“Expression is not assignable” — Problem assigning float as sum of two other floats in Xcode?

Question

In a piano app, I\'m assigning the coordinates of the black keys. Here is the line of code causing the error.

\'blackKey\' and \'whiteKey\' are both customViews

Answer 1

As its meanings, you can't assign value to expression. For instance, a + b = c it is forbidden.