D# and I am getting the following error:

Expression denotes a method group, where a variable, value or type was expected on the Getcomponent

void  Update ()
{
    float xVel = GetComponent().Rigidbody2D().velocity.x;
    if( xVel < 18 && xVel > -18 && xVel !=0){
        if(xVel > 0){
            GetComponent.Rigidbody2D().velocity.x=20;   

        }else{
            GetComponent.Rigidbody2D().velocity.x = -20;

        }
    }
}

Getomponet is an inbuilt method in unity docs.unity3d.com/ScriptReference/Component.GetComponent.html — Student
– Student, Commented Jun 25, 2015 at 11:39

mGuv · Accepted Answer · 2015-06-25 12:03:55Z

5

Your issue is with: GetComponent().Rigidbody2D() as that is not how you use GetComponent, the error you are seeing is probably because GetComponent requires a parameter or a specified type. The JS and C# GetComponent work a little different. You probably mean to do:

void  Update ()
{
    float xVel = GetComponent<Rigidbody2D>().velocity.x;
    if( xVel < 18 && xVel > -18 && xVel !=0){
        if(xVel > 0){
            GetComponent<Rigidbody2D>().velocity.x = 20;   

        }else{
            GetComponent<Rigidbody2D>().velocity.x = -20;

        }
    }
}

Also in C#, I don't think you can modify the velocity directly, due to the property wrappers around it. Instead you have to manually update the velocity to a new Vector2. If you only want to set the x value, pass in the existing y value.

I would write it something like this:

private Rigidbody2D _rigidBody;

void Start()
{
    _rigidBody = GetComponent<Rigidbody2D>();
}

void  Update ()
{
    float xVel = _rigidBody.velocity.x;
    if( xVel < 18 && xVel > -18 && xVel !=0){
        if(xVel > 0){
            _rigidBody.velocity = new Vector2(20, _rigidBody.velocity.y);   

        }else{
            _rigidBody.velocity = new Vector2(-20, _rigidBody.velocity.y);   
        }
    }
}

Though I'd change that magic 18 in to a variable too but I can't make a guess here as to what it represents!

edited Jun 25, 2015 at 12:03

answered Jun 25, 2015 at 11:53

mGuv

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6 Comments

Student Over a year ago

It still gives me this error : Cannot modify a value type return value of `UnityEngine.Rigidbody2D.velocity'. Consider storing the value in a temporary variable

mGuv Over a year ago

I think velocity cannot be modified manually. You will need to do: _rigidBody.velocity = new Vector2(newXHere, _rigidBody.velocity.y);

Student Over a year ago

sorry to bother you but you have been really helpful i am getting an error about this code _rigidBody.velocity = new Vector2(y/2, _rigidBody.velocity.x) + colInfo.collider.GetComponent<Rigidbody2D>().velocity.y/3; its saying The best overloaded method match for UnityEngine.Vector2.Vector2(float, float)' has some invalid arguments and Argument #1' cannot convert object' expression to type float'

mGuv Over a year ago

That's because you're trying to add the left hand side, which is a Vector2 to just y/3 which is a float. Totally assuming here that you mean:

_rigidBody.velocity = new Vector2(y/2, _rigidBody.velocity.x) + new Vector2(0, colInfo.collider.GetComponent<Rigidbody2D>().velocity.y/3);

I may have got the x/y the wrong way round but that's the best guess I can make.

Student Over a year ago

and again :( : 1.The name y' does not exist in the current context , 2.The best overloaded method match for 3.UnityEngine.Vector2.Vector2(float, float)' has some invalid arguments Argument #1' cannot convert object' expression to type `float'

|

Casper Kleintjes · Accepted Answer · 2015-06-25 11:54:21Z

2

float xVel = GetComponent<Rigidbody2D>().velocity.x;

GetComponent is used like this.

answered Jun 25, 2015 at 11:54

Casper Kleintjes

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