Swift 2.0 filtering array of custom objects - Cannot invoke 'filter' with an argument of list type

Question

trying to filter an array of custom object type ParseEmployee which inherits from NSObject.

Any ideas what could be causing this error?

Answer 1

Consider the following example:

struct MyEmployee {
    var employeeId : Int
    var employeeName : String
    var employeeAge : Int
    var employeeGender : String

    init(_ id: Int, _ name: String, _ age: Int, _ gender: String) {
        employeeId = id
        employeeName = name
        employeeAge = age
        employeeGender = gender
    }
}

var arrayOfEmployees : [MyEmployee] = [MyEmployee(1, "John", 28, "Male"), MyEmployee(2, "Sarah", 35, "Female"), MyEmployee(3, "Christine", 24, "Female")]

var filtered = arrayOfEmployees.filter {employee in employee.employeeAge < 30 }
print(filtered) // Employee objects John and Christine

The closure following .filter suffix to your array must be of return type Bool ("element-type-of-array" -> Bool). You either explicitly add a return or simply make sure the statement following employee in is one that evaluates to type Bool (e.g., employee.employeeAge < 30, which returns true or false).

Note that you can treat the closure as any anonymous closure type, not necessarily using a single-line statement. E.g.:

var anotherFiltered = arrayOfEmployees.filter{
    employee in
    return employee.employeeAge < 30 && employee.employeeGender == "Female" }
print(anotherFiltered) // Employee object Christine

Answer 2

You should be able to run as the following:

filtered = arrayOfEmployees.filter { // filter them here }

$0 will be the member of the array and you just have to make sure the braces return a true or false Bool, you do not need to do (employee) -> Bool in here.

If you wanted employee just do the following:

filtered = arrayOfEmployees.filter { employee in // filter here }

Answer 3

Your filter closure has to return a Bool.

So something like.

filtered = arrayOfEmployees.filter { return true }

Now that's not useful because nothing is filtered but it fixes your error. Let's say your ParseEmployee has a property isManager:Bool. Then you could do something like.

filtered = arrayOfEmployees.filter { $0.isManager }

Answer 4

My problem was that I had copied and pasted the "filtered" array from another class and didn't change it to the appropriate class type that was being filtered. I changed the filtered array to the correct class and this resolved the error.