How to remove elements from array that match elements in another array?
Assume we have an array and we loop through it and find out which elements to remove:
var sourceItems = [ ... ]
var removedItems = [SKShapeNode]()
for item : SKShapeNode in sourceItems {
if item.position.y > self.size.height {
removedItems.append(item)
item.removeFromParent()
}
}
sourceItems -= removedItems // well that won't work.
You can use the filter function.
let a = [1, 2, 3]
let b = [2, 3, 4]
let result = a.filter { element in
return !b.contains(element)
}
result will be [1]
Or more succinctly...
let result = a.filter { !b.contains($0) }
Check out the Swift Standard Library Reference
Or you can use the Set type.
let c = Set<Int>([1, 2, 3])
let d = Set<Int>([2, 3, 4])
c.subtract(d)
NSMutableArray has a filter method that does just that however.
!contains(b, element). Now in Swift 2.x we use !b.contains(element)Be mindful if using the Set option, that your results only be unique values and will not maintain the initial ordering, if that matters to you, whereas the Array filter option will maintain the initial array's order, at least what elements remain.
Swift 3
let c = Set<Int>([65, 1, 2, 3, 1, 3, 4, 3, 2, 55, 43])
let d = Set<Int>([2, 3, 4])
c.subtracting(d)
c = {65, 2, 55, 4, 43, 3, 1}
d = {2, 3, 4}
result = {65, 55, 43, 1}