I have a Person() class:
class Person : NSObject {
var firstName : String
var lastName : String
var imageFor : UIImage?
var isManager : Bool?
init (firstName : String, lastName: String, isManager : Bool) {
self.firstName = firstName
self.lastName = lastName
self.isManager = isManager
}
}
I have an array of Person()
var peopleArray = [Person]()
I want to count the number of people in the array who have
isManager: true
I feel this is out there, but I can;t find it, or find the search parameters.
Thanks.
Use filter
method:
let managersCount = peopleArray.filter { (person : Person) -> Bool in
return person.isManager!
}.count
or even simpler:
let moreCount = peopleArray.filter{ $0.isManager! }.count
You can use reduce
as follows:
let count = peopleArray.reduce(0, combine: { (count: Int, instance: Person) -> Int in
return count + (instance.isManager! ? 1 : 0) }
)
or a more compact version:
let count = peopleArray.reduce(0) { $0 + ($1.isManager! ? 1 : 0) }
reduce
applies the closure (2nd parameter) to each element of the array, passing the value obtained for the previous element (or the initial value, which is the 0
value passed as its first parameter) and the current array element. In the closure you return count
plus zero or one, depending on whether the isManager property is true
or not.
More info about reduce
and filter
in the standard library reference
count(where:)
was removed from Swift 5 in Xcode 10.2 beta 4.
With Swift 5 and Xcode 10.2 beta 3, you can use Array
's count(where:)
method if you want to count the number of elements in an array that match a given predicate. count(where:)
has the following declaration:
func count(where predicate: (Element) throws -> Bool) rethrows -> Int
Returns the number of elements in the sequence that satisfy the given predicate.
The following Playground sample code shows how to use count(where:)
:
struct Person {
let name: String
let isManager: Bool
}
let array = [
Person(name: "Jane", isManager: true),
Person(name: "Bob", isManager: false),
Person(name: "Joe", isManager: true),
Person(name: "Jill", isManager: true),
Person(name: "Ted", isManager: false)
]
let managerCount = array.count(where: { (person: Person) -> Bool in
return person.isManager == true
})
// let managerCount = array.count { $0.isManager } // also works
print(managerCount) // prints: 3
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.