Swift tip: Initialization of variable is never used consider replacing with assignment to _ or removing it

var//represents variable, variable value can be changed

let//represents a constant type that cannot be changed

var ceshi:Double = 10//If the declared variable is not changed, Swift will also prompt to change it to let, and the variable in the following code is not used in Swift will prompt to change to underline, Because the underscore means ignoring the variable, which is equivalent to the hint in OC is not the same as the attribute or variable, the estimated useless variables are not written by the General people, just to get started to say that you did not write the wrong or Xcode has a problem, but swift hints very fine. You can assign a new value to Ceshi directly below, in print.

Swift tip: Initialization of variable is never used consider replacing with assignment to _ or removing it