filtersExample.swift

// Hold the filter and the closure that updates its value
var filtersAndValueUpdaters: [ (Filter, ((Float, Int) -> Void)) ] = []

// The selected filter has also the closure that updates its value
var selectedfilter: (Filter, (Float, Int) -> Void)

let filterA = FilterA()
filtersAndValueUpdaters.append((filterA, { [weak filterA] value, _ in
   filterA?.param = value
}))