p5 lib static + instance dual implementation ?

lauriej1316

Hiya,

This isn't technically a 'using p5' question, but I'm getting into writing my own client side js libraries and I wanted to see how p5 used both static and instance versions of functions such as p5.Vector.sub() ... so take a look here:

https://github.com/processing/p5.js/blob/master/src/math/p5.Vector.js#L269

I'm guessing lines 282-284 are the static version, but why does the function reference the x, y, z that belong to 'this' before returning it ? Aren't those instance variables ? It also performs -= on them, so surely if you use the static version more than once, won't it be affected by all the previous times you used it ?

Many thanks for any pointers.

Thx, Loz

GoToLoop

• On that link you've posted, method sub() is a member of the constructor's prototype{} object:
  https://GitHub.com/processing/p5.js/blob/master/src/math/p5.Vector.js#L269-L286
• Therefore, that's the non-static version, whose this points to the current p5.Vector instance which had invoked it.
• Its corresponding static version is here instead:
  https://GitHub.com/processing/p5.js/blob/master/src/math/p5.Vector.js#L1080-L1088
• This time, method sub() is a direct property/member of the p5.Vector constructor/class.
• It doesn't access this either. Instead it uses any passed p5.Vector parameters.

GoToLoop

If you wish, you may also take a look at Pjs' own implementation of class PVector:
https://Gist.GitHub.com/GoToLoop/acbf106aa784820aff23

It's much closer to Processing Java's PVector class than p5.js is. ~O)

lauriej1316

as usual, you nailed it matey :):)

totally missed that it has functions both on and not on the prototype.

thx !