EDIT:
I would like to delete one of the element in the array list of structure type
struct Folder {
let name:String
let menu:[String:String]
}
I have a variable of
section = Folder
I want to check that is there any value in menu[String:String] contain specific value or not and remove that element out
section.menu = ["hello" : "a","b","c"]
if there any value of hello == a {
remove it out
}
At the end
section.menu = ["hello" : "b","c"]
You can create mutating function like that removeMenu(forValue value: String)
struct Folder {
let name:String
var menu:[String:String]
mutating func removeMenu(forValue value: String) {
menu = menu.filter({ $0.value != value})
}
}
var section = Folder(name: "FolderName", menu: ["k1": "keyValue1", "k2": "keyValue2"])
section.removeMenu(forValue: "keyValue1")
print(section)
output:
//Folder(name: "FolderName", menu: ["k2": "keyValue2"])
So first of all you need to make menu an actual variable instead of a constant, and it needs to be a dictionary of Strings to Array of Strings.
Then, you can remove entries from the array easily by getting their index and calling remove:
struct Folder {
let name:String
var menu: [String: [String]]
}
var section = Folder(name: "foo", menu: [ "hello": ["a", "b", "c"]])
if let index = section.menu["hello"]?.firstIndex(of: "a") {
section.menu["hello"]?.remove(at: index)
}
print(section.menu) // ["hello": ["b", "c"]]
Related
I have a collection called objects / documents of type Object that has an an array of type ObjectNotification, I am trying to update each notification.read to true.
I have a view that displays all the userNotifications from all objects in a single array self.viewModel.userNotifications.
When onAppear for the view I am trying to set each userNotification.read to true in self.viewModel.userNotifications and update the FirestoreDB.
However I am not sure the best approach to take, currently I am looping through the arrays and trying to update each userNotification in self.viewModel.objects.userNotifications then update the document in the DB, which will update self.viewModel.userNotifications as that fetches all self.viewModel.userNotifications.
But I get the following error as I am trying to change a struct, I was trying to change the value in my for in statement then called my updateObect(object) method to update the document in the DB.
Cannot assign through subscript: 'h' is a 'let' constant
.onAppear() {
// Mark as read
let read = objectManager.markNotificationsAsRead(self.viewModel.userNotifications)
self.viewModel.updateObjectNotifications(readNotifcations: read)
}
func markNotificationsAsRead(_ notifications: [ObjectNotification]) -> [ObjectNotification]{
// Mark notifications as read
var readNotifications: [ObjectNotification] = []
for n in notifications {
if n.read == false {
// Create new with true
var new = n
new.read = true
readNotifications.append(new)
}
}
// Return update notifications with read = true
return readNotifications
}
func updateObjectNotifications(readNotifcations: [ObjectNotification]) {
if let currentUser = Auth.auth().currentUser {
for h in self.objects {
for n in h.notifications {
if n.deliveredTo == currentUser.email {
for r in readNotifcations {
if r.id == n.id {
// same notif for home
// h.notifications.rem
if let index = h.notifications.firstIndex(of: n) {
h.notifications[index] = r // Cannot assign through subscript: 'h' is a 'let' constant
}
}
}
}
// update object in db
}
}
}
}
Instead of the approach above, how can I change the fields in the database ?
This is is a solution to the actual problem and does not address the Firebase part of the question as that was not outlined in the actual question.
I'm going to take a wild guess here as the question is incomplete but I think whatever object 'h' is in the question is a struct which contains an array property of notifications.
If so, then you can't do this within a for loop
h.notifications[index] = r
because Structs are value types, unlike classes that are reference types. That means within the for loop, the objects are a copy of the array element, not the element itself
for copyOfArrayElement in someArrayOfStructs {}
There are a few solutions; here's two. The first is to iterate over the array using an index to access the actual struct object. Suppose we have an array of fruit structs with a name and an array property
struct FruitStruct {
var name = ""
var someList = [String]()
}
var banana = FruitStruct(name: "banana", someList: ["a", "b", "c"])
var grape = FruitStruct(name: "grape", someList: ["d", "e", "f"])
var fruitsArray = [banana, grape]
then the loop to modify every fruit name to be 'Hello' and element with index of 1 within the someList to be 'World'
for i in 0..<fruitsArray.count {
fruitsArray[i].name = "Hello"
fruitsArray[i].someList[1] = "World"
}
fruitsArray.forEach { print($0.name, $0.someList) }
and the output
Hello ["a", "World", "c"]
Hello ["c", "World", "e"]
Alternately change the struct to a class (which is a reference) so you can then modify the properties directly using your existing loop.
class FruitClass {
var name = ""
var someList = [String]()
convenience init(withName: String, andArray: [String] ) {
self.init()
self.name = withName
self.someList = andArray
}
}
To search for a string included in a struct I use:
let results = myArray.filter( {$0.model.localizedCaseInsensitiveContains("bu")} )
But say the struct has several properties that I'd like to search - or maybe I'd even like to search all of them at one time. I can only filter primitive types so leaving 'model' out won't work.
Solution -------------------------
While I really liked the idea of using key paths as Matt suggested below, I ended up adding a function to my struct that made my view controller code much cleaner:
struct QuoteItem {
var itemIdentifier: UUID
var quoteNumber: String
var customerName: String
var address1: String
func quoteItemContains(_ searchString: String) -> Bool {
if self.address1.localizedCaseInsensitiveContains(searchString) ||
self.customerName.localizedCaseInsensitiveContains(searchString) ||
self.quoteNumber.localizedCaseInsensitiveContains(searchString)
{
return true
}
return false
}
Then, in my controller, quotes is an array of QuoteItem that I can search by simply writing:
searchQuoteArray = quotes.filter({ $0.quoteItemContains(searchString) })
This sounds like a job for Swift key paths. Just supply the key paths for the String properties you want to search.
struct MyStruct {
let manny = "Hi"
let moe = "Hey"
let jack = "Howdy"
}
let paths = [\MyStruct.manny, \MyStruct.moe, \MyStruct.jack]
let s = MyStruct()
let target = "y"
let results = paths.map { s[keyPath:$0].localizedCaseInsensitiveContains(target) }
// [false, true, true]
I hope i understood you correct. I think with this piece of code you can achieve what you want:
struct ExampleStruct {
let firstSearchString: String
let secondSearchString: String
}
let exampleOne = ExampleStruct(firstSearchString: "Hello", secondSearchString: "Dude")
let exampleTwo = ExampleStruct(firstSearchString: "Bye", secondSearchString: "Boy")
let exampleArray = [exampleOne, exampleTwo]
let searchString = "Hello"
let filteredArray = exampleArray.filter { (example) -> Bool in
// check here the properties you want to check
if (example.firstSearchString.localizedCaseInsensitiveContains(searchString) || example.secondSearchString.localizedCaseInsensitiveContains(searchString)) {
return true
}
return false
}
for example in filteredArray {
print(example)
}
This prints the following in Playgrounds:
ExampleStruct(firstSearchString: "Hello", secondSearchString: "Dude")
Let me know if it helps.
I have an array of dictionaries with the following type of structure (which is already sorted) :
[
[
"id": 1,
"name": "ItemA",
"url": "http://url.com"
],
[
"id": 32,
"name": "ItemB",
"url": "http://url.com"
],
...
]
Declared as an array of dictionaries for AnyObject :
var arrayApps = [[String:AnyObject]]()
This array of dictionaries is generated using SwiftyJson :
[..]
if let resData = swiftyJsonVar["data"].arrayObject {
self.arrayItems = resData as! [[String:AnyObject]]
}
[..]
My Goal is to display those items in sections by using the sections headers but after trying to figure it out and looking for an answer, i'm unable to move on.
I've tried to groupe the dictionaries by letters to get a result like this:
[
"A":{[foo1],[foo2]},
"D":{[foo3],[foo5]},
"F":{[foo4],[foo6]}
...
]
But no luck, i've always ended up with errors because my array contains "Optionals".
In summary :
How can I generate Alphabetical section headers based on the name inside a TableView using an array of dictionaries not grouped like the one given above in Swift 3 ?
Thank you in advance !!
You can use the .sorted(by: ) method of Array to compare to elements of you array with each other.
This yields a sortedArray:
let sortedArray = arrayOfApps.sorted(by: {($0["name"] as! String) <= ($1["name"] as! String)})
This will crash if the itemName is not a String but I left it to you to handle any errors. For example changing it to:
$0["name"] as? String ?? ""
EDIT:
// Removed examples and added extension to create desired result
I found one of my old projects where I wrote such extension. Changed it a bit to suit your needs, tell me if it needs some change still:
extension Array {
func sectionTitlesForArray(withName name: (Element) -> String) -> Array<(title: String, elements: NSMutableArray)> {
var sectionTitles = Array<(title: String, elements: NSMutableArray)>()
self.forEach({ element in
var appended = false
sectionTitles.forEach({ title, elements in
if title == name(element) {
elements.add(element)
appended = true
}
})
if appended == false {
sectionTitles.append((title: name(element), elements: [element]))
}
})
return sectionTitles
}
}
// Usage single letter as Section title:
let sectionTitles = arrayOfApps.sectionTitlesForArray(withName: {
let name = $0["name"] as! String
return String(name[name.startIndex])
})
// Quick dirty pretty-print:
sectionTitles.forEach({ sectionTitle in
print("Section title: \(sectionTitle.title) \n")
sectionTitle.elements.forEach({ object in
let element = object as! Dictionary<String,Any>
print("Element name: \(element["name"]!)")
})
print("")
})
Given an NSTableView that has an array of structures as its datasource. A user can click on any column heading to sort by that column. The column identifiers match the property names of the properties within the structure.
Given a structure
struct MyStructure {
var col0data = "" //name matches the column identifier
var col1data = ""
}
and an array of structures
var myArray = [MyStructure]()
The goal is that when a column heading is clicked, use that column's identifier to sort the array of structures by that column identifier/property
With an array of dictionaries, it was easy...
self.myArrayOfDictionaries.sortInPlace {
(dictOne, dictTwo) -> Bool in
let d1 = dictOne[colIdentifier]! as String;
let d2 = dictTwo[colIdentifier]! as String;
return d1 < d2 //or return d1 > d2 for reverse sort
}
The question is how to access the properties of the Structure dynamically, something like
let struct = myArray[10] as! MyStructure //get the 10th structure in the array
let value = struct["col0data"] as! String //get the value of the col0data property
If there is a better way, suggestions would be appreciated.
I should also note that the structure may have 50 properties so this is an effort to reduce the amount of code needed to sort the array by any one of those properties.
edit:
One solution is to change the structure to a class derived from NSObject. Then the properties could be accessed via .valueForKey("some key"). However, I am trying to keep this Swifty.
Maybe I have a solution to your problem. The advantage of this code over your solution is here you don't need to add a subscript method to your struct to create an hardcoded String-Property-Value map via code.
Here's my extension
extension _ArrayType {
func sortedBy(propertyName propertyName: String) -> [Self.Generator.Element] {
let mirrors = self.map { Mirror(reflecting: $0) }
let propertyValues = mirrors.map { $0.children.filter { $0.label == propertyName }.first?.value }
let castedValues = propertyValues.map { $0 as? String }
let sortedArray = zip(self, castedValues).sort { (left, right) -> Bool in
return left.1 < right.1
}.map { $0.0 }
return sortedArray
}
}
Usage
struct Animal {
var name: String
var type: String
}
let animals = [
Animal(name: "Jerry", type: "Mouse"),
Animal(name: "Tom", type: "Cat"),
Animal(name: "Sylvester", type: "Cat")
]
animals.sortedBy(propertyName: "name")
// [{name "Jerry", type "Mouse"}, {name "Sylvester", type "Cat"}, {name "Tom", type "Cat"}]
animals.sortedBy(propertyName: "type")
// [{name "Tom", type "Cat"}, {name "Sylvester", type "Cat"}, {name "Jerry", type "Mouse"}]
Limitations
The worst limitation of this solutions is that it works only for String properties. It can be change to work with any types of property by it must be at compile time. Right now I have not a solution to make it work with any king of property type without changing the code.
I already asked help for the core of the problem here.
I would definitely recommend simply embedding your dictionary into your struct. A dictionary is a much more suitable data structure for 50 key-value pairs than 50 properties – and you've said that this would be an acceptable solution.
Embedding the dictionary in your struct will give you the best of both worlds – you can easily encapsulate logic & you have have easy lookup of the values for each column ID.
You can now simply sort your array of structures like this:
struct MyStructure {
var dict = [String:String]()
init(col0Data:String, col1Data:String) {
dict["col0data"] = col0Data
dict["col1data"] = col1Data
}
}
var myArray = [MyStructure(col0Data: "foo", col1Data: "bar"), MyStructure(col0Data: "bar", col1Data: "foo")]
var column = "col0data"
myArray.sort {
$0.dict[column] < $1.dict[column]
}
print(myArray) // [MyStructure(dict: ["col0data": "bar", "col1data": "foo"]), MyStructure(dict: ["col0data": "foo", "col1data": "bar"])]
column = "col1data"
myArray.sort {
$0.dict[column] < $1.dict[column]
}
print(myArray) // MyStructure(dict: ["col0data": "foo", "col1data": "bar"])], [MyStructure(dict: ["col0data": "bar", "col1data": "foo"])
Here's an answer (but not the best answer); use subscripts to return the correct property, and set which property you are sorting by within the array.sort:
struct MyStructure {
var col0data = "" //name matches the column identifier
var col1data = ""
subscript(key: String) -> String? { //the key will be the col identifier
get {
if key == "col0data" {
return col0data
} else if key == "col1data" {
return col1data
}
return nil
}
}
}
And then here's how the sort works:
let identifier = the column identifier string,say col0data in this case
myArray.sortInPlace ({
let my0 = $0[identifier]! //the identifier from the table col header
let my1 = $1[identifier]!
return my0 < my1
})
If you do not know what types the values of MyStructure can be you will have a hard time comparing them to sort them. If you had a function that can compare all types you can have in MyStructure then something like this should work
struct OtherTypeNotComparable {
}
struct MyStructure {
var col0data = "cat" //name matches the column identifier
var col1data: OtherTypeNotComparable
}
let structures = [MyStructure(), MyStructure()]
let sortBy = "col1data"
func yourCompare(a: Any, b: Any) -> Bool {
return true
}
var expanded : [[(String, Any, MyStructure)]]
= structures.map { s in Mirror(reflecting: s).children.map { ($0!, $1, s) } }
expanded.sortInPlace { (a, b) -> Bool in
let aMatch = a.filter { $0.0 == sortBy }.first!.1
let bMatch = b.filter { $0.0 == sortBy }.first!.1
return yourCompare(aMatch, b: bMatch)
}
source: https://developer.apple.com/library/watchos/documentation/Swift/Reference/Swift_Mirror_Structure/index.html
Let's say we have an Array, assigned to a variable with the type Any
let something: Any = ["one", "two", "three"]
Let's also assume we don't know if it's an array or something entirely else. And we also don't know what kind of Array.Element we are dealing with exactly.
Now we want to find out if it's an array.
let isArray = something is Array // compiler error
let isArray = (something as? [Any?] != nil) // does not work (array is [String] and not [Any?])
Is there any elegant solution to tickle the following information out of the swift type system:
Is the given object an Array
What's the count of the array
Give me the elements of the array
(bridging to NSArray is not a solution for me, because my array could also be of type [Any?] and contain nil-values)
I love #stefreak's question and his solution. Bearing in mind #dfri's excellent answer about Swift's runtime introspection, however, we can simplify and generalise #stefreak's "type tagging" approach to some extent:
protocol AnySequenceType {
var anyElements: [Any?] { get }
}
extension AnySequenceType where Self : SequenceType {
var anyElements: [Any?] {
return map{
$0 is NilLiteralConvertible ? Mirror(reflecting: $0).children.first?.value : $0
}
}
}
extension Array : AnySequenceType {}
extension Set : AnySequenceType {}
// ... Dictionary, etc.
Use:
let things: Any = [1, 2]
let maybies: Any = [1, nil] as [Int?]
(things as? AnySequenceType)?.anyElements // [{Some 1}, {Some 2}]
(maybies as? AnySequenceType)?.anyElements // [{Some 1}, nil]
See Swift Evolution mailing list discussion on the possibility of allowing protocol extensions along the lines of:
extension<T> Sequence where Element == T?
In current practice, however, the more common and somewhat anticlimactic solution would be to:
things as? AnyObject as? [AnyObject] // [1, 2]
// ... which at present (Swift 2.2) passes through `NSArray`, i.e. as if we:
import Foundation
things as? NSArray // [1, 2]
// ... which is also why this fails for `mabyies`
maybies as? NSArray // nil
At any rate, what all this drives home for me is that once you loose type information there is no going back. Even if you reflect on the Mirror you still end up with a dynamicType which you must switch through to an expected type so you can cast the value and use it as such... all at runtime, all forever outside the compile time checks and sanity.
As an alternative to #milos and OP:s protocol conformance check, I'll add a method using runtime introspection of something (foo and bar in examples below).
/* returns an array if argument is an array, otherwise, nil */
func getAsCleanArray(something: Any) -> [Any]? {
let mirr = Mirror(reflecting: something)
var somethingAsArray : [Any] = []
guard let disp = mirr.displayStyle where disp == .Collection else {
return nil // not array
}
/* OK, is array: add element into a mutable that
the compiler actually treats as an array */
for (_, val) in Mirror(reflecting: something).children {
somethingAsArray.append(val)
}
return somethingAsArray
}
Example usage:
/* example usage */
let foo: Any = ["one", 2, "three"]
let bar: [Any?] = ["one", 2, "three", nil, "five"]
if let foobar = getAsCleanArray(foo) {
print("Count: \(foobar.count)\n--------")
foobar.forEach { print($0) }
} /* Count: 3
--------
one
2
three */
if let foobar = getAsCleanArray(bar) {
print("Count: \(foobar.count)\n-------------")
foobar.forEach { print($0) }
} /* Count: 5
-------------
Optional("one")
Optional(2)
Optional("three")
nil
Optional("five") */
The only solution I came up with is the following, but I don't know if it's the most elegant one :)
protocol AnyOptional {
var anyOptionalValue: Optional<Any> { get }
}
extension Optional: AnyOptional {
var anyOptionalValue: Optional<Any> {
return self
}
}
protocol AnyArray {
var count: Int { get }
var allElementsAsOptional: [Any?] { get }
}
extension Array: AnyArray {
var allElementsAsOptional: [Any?] {
return self.map {
if let optional = $0 as? AnyOptional {
return optional.anyOptionalValue
}
return $0 as Any?
}
}
}
Now you can just say
if let array = something as? AnyArray {
print(array.count)
print(array.allElementsAsOptional)
}
This works for me on a playground:
// Generate fake data of random stuff
let array: [Any?] = ["one", "two", "three", nil, 1]
// Cast to Any to simulate unknown object received
let something: Any = array as Any
// Use if let to see if we can cast that object into an array
if let newArray = something as? [Any?] {
// You now know that newArray is your received object cast as an
// array and can get the count or the elements
} else {
// Your object is not an array, handle however you need.
}
I found that casting to AnyObject works for an array of objects. Still working on a solution for value types.
let something: Any = ["one", "two", "three"]
if let aThing = something as? [Any] {
print(aThing.dynamicType) // doesn't enter
}
if let aThing = something as? AnyObject {
if let theThing = aThing as? [AnyObject] {
print(theThing.dynamicType) // Array<AnyObject>
}
}