Variable name confusion

I am trying to create a boolean variable called 3D_pressed;
But I am getting an error which states
"error CS1519: Unexpected symbol `3' in class, struct, or interface member declaration". How do I solve this?

 

You cannot define variables or methods that starts with a digit in C#.
I recommend adopting either Unity naming standard, or Microsoft one.

E.g. if you want to declare public var, just name it Pressed. Or private - (Unity) m_Pressed, C# default (_pressed)

 

Is there some documentation on why a variable can't be started with a digit?

 

Here is the official Microsoft spec- whizz down to the heading "Identifiers".

 

I think, it is a programming principle, not to give names, starting with numbers.
The reason would probably be heading back to early ages of programming, when certain limitation where implied, to ensure system works. For example short naming convention. This days, generally that is not a problem, yet not necessary you can have infinite path, or variable. But they can be pretty long.

Regarding your variable, you can rename it to
is3Dpressed, or is3D_pressed, or is_3D_pressed
first one is nice and clean.

I tend use (is) prefix for Boolean, or (b_), if (is) not suitable.
With constant prefixes, it is easier to find relevant type of variables, when many of them are in the scope.

 

Ok thanks for your suggestions. I personally end the name of each Boolean with _bo.

 

In fact out of interest, I use prefixes for most of variables.
I.e.
is or b_ -> Boolean
i_ -> integer
f_ -> float
d_ -> double
s_ -> string
V3_ -> Vector3
l_ -> list
dic_ -> dictionary
and got few more

So for example I can have:

Code (CSharp):

1.  
2. float f_velocity = 10.5f ;
3. Vector3  V3_velocity = Vector.forward * f_velocity ;
4. List <Vector3> l_velocity = new List <Vector3> () ; // I never use var
5. l_velocity.Add ( V3_velocity ) // list of velocities
6.  

So as you can see, I can use same name base, for different variables.

 

Personal taste, I'd be totally annoyed by all these type-indicating prefixes.

One thing I use as well are prefixes such as 'Is' ('Has' and you can sometimes even find 'Can' in the .Net framework). They can be used to avoid confusion between boolean members and events, as the latter often use a present and past tense (at least that is a common convention).

 

Cool insight. I tend to add mine at the end. For example - pseudo code
3D_pressed_bo - Boolean variable
child_object_cube_tfm - I use _tfm for Transform variables. Do you have a prefix for Transform variables.

 

yep
Tr_ -> Transform
Rb_ -> Rigidbody
Q_ -> Quaternion

But in general, I try to avoid underscore in names.
I use them Only, if I separate category of variable type. Rarely, since then using classes instead, to group variables.
But in case naming with multiple words, I capitalist first letter of each word, other than first word after prefix, I could write:
Tr_guyRunningThroughForest
V3_myCarVelocity
Q_homeOnTheMoon -> since is quaternion, I don't specify that this is rotation

then classes are starting with capital always
class Car {}
class CarGarage {}

while methods use additionally underscore and also first capital letter
void _GetCarPosition () {}
void _AddCar2Garage () {}-> I use 2 as To, or 4 as For (for me much better than _AddCarToGarage, or _Add_Car_To_Garage)
void _GetSpeed () {} ;

etc ..

And if I got class for example

Code (CSharp):

1. class SpaceCraft
2. {
3.     string s_name ;
4.  
5.     Transform Tr ; // it is abvious, it belongs to SpaceCraft, so no extra naming in variable
6.     Rigidbody Rb ; // same here
7.  
8. }

 

I know is from person to person preference.
I took concept and adapted prefixes naming, from when I was programming PLCs.
Serves me well

Also, rarely the case, but if happens that I am viewing the code from none C# (or relevant language) formatted editor, prefixes becomes helpful.

In case I see
car.acceleration = Vector2.right ;
I will not know straight forward, that car acceleration is a Vector3; Yes, I can hover over variable etc.
Also
car.happiness = 3 ; // but because I haven't put (f) after number, is not obvious, that this value can take float and be
car.happiness = 2.5f ;

Now you have bunch of these in method and you will be checking each variable, which is int, double, or maybe float.
Hence in my case, prefixes are very useful.

 

Yes, it is indeed personal preference, a very special one though.

The thing is, you wouldn't encode type information in method names, would you? Instead, you'd simply take a look at the signature and its parameter list to actually check your options.

In the end, we're dealing with a strongly typed language, which renders a lot of prefixes and suffixes redundant.