Does Swift have a short circuit to higher-order functions such as Any or All?

Question

I know about higher order quick functions like Map, Filter, Reduce and FlatMap, but I don't know anyone like “All” or “Any” that return a boolean that short circuit on a positive test listing the results.

For example, consider that you have a collection of 10,000 objects, each of which has a property with a name isFulfilled, and you want to see if this collection is set isFulfilledto false. In C #, you could use myObjects.Any(obj -> !obj.isFulfilled), and when this condition was removed, it shorted the rest of the enumeration and returned immediately true.

Is there such a thing in Swift?

Answer 1

Sequence(and in particular Collectionand Array) has a (short-circuited) contains(where:)method that takes boolean predicate as an argument. For instance,

if array.contains(where: { $0 % 2 == 0 })

checks if the array contains any even number.

There is no “all” method, but you can use contains()as well as denying both the predicate and the result. For instance,

if !array.contains(where: { $0 % 2 != 0 })

checks if all numbers in the array are even. Of course, you can define your own extension method:

extension Sequence {
    func allSatisfy(_ predicate: (Iterator.Element) -> Bool) -> Bool {
        return !contains(where: { !predicate($0) } )
    }
}

If you want to allow predicate throwing in the same way as contains, then it will be defined as

extension Sequence {
    func allSatisfy(_ predicate: (Iterator.Element) throws -> Bool) rethrows -> Bool {
        return try !contains(where: { try !predicate($0) } )
    }
}

Answer 2

, Swift, " " , lazy , - :

myObjects.lazy.filter({ !$0.isFulfilled }).first != nil

, , . lazy Apple. :

var lazy: LazyCollection > , .

var lazy: LazySequence > , , , , .

Answer 3

, , isFulfilled..., , confrom ( fullFilled)... [FulfilledItem]... , ,

:

, Any AnyObject, AnyObject ( Apple, ), " " - AnyObject...

 protocol FulfilledItem: AnyObject{

    var isFulfilled: Bool {get set}

}

class itemWithTrueValue: FulfilledItem{
    var isFulfilled: Bool = true
}

class itemWithFalseValue: FulfilledItem{
    var isFulfilled: Bool = false
}

var arrayOfFulFilled: [FulfilledItem] = [itemWithFalseValue(),itemWithFalseValue(),itemWithFalseValue(),itemWithFalseValue(),itemWithFalseValue(),itemWithFalseValue()]

  let boolValue =   arrayOfFulFilled.contains(where: {
       $0.isFulfilled == false
    })

, Any + isFulfilled , , ...

:

https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/TypeCasting.html#//apple_ref/doc/uid/TP40014097-CH22-ID342

AnyObject (), Any - , , , AnyObject...

AnyObject Array Item FulfilledItem, ( , ...)

:)