Count number of items in an array with a specific property value

Question

I have a Person() class:

class Person : NSObject {

    var firstName : String
    var lastName : String
    var imageFor : UIImage?
    var isManager : Bool?

          


        

Answer 1

count(where:) was removed from Swift 5 in Xcode 10.2 beta 4.

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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.

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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
})
// let managerCount = array.count { $0.isManager } // also works
        
print(managerCount) // prints: 3