I have an array of MyObject where my object is like this:
class MyObject: Equatable {
var name: String?
var age: Int?
init(name: String, age: Int) {
self.name = name
self.age = age
}
}
func ==(first: MyObject, second: MyObject) -> Bool {
return first.name == second.name
}
Let's say my array is:
var array: [MyObject]
Is there a way to use find(sequence, element) function like this? :
var myFoundObject = find(array, "name_of_the_object_I_m_looking_for")
Thanks for your help.
As #Kirsteins mentioned, find returns the index.
You can easily implement your own find which accept testing function, like filter:
func find<C:CollectionType, U where C.Generator.Element == U>(domain:C, isValue:U -> Bool) -> C.Index? {
for idx in indices(domain) {
if isValue(domain[idx]) {
return idx
}
}
return nil
}
// usage
let array = ["foo", "bar", "baz"]
if let found = find(array, { $0.hasSuffix("az") }) {
let obj = array[found]
}
Using this, you can:
if let found = find(array, { $0.name == "name_of_the_object_I_m_looking_for" }) {
let myFoundObject = array[found]
}
find function returns the index of object in collection, not the object.
You have to iterate ovre array to find the object that matches you criteria, for example:
var myObject: MyObject? = {
for object in array {
if "name_of_the_object_I_m_looking_for" == object.name {
return object
}
}
return nil
}()
Related
I have written the following extension for Collection in Swift that returns a new Collection of every other element from a starting index.
extension Collection {
func everyOtherElement(from theIndex: Int = 0) -> [Element] {
if theIndex >= self.count { return self as! [Element] }
let start = self.index(startIndex, offsetBy: theIndex)
let end = self.endIndex
var everyOther = [Element]()
var iter = start
while iter != end {
everyOther.append(self[iter])
let next = index(after: iter)
if next == end { break }
iter = index(after: next)
}
return everyOther
}
}
There are probably ways to improve the code but my issue is when the Collection is a Dictionary. The extension works but returns an Array of Tuples [(key: key, value: value)]
I would like the extension to return a Dictionary.
I have tried Dictionary(uniqueKeysWithValuesMethod) which works fine once applied to the return of the everyOtherElement method but I can't seem to find a way to make it so directly.
var myDictionary = ["EN" : "Cheers", "SV" : "Skåll", "ES" : "Salud" ].everyOtherElement()
// returns [(key: "EN", value: "Cheers"),(key: "ES", value: "Salud")]
Dictionary(uniqueKeysWithValues: myDictionary.map { ($0.key, $0.value)})
// returns ["EN" : "Cheers", "ES" : "Salud" ]
Thanks for your help!
As other have mentioned a Dictionary is an unordered collection. If you would like to return a Dictionary you can simply extend dictionary and filter every other element. Note that there is no guarantee that the dictionary will keep the order that the key value pairs were enterer. That being said you can accomplish what you want as follow:
extension Dictionary {
var everyOtherElements: Dictionary {
var bool = true
return filter { _ in
defer { bool = !bool }
return bool
}
}
}
let dict = ["EN" : "Cheers", "SV" : "Skåll", "ES" : "Salud" ]
// returns [(key: "EN",
let everyOtherElements = dict.everyOtherElements // ["ES": "Salud", "SV": "Skåll"]
Regarding your comment
I understand from your reply that I can't extend all collection with
the same code, I need to break it down per type?
You don't need to extend every single element type, you can for instance extend RangeReplaceableCollection protocol and return Self which will englobe Strings as well:
extension RangeReplaceableCollection {
mutating func removeEvenIndexElements() {
var bool = true
removeAll { _ in
defer { bool = !bool }
return bool
}
}
mutating func removeOddIndexElements() {
var bool = false
removeAll { _ in
defer { bool = !bool }
return bool
}
}
func evenIndexElements() -> Self {
var bool = true
return filter { _ in
defer { bool = !bool }
return bool
}
}
func oddIndexElements() -> Self {
var bool = false
return filter { _ in
defer { bool = !bool }
return bool
}
}
}
var alphabet = "abcdefghijklmnopqrstuvwxyz"
alphabet.removeEvenIndexElements()
alphabet // "bdfhjlnprtvxz"
var arr = [1,2,3,4,5,6,7,8,9,0]
arr.removeOddIndexElements()
arr // [1, 3, 5, 7, 9]
I'm working on a project in Swift 3 where I have a tuple array with duplicate values is there a way to save it to a NSSet or to avoid replicating the same value. The structure of my tuple array as follow.
var selectedSongList : [(title: String, healerName: String, trackUrl: String, trackID: String, imageUrl: String)] = []
Thus later I'm using this to poplate my UITableView
There are two ways to do it.
Solution 1
You can create a structure and it should confirm to Hashable and equatable some thing like this
struct Post: Hashable, Equatable {
let id: String
var hashValue: Int { get { return id.hashValue } }
}
func ==(left:Post, right:Post) -> Bool {
return left.id == right.id
}
and to remove your object you can do like this
let uniquePosts = Array(Set(posts))
Solution 2
Create a set out of your array and then make it back to array.
Edit func static func == in Song struct if you have different definition about the same song
struct Song: Equatable {
var title: String?
var healerName: String?
var trackUrl:String?
var trackID:String?
var imageUrl: String?
init(_ title: String, _ healerName:String, _ trackUrl:String, _ trackID:String,_ imageUrl: String) {
self.title = title
self.healerName = healerName
self.trackUrl = trackUrl
self.trackID = trackID
self.imageUrl = imageUrl
}
static func == (lhs: Song, rhs: Song) -> Bool {
return lhs.title == rhs.title &&
lhs.healerName == rhs.healerName &&
lhs.trackUrl == rhs.trackUrl &&
lhs.trackID == rhs.trackID &&
lhs.imageUrl == rhs.imageUrl
}
}
extension Array where Element:Equatable {
func removeDuplicates() -> [Element] {
var result = [Element]()
for value in self {
if result.contains(value) == false {
result.append(value)
}
}
return result
}
}
I've been playing around with Generics and Extensions to existing types in Swift 3. I wrote two generic Array functions that extends Array with find-and-replace methods, named replaced() and replace(). The replaced() function works as intended but the replace() function has a compile time error. Here is the code and a test of one of the methods.
extension Array {
func replaced<T: Equatable>(each valueToReplace: T, with newValue: T) -> [T] {
var newArray:[T] = []
for index:Int in 0..<self.count {
if let temp = self[index] as? T, temp == valueToReplace{
newArray.append(newValue)
}else{
newArray.append(self[index] as! T)
}
}
return newArray
}
mutating func replace<T: Equatable>(each valueToReplace: T, with newValue: T) {
for index:Int in 0..<self.count {
if let temp = self[index] as? T, temp == valueToReplace {
// FIXME: self[index] = newValue
}
}
return
}
}
var j = [1,2,3,4,3,6,3,8,9]
var newArray = j.replaced(each: 3, with: 0)
I get a compile time error on the second method, replace(), at the line commented out with "//FIXME:" annotation. The compile time error says, "Ambiguous reference to member 'subscript'".
How can I fix the replace() code so it works?
Give this a shot
extension Array where Element: Equatable {
func replaced (each valueToReplace: Element, with newValue: Element) -> [Element] {
var newArray = [Element]()
newArray.reserveCapacity(self.count)
for element in self {
let newElement = (element == valueToReplace) ? newValue : element
newArray.append(newElement)
}
return newArray
}
mutating func replace(each valueToReplace: Element, with newValue: Element) {
for (i, element) in self.enumerated() {
if element == valueToReplace { self[i] = newValue }
}
}
}
var j = [1,2,3,4,3,6,3,8,9]
var newArray = j.replaced(each: 3, with: 0)
It would be better to remove the redundancy by just making replaced delegate to replace:
extension Array where Element: Equatable {
func replaced(each valueToReplace: Element, with newValue: Element) -> [Element] {
var copy = self
copy.replace(each: valueToReplace, with: newValue)
return copy
}
mutating func replace(each valueToReplace: Element, with newValue: Element) {
for (i, element) in self.enumerated() {
if element == valueToReplace { self[i] = newValue }
}
}
}
Let say I have following code
class Foo {
}
var fooArray : Array<Foo> = Array<Foo>()
// This is important because in my code I will get Any (vs Array<Foo)
var fooArrayAny : Any = foo
I want to be able to get a Type Foo out of variable fooArrayAny.
If I had fooArray, I would do something like that:
let type = fooArray.dynamicType.Element().dynamicType
However, this doesn't work with fooArrayAny. It says that it has no member Element()
If you set NSObject as the base class of Foo, then you could use the following code:
class EVReflectionTests: XCTestCase {
func testArrayInstance() {
let fooArray : Array<Foo> = Array<Foo>()
let fooArrayAny : Any = fooArray
if let arr = fooArray as? Array {
let i = arr.getArrayTypeInstance(arr)
print("i = \(i)")
}
}
}
class Foo: NSObject {
}
extension Array {
public func getArrayTypeInstance<T>(arr:Array<T>) -> T {
return arr.getTypeInstance()
}
public func getTypeInstance<T>() -> T {
let nsobjectype : NSObject.Type = T.self as! NSObject.Type
let nsobject: NSObject = nsobjectype.init()
return nsobject as! T
}
}
This code is a snippet of my library EVReflection
Update:
I noticed a mistake in the code above. I used fooArray instead of fooArrayAny. When changing that to fooArrayAny I get the same error as you that the compiler does not have the Element. After playing around with this, I found out a solution that does work. Again it has parts of code of my EVReflection library.
class EVReflectionTests: XCTestCase {
func testArrayInstance() {
let fooArray : Array<Foo> = Array<Foo>()
let fooArrayAny : Any = fooArray
if let _ = fooArrayAny as? NSArray {
var subtype: String = "\(Mirror(reflecting: fooArrayAny))"
subtype = subtype.substringFromIndex((subtype.componentsSeparatedByString("<") [0] + "<").endIndex)
subtype = subtype.substringToIndex(subtype.endIndex.predecessor())
print("The type of the array elements = \(subtype)")
if let instance = swiftClassFromString(subtype) {
print("An instance of the array element = \(instance)")
let type = instance.dynamicType
print("An instance of the array element = \(type)")
}
}
}
// All code below is a copy from the EVReflection library.
func swiftClassFromString(className: String) -> NSObject? {
var result: NSObject? = nil
if className == "NSObject" {
return NSObject()
}
if let anyobjectype : AnyObject.Type = swiftClassTypeFromString(className) {
if let nsobjectype : NSObject.Type = anyobjectype as? NSObject.Type {
let nsobject: NSObject = nsobjectype.init()
result = nsobject
}
}
return result
}
func swiftClassTypeFromString(className: String) -> AnyClass! {
if className.hasPrefix("_Tt") {
return NSClassFromString(className)
}
var classStringName = className
if className.rangeOfString(".", options: NSStringCompareOptions.CaseInsensitiveSearch) == nil {
let appName = getCleanAppName()
classStringName = "\(appName).\(className)"
}
return NSClassFromString(classStringName)
}
func getCleanAppName(forObject: NSObject? = nil)-> String {
var bundle = NSBundle.mainBundle()
if forObject != nil {
bundle = NSBundle(forClass: forObject!.dynamicType)
}
var appName = bundle.infoDictionary?["CFBundleName"] as? String ?? ""
if appName == "" {
if bundle.bundleIdentifier == nil {
bundle = NSBundle(forClass: EVReflection().dynamicType)
}
appName = (bundle.bundleIdentifier!).characters.split(isSeparator: {$0 == "."}).map({ String($0) }).last ?? ""
}
let cleanAppName = appName
.stringByReplacingOccurrencesOfString(" ", withString: "_", options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil)
.stringByReplacingOccurrencesOfString("-", withString: "_", options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil)
return cleanAppName
}
}
class Foo: NSObject {
}
The output of this code will be:
The type of the array elements = Foo
An instance of the array element = <EVReflection_iOS_Tests.Foo: 0x7fd6c20173d0>
An instance of the array element = Foo
Swift 5
Its old but I want to share my version if someone needs it.
I use ModelProtocol and I suggests you use protocol so we can do operation to model via protocol (ex: static instantiating).
protocol ModelProtocol {}
class Foo: ModelProtocol {
}
Since I can't check type is Array, I use CollectionProtocol and create Array extension to get Element via protocol.
protocol CollectionProtocol {
static func getElement() -> Any.Type
}
extension Array: CollectionProtocol {
static func getElement() -> Any.Type {
return Element.self
}
}
Testing.
var fooArray: Array<Foo> = Array<Foo>()
var fooArrayAny: Any = fooArray
let arrayMirrorType = type(of: fooArrayAny)
String(describing: "arrayMirrorType: \(arrayMirrorType)")
if arrayMirrorType is CollectionProtocol.Type {
let collectionType = arrayMirrorType as! CollectionProtocol.Type
String(describing: "collectionType: \(collectionType)")
let elementType = collectionType.getElement()
String(describing: "elementType: \(elementType)")
let modelType = elementType as! ModelProtocol.Type
String(describing: "modelType: \(modelType)")
// ... now you can do operation to modelType via ModelProtocol
}
Printing.
arrayMirrorType: Array<Foo>
collectionType: Array<Foo>
elementType: Foo
modelType: Foo
class Foo {
var foo: Int = 1
}
struct Boo {
var boo: String = "alfa"
}
func f(array: Any) {
let mirror = Mirror(reflecting: array)
let arraytype = mirror.subjectType
switch arraytype {
case is Array<Foo>.Type:
let fooArray = array as! Array<Foo>
print(fooArray)
case is Array<Boo>.Type:
let booArray = array as! Array<Boo>
print(booArray)
default:
print("array is not Array<Foo> nor Array<Boo>")
break
}
}
var fooArray : Array<Foo> = []
fooArray.append(Foo())
var anyArray : Any = fooArray // cast as Any
f(anyArray) // [Foo]
var booArray : Array<Boo> = []
booArray.append(Boo())
anyArray = booArray // cast as Any
f(anyArray) // [Boo(boo: "alfa")]
var intArray : Array<Int> = []
anyArray = intArray // cast as Any
f(anyArray) // array is not Array<Foo> nor Array<Boo>
I want to iterate over an array of arrays so search for a specific item and return true if exits.
var fruits = ["apple", "banana"]
var names = ["ivan", "john", "maria"]
var mainArray = [fruits, names]
// i want to return true if theres a name/fruit that is "john"
func search() -> Bool {
for object in mainArray {
if (object.filter { $0 == "john" }).count > 0 {
return true
}
}
return false
}
search()
This works but there a shorter version using .map and avoiding for object in mainArray ?
like mainArray.map.filter... ?
var fruits = ["apple", "banana"]
var names = ["ivan", "john", "maria"]
var mainArray = [fruits, names]
func search() -> Bool {
return mainArray.contains { $0.contains("john") }
}
Or, in Swift 1:
func search() -> Bool {
return contains(mainArray) {
inner in contains(inner) {
$0 == "john"
}
}
}
As was pointed out by #AirspeedVelocity, you can actually make those closures have shorthand arguments:
func search() -> Bool {
return contains(mainArray) { contains($0) { $0 == "john" } }
}
I know this doesn't use map and filter, but why don't you use contains ?
func search() -> Bool {
for object in mainArray {
if contains(object, "john") {
return true
}
}
return false
}