I was using XCode 8.3 with swift 3.1 and I updated to Xcode 9 with swift 4, now in some classes when I use RXSwift, I have this error compiler logs:
class petViewModel {
var lastPetID: Int = 0
var refreshing = Variable<Bool>(false)
var vaccines: Results<vaccines>? = nil
let error = Variable<(Int,String)>(0,"") // Extra argument in call
let changes = Variable<([Int], [Int], [Int])>([Int](), [Int](), [Int]()) // Extra argument in call
var firstLoad = Variable<Bool>(false)
// and more code bla bla bla
}
using RXSwift what is the best way to implement it? before was compiling me without any problem, any help, please?
You can use like this :
let change1 = Variable<[Int]>([Int]())
let change2 = Variable<[Int]>([Int]())
let change3 = Variable<[Int]>([Int]())
let changes = Observable.combineLatest(change1.asObservable(), change2.asObservable(), change3.asObservable())
I received a user #biboran response in GitHub, and
the issue is that swift 4.0 currently doesn't support tuple transformations.
my Variable is not compiling because I declared it as a tuple and pass it as a variadic parameter. Just wrap it into a tuple:
let changes = Variable<([Int], [Int], [Int])>(
( // <-- this is a tuple I'm missing
[Int](),
[Int](),
[Int]()
) // <-- this is a tuple I'm missing
)
as for my combineLatest, I have to wrap the argument into a collection (using a literal for example)
Observable.combineLatest([
change1.asObservable(),
change2.asObservable(),
change3.asObservable()
])
Related
I'm trying to change the value of a global variable transferredData in the function didTransferData(_ data: Data?). My code looks like this:
var transferredData: [Double] = [0.0]
func didTransferData(_ data: Data?) {
var dataArray = [CUnsignedChar](repeating:0, count: (data?.count)!)
data?.copyBytes(to: &dataArray, count: dataArray.count)
let dataInt = dataArray.filter({ Int(String($0)) != nil }).map({ Int(String($0))! })
let dataDouble = dataInt.map { Double($0) }
print("Data double: \(dataDouble)")
transferredData = dataDouble
}
Printing transferredData inside of didTransferData returns the correct array, containing all values of dataDouble. But when I try to access it in this function later on
func returnData() -> [Double]{
print("return Data: \(transferredData)")
return transferredData
}
it returns [0.0]. I'm not sure if I'm missing something crucial here, but I thought that even if I change the value of a global variable in a function, the new value should be accessible for every other functions, too.
Thanks for any advice!!
You said that this code is inside a class. The variable transferredData is not a global, it is a member variable.
There is one of these per object of the class. I suspect that you are not using the same object to make these two calls.
You could make the member shared between all objects by declaring it static, but I think it would be better to leave as is and arrange to use the same object.
EDIT: based on comment
If you write the code
let centralInstance = CentralViewController()
You will get a new object with its own transferredData member initially set to [0.0]. You need to either
Get a reference to the same VC object that has the data
Store the data some where else in an object that you can get back (since the VC might be gone)
To hack something that works (not recommended, but to help understand)
You could move transferredData out of the class and make it an actual global variable. I would do this only to help you get past this issue and understand what's going on.
You could also make it static, which makes all of the VC's share the same instance of the transferredData
When you understand what is going on, you can try to do something a little better (at least move it to its own model object, and not in the VC at all). The next simplest thing is some kind of singleton to manage it -- this is just a glorified global variable but puts you more on the road to a more typical solution.
Where is the problem:
$ swift
Welcome to Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1). Type :help for assistance.
1> var data:[Double] = [0.0]
2.
3. class MuckWithData {
4.
5. func showData () -> [Double] {
6. print ("Data: \(data)")
7. return data
8. }
9.
10. func modifyData () {
11. data = [1.0]
12. }
13. }
data: [Double] = 1 value {
[0] = 0
}
14>
15> var mucked = MuckWithData()
mucked: MuckWithData = {}
16> mucked.showData()
Data: [0.0]
$R0: [Double] = 1 value {
[0] = 0
}
17> mucked.modifyData()
18> mucked.showData()
Data: [1.0]
$R1: [Double] = 1 value {
[0] = 1
}
Probably your computation for dataDouble is actually [0.0] and thus it appears that transferredData didn't change, but it did.
I am trying to learn Swift -- current task is making a simple menu for a Mac app from an array of objects that contain strings. The problem now is how to pass the selector, which in the array is a string, but in the code is a function.
The class is
class menuArrayObject
{
var title: String = ""
var subMenuTitles: [String] = []
var subMenuSelectors: [String] = []
}
Here is my code
for index2 in 0...counter2 - 1
{
let subMenuTitle = arrayObject.subMenuTitles[index2]
let subMenuSelector = NSSelectorFromString(arrayObject.subMenuSelectors[index2])
let subMenu = NSMenuItem(title: subMenuTitle, action: #selector(subMenuSelector(_:)),keyEquivalent: "")
indexMenu.addItem(subMenu)
}
The error message (on let subMenu =) is: "argument of #selector cannot refer to a property"
Is this do-able? Is this desirable to actually do? Is there a better way?
Thanks in advanceemphasized text
What you are trying to do is totally legit – you can indeed convert a string to a selector, then pass that selector to a menu item.
You're however trying to use the selector literal syntax to initialise a Selector, giving that language construct a Selector as an argument (which is just syntactically wrong), where in fact you can just pass the Selector returned by NSSelectorFromString to the NSMenuItem initialiser call.
The selector literal syntax #selector is used when you have a "fixed" selector in mind that you want to create a Selector for (for instance an instance method of the class you are in). The NSSelectorFromString is intended for this kind of cases like yours where the selector is a variable (now that in Swift 2.2 there is indeed some syntax given for #selector literals!)
import Cocoa
class MenuArrayObject
{
var title: String = "Foo"
var subMenuTitles: [String] = ["foo"]
var subMenuSelectors: [String] = ["foobar"]
}
let menuArrayObject = MenuArrayObject()
let indexMenu = NSMenu()
for (i, submenuTitle) in menuArrayObject.subMenuTitles.enumerate() {
let selectorStr = menuArrayObject.subMenuSelectors[i]
let selector = NSSelectorFromString(selectorStr)
let item = NSMenuItem(title: submenuTitle, action: selector, keyEquivalent: "")
indexMenu.addItem(item)
}
I am new to Swift.
I am trying to get some data from a webservice and to loop the JSON data to make a simple array.
DataManager.getDataFromEndpoint{ (endpointData) -> Void in
let json = JSON(data: endpointData)
if let programsOnAir = json["data"]["data"]["on_air"].array{
var onAirArray = []
for onAir in programsOnAir {
var eventName = onAir["event_name"].string
var eventCover = onAir["event_cover"].string
var tuple = (name: eventName!, cover: eventCover!)
onAirArray.insert(tuple, atIndex: 1)
}
println(onAirArray)
}
}
I get an error where the member .insert does not exist
BUt if I init the array like this var onAirArray = [name: "something, cover: "somethingelse"] then it works.
I need to work with empty arrays and I need to be them mutable, because I have no idea what I may get from the JSON given by the API endpoint.
What am I doing wrong?
The problem is with this line:
var onAirArray = []
Since you haven't given the array an explicit type, this is creating a new instance of NSArray, which doesn't have a method called insert. Which is why this is probably the exact error message you're receiving.
'NSArray' does not have a member named 'insert'
To fix this, explicitly state the type of your array.
var onAirArray: [(String, String)] = []
I’m new to Swift and have been having some troubles figuring out some aspects of Arrays and Dictionaries.
I have an array of dictionaries, for which I have used Type Aliases - e.g.
typealias myDicts = Dictionary<String, Double>
var myArray : [myDicts] = [
["id":0,
"lat”:55.555555,
"lng”:-55.555555,
"distance":0],
["id":1,
"lat": 44.444444,
"lng”:-44.444444,
"distance":0]
]
I then want to iterate through the dictionaries in the array and change the “distance” key value. I did it like this:
for dict:myDicts in myArray {
dict["distance"] = 5
}
Or even specifically making sure 5 is a double with many different approaches including e.g.
for dict:myDicts in myArray {
let numberFive : Double = 5
dict["distance"] = numberFive
}
All my attempts cause an error:
#lvalue $T5' is not identical to '(String, Double)
It seems to be acting as if the Dictionaries inside were immutable “let” rather than “var”. So I randomly tried this:
for (var dict:myDicts) in myArray {
dict["distance"] = 5
}
This removes the error and the key is indeed assigned 5 within the for loop, but this doesn't seem to actually modify the array itself in the long run. What am I doing wrong?
The implicitly declared variable in a for-in loop in Swift is constant by default (let), that's why you can't modify it directly in the loop.
The for-in documentation has this:
for index in 1...5 {
println("\(index) times 5 is \(index * 5)")
}
In the example above, index is a constant whose value is automatically
set at the start of each iteration of the loop. As such, it does not
have to be declared before it is used. It is implicitly declared
simply by its inclusion in the loop declaration, without the need for
a let declaration keyword.
As you've discovered, you can make it a variable by explicitly declaring it with var. However, in this case, you're trying to modify a dictionary which is a struct and, therefore, a value type and it is copied on assignment. When you do dict["distance"] = 5 you're actually modifying a copy of the dictionary and not the original stored in the array.
You can still modify the dictionary in the array, you just have to do it directly by looping over the array by index:
for index in 0..<myArray.count {
myArray[index]["distance"] = 5
}
This way, you're sure to by modifying the original dictionary instead of a copy of it.
That being said, #matt's suggestion to use a custom class is usually the best route to take.
You're not doing anything wrong. That's how Swift works. You have two options:
Use NSMutableDictionary rather than a Swift dictionary.
Use a custom class instead of a dictionary. In a way this is a better solution anyway because it's what you should have been doing all along in a situation where all the dictionaries have the same structure.
The "custom class" I'm talking about would be a mere "value class", a bundle of properties. This was kind of a pain to make in Objective-C, but in Swift it's trivial, so I now do this a lot. The thing is that you can stick the class definition for your custom class anywhere; it doesn't need a file of its own, and of course in Swift you don't have the interface/implementation foo to grapple with, let alone memory management and other stuff. So this is just a few lines of code that you can stick right in with the code you've already got.
Here's an example from my own code:
class Model {
var task : NSURLSessionTask!
var im : UIImage!
var text : String!
var picurl : String!
}
We then have an array of Model and away we go.
So, in your example:
class MyDict : NSObject {
var id = 0.0
var lat = 0.0
var lng = 0.0
var distance = 0.0
}
var myArray = [MyDict]()
let d1 = MyDict()
d1.id = 0
d1.lat = 55.55
d1.lng = -55.55
d1.distance = 0
let d2 = MyDict()
d2.id = 0
d2.lat = 44.44
d2.lng = -44.44
d2.distance = 0
myArray = [d1,d2]
// now we come to the actual heart of the matter
for d in myArray {
d.distance = 5
}
println(myArray[0].distance) // it worked
println(myArray[1].distance) // it worked
Yes, the dictionary retrieved in the loop is immutable, hence you cannot change.
I'm afraid your last attempt just creates a mutable copy of it.
One possible workaround is to use NSMutableDictionary:
typealias myDicts = NSMutableDictionary
Have a class wrapper for the Swift dictionary or array.
class MyDictionary: NSObject {
var data : Dictionary<String,Any>!
init(_ data: Dictionary<String,Any>) {
self.data = data
}}
MyDictionary.data
I'm experimenting with SpriteKit in Swift but somehow seem unable to create an array of actions to use in a sequence. I've split it up to try and pin-point the problem, but no luck so far.
func animateBackground(){
let moveLeft = SKAction.moveByX(100, y: 0, duration: 3)
moveLeft.timingMode = SKActionTimingMode.EaseInEaseOut
let moveRight = SKAction.reversedAction(moveLeft)
let actions = [moveLeft, moveRight] // <--- here there be dragons/trouble
let sequence = SKAction.sequence(actions)
let repeat = SKAction.repeatActionForever(sequence)
}
When trying to create the actions-array I get the error "Cannot convert the expression's type 'Array' to type 'ArrayLiteralConvertible' " So, I thought I might need to be more explicit and attempted to change it to
var actions: SKAction[] = [moveLeft, moveRight]
This seemed to bring down the house, and not in a good way, resulting in the SourceKit terminated bug...
You're adding a function to the array for moveRight, not the SKAction itself. Try using this instead:
let moveRight = SKAction.reversedAction(moveLeft)()
When you create moveRight you're actually generating a function. You can call the function with "()" to get the actual SKAction. I added explicit types to the two SKAction's so it's clear that they can be put in an SKAction[]:
let moveLeft:SKAction = SKAction.moveByX(100, y: 0, duration: 3)
moveLeft.timingMode = SKActionTimingMode.EaseInEaseOut
let moveRight:SKAction = moveLeft.reversedAction()
let actions = [moveLeft, moveRight]
let sequence = SKAction.sequence(actions)
let repeat = SKAction.repeatActionForever(sequence)