flatmap

I have a list of animals: let animals = ["bear", "dog", "cat"] And some ways to transform that list: typealias Transform = (String) -> [String] let containsA: Transform = { $0.contains("a") ? [$0] : [] } let plural: Transform = { [$0 + "s"] } let double: Transform = { [$0, $0] } As a slight aside, these are analogous to filter (outputs 0 or 1 element), map (exactly 1 element) and flatmap (more than 1 element) respectively but defined in a uniform way so that they can be handled consistently. I want to create a lazy iterator which applies an array of these transforms to the list of animals:

I'm a little confused around flatMap (added to Swift 1.2) Say I have an array of some optional type e.g. let possibles:[Int?] = [nil, 1, 2, 3, nil, nil, 4, 5] In Swift 1.1 I'd do a filter followed by a map like this: let filtermap = possibles.filter({ return $0 != nil }).map({ return $0! }) // filtermap = [1, 2, 3, 4, 5] I've been trying to do this using flatMap a couple ways: var flatmap1 = possibles.flatMap({ return $0 == nil ? [] : [$0!] }) and var flatmap2:[Int] = possibles.flatMap({ if let exercise = $0 { return [exercise] } return [] }) I prefer the last approach (because I don't have to

We have an array of the Person objects and each object has another array of String, which is optional. We want the consolidated list of car names in our society. struct Person { let name: String let address: String let age: Int let income: Double let cars: [String]? } let personsArray = [Person(name:"Santosh", address: "Pune, India", age:34, income: 100000.0, cars:["i20","Swift VXI"]), Person(name: "John", address:"New York, US", age: 23, income: 150000.0, cars:["Crita", "Swift VXI"]), Person(name:"Amit", address:"Nagpure, India", age:17, income: 200000.0, cars:nil)] let flatmapArray =

I'm having a problem with the following code. I'm downloading a list of actors in JSON and I want to populate Struct Actor with the received data. Everything works great until I try to flatMap on the received data and try to initialize the struct Actor. When I try to compile the code i get the error: Cannot assign value of type '()' to type [Actor]. The error corresponds to a line in viewDidLoad actorsList = downloadActors() Would anybody have any recommendation who to solve this? import UIKit func downloadActors() { var request = URLRequest(url: URL(string: "url...")!) request.httpMethod =

I'm trying to use flatmap to make a nested loop with the Stream API, but I can't seem to figure it out. As an example, I want to recreate the following loop: List<String> xs = Arrays.asList(new String[]{ "one","two", "three"}); List<String> ys = Arrays.asList(new String[]{"four", "five"}); System.out.println("*** Nested Loop ***"); for (String x : xs) for (String y : ys) System.out.println(x + " + " + y); I can do it like this, but this seems ugly: System.out.println("*** Nested Stream ***"); xs.stream().forEach(x -> ys.stream().forEach(y -> System.out.println(x + " + " + y)) ); Flatmap looks

I was examining .lazy for high order functions and have got some interesting compile errors related to flatMap function (and possibly others) Examples let array = [1, 2, 3, 4, 5, 6] array .flatMap { print("DD") return $0 // Cannot convert return expression of type 'Int' to return type 'String?' } .forEach { print("SS") print($0) } Commenting out a bit array .flatMap { // print("DD") return $0 } .forEach { print("SS") print($0) } And everything works.. even more interesting example array .flatMap { let z = $0 return $0 // Or return z - all is the same "Cannot convert return expression of type