How to keep calling a function till it returns a different output than before? [duplicate] - xcode

Question

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Randomly choosing an item from a Swift array without repeating
(6 answers)
Closed 6 years ago.
I have a function that will randomly output a SKColor.
func getRandomColor() -> SKColor{
let randomaval = arc4random_uniform(4)
var color = SKColor()
switch(randomaval)
{
case 0:
color = redColor
case 1:
color = greenColor
case 2:
color = blueColor
case 3:
color = yellowColor
default:()
}
return color
}
When two bodies collide I call this function to change colors
aball.color = getRandomColor()
if aball.color == redColor && getRandomColor() == redColor {
aball.color = getRandomColor() //to set the color to something other than red
aball.colorBlendFactor = 1.0
}
What I want to do is that, when I say aball.color = getRandomColor(), if getRandomColor() is redColor again, it needs to run the if statement again till the function returns something other than redColor. Most of the time, when my if condition is true, it calls redColor again and I can't understand how to avoid that. I basically want a different color to be returned everytime getRandomColor is called. How do I accomplish that?

Answer 1

How about repeatedly calling your getRandomColor() function until the result is something other than the ball's current color? :
repeat {
let newColor = getRandomColor()
} while newcolor != aball.color
aball.color = newColor
Alternatively, you could re-write getRandomColor to accept a parameter of a color it shouldn't return and then call your amended function with aball.color:
func getRandomNumber(notColor: SKColor) -> SKColor{
repeat {
let randomaval = arc4random_uniform(4)
var color = SKColor()
switch(randomaval)
{
case 0:
color = redColor
case 1:
color = greenColor
case 2:
color = blueColor
case 3:
color = yellowColor
default:()
}
let newColor = getRandomColor()
} while color != notColor
return color
}
Then, when you want to change the color of the ball:
aball.color = getRandomColor(notColor: aball.color)
another approach is to have getRandomColor track its own last result. In your initialisation decalre:
var lastrandomcolor: SKColor
then
func getRandomNumber() -> SKColor{
repeat {
let randomaval = arc4random_uniform(4)
var color = SKColor()
switch(randomaval)
{
case 0:
color = redColor
case 1:
color = greenColor
case 2:
color = blueColor
case 3:
color = yellowColor
default:()
}
let newColor = getRandomColor()
} while color != lastRandomColor
lastRandomcolor = color
return color
}
then just use:
aball.color = getRandomColor()
I prefer the 2nd approach where your pass a color that you don't want returned, as it gives you more control i.e. at certain times, you might not want the ball to be some other colour, not just it's own color. e.g. not blue if its in the sky. you could even pass an array of colours that shouldn't be returned.