Checking if an array of custom objects contain a specific custom object

Question

say i have a very simple Person class

class Person {     var name:String     init(name:String) {         self.name = name     } } 

and i wish to store a collections of such Persons in a property, which is an array with type Person, of a People class

class People {     var list:[Person] = [] } 

perhaps i achieve this as follows

var alex = Person(name:"Alex") var people = People() people.list.append(alex) 

QUESTION: how do i check if people.list contains the instance alex, please?

my simple attempt, which i was hoping to return true

people.list.contains(alex) 

calls an error "cannot convert value of type 'Person' to expected argument type '@noescape (Person) throws -> Bool'"

Answer 1

There are two contains functions:

extension SequenceType where Generator.Element : Equatable {     /// Return `true` iff `element` is in `self`.     @warn_unused_result     public func contains(element: Self.Generator.Element) -> Bool }  extension SequenceType {     /// Return `true` iff an element in `self` satisfies `predicate`.     @warn_unused_result     public func contains(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Bool } 

The compiler is complaining because the compiler knows that Person is not Equatable and thus contains needs to have a predicate but alex is not a predicate.

If the people in your array are Equatable (they aren't) then you could use:

person.list.contains(alex) 

Since they aren't equatable, you could use the second contains function with:

person.list.contains { $0.name == alex.name } 

or, as Martin R points out, based on 'identity' with:

person.list.contains { $0 === alex } 

or you could make Person be Equatable (based on either name or identity).

Answer 2

QUESTION: how do i check if people.list contains the instance alex, please?

class Person is a reference type, and var alex is a reference to the object storage. The identical-to operator === checks if two constants or variables refer to the same instance of a class.

Therefore, in order to check if the list contains a specific instance, use the predicate-based contains() method, and compare instances with ===:

if people.list.contains({ $0 === alex }) {     // ... }