041 what’s happening: calling a method

When the computer runs your program, it reads one line of code at a time. It moves words and numbers around in its memory. It is like moving sticky notes around on your desk.

Here is what one of the wheel lines you wrote in L040 does.

hardware.frontLeft.setPower(leftSpeed);
../_images/fig-l040-sticky.png

  • The computer finds the variable hardware, and the big blue note its arrow points to.

  • On that note is the field frontLeft. Its arrow points to a motor’s note.

  • A motor has a method, setPower, and the line hands it leftSpeed. That is the double on leftSpeed’s note, 0.7 in the picture.

  • setPower is part of the FTC platform. It runs that motor full power forward at +1.0, not at all at 0.0, and full power backward at -1.0.

  • The same happens for each of the four: frontLeft, backLeft, frontRight and backRight.