var readIndicatorNeedsDisplay: Driver<Bool> = .empty()
public func bindcellEvents(readNotificationID: String) {
if let unreadNotificationIDs = UserDefaults.main?.unreadNotificationIDs, unreadNotificationIDs.contains(readNotificationID) {
readIndicatorNeedsDisplay = true
} else {
UserDefaults.main?.unreadNotificationIDs.append(readNotificationID)
readIndicatorNeedsDisplay = false
// Cannot assign value of type 'Bool' to type 'Driver<Bool>' (aka 'SharedSequence<DriverSharingStrategy, Bool>')
}
}
when i assign bool to driver Giving error: Cannot assign value of type 'Bool' to type 'Driver' (aka 'SharedSequence')
You're not supposed to assign values directly to a Driver, and attempting to do so shows your fundamental misunderstanding of RxSwift. You should probably step back, and learn the basics, then come back to this problem.
However, if you want to feed values to a stream, you could use a PublishRelay:
var readIndicatorNeedsDisplay = PublishRelay<Bool>()
public func bindcellEvents(readNotificationID: String) {
if let unreadNotificationIDs = UserDefaults.main?.unreadNotificationIDs, unreadNotificationIDs.contains(readNotificationID) {
readIndicatorNeedsDisplay.accept(true)
} else {
UserDefaults.main?.unreadNotificationIDs.append(readNotificationID)
readIndicatorNeedsDisplay.accept(false)
}
}
Related
I'm trying to do validation on my form struct in a method that returns a bool, but I keep getting false even when it should be returning true..
If you look towards the end of the Validate method, you'll see I write validated := len(this.Errors) == 0 which should be making "validated" either true or false based on whether the Errors map has items or not, and then I return validated.
When I fill out my form accurately, there should be no errors yet I still get false when I should be getting true.
Can someone explain? Is this not how Go works?
form.go:
package models
import (
"../config"
"../util"
)
type Form struct {
Name string
Email string
Phone string
Message string
Thanks string
ErrorHandler
}
func (this *Form) Validate() bool {
this.Errors = make(map[string]string)
matched := util.MatchRegexp(".+#.+\\..+", this.Email)
if !util.IsEmpty(this.Email) {
if matched == false {
this.Errors["Email"] = config.EMAIL_INVALID
}
} else {
this.Errors["Email"] = config.EMAIL_EMPTY
}
if util.IsEmpty(this.Name) {
this.Errors["Name"] = config.NAME_EMPTY
}
if util.IsEmpty(this.Phone) {
this.Errors["Phone"] = config.PHONE_EMPTY
}
if util.IsEmpty(this.Message) {
this.Errors["Message"] = config.MESSAGE_EMPTY
}
validated := len(this.Errors) == 0
if validated {
this.Thanks = config.THANK_YOU
}
return validated
}
errorhandler.go:
package models
type ErrorHandler struct {
Errors map[string]string
}
func (this *ErrorHandler) HandleErr(err string) {
this.Errors = make(map[string]string)
this.Errors["Error"] = err
}
And this is where I try to call the Validate method -- in a function in my controller:
form := &models.Form{
Name: r.FormValue("name"),
Email: r.FormValue("email"),
Phone: r.FormValue("phone"),
Message: r.FormValue("message")}
if form.Validate() {
// This never runs because 'form.Validate()' is always false
}
I don't think the util.IsEmpty() is the culprit here.. just checks if the string is empty:
func IsEmpty(str string) bool {
return strings.TrimSpace(str) == ""
}
Any help would be appreciated!
It's best to debug this kind of problem with a log statement like:
log.Printf("form: %v", form)
before calling validate, so it's clear what the input data looks like.
Greetings, Philip
func reloadFriendList() {
var query = PFQuery(className:"userFriendClass")
query.whereKey("username", equalTo:user!.username!)
query.findObjectsInBackgroundWithBlock {
(objects: [PFObject]?, error: NSError?) -> Void in
if error == nil {
for object in objects! {
self.friendList = object["friends"] as! [String]
print(self.friendList)
self.reloadTableView()
}
} else {
// Log details of the failure
print("Error: \(error!) \(error!.userInfo)")
}
}
}
i want to save object["friends"] that is an array from parse with usernames into
var friendList = [String]()
but i get the error: "fatal error: unexpectedly found nil while unwrapping an Optional value",
when the array is empty which means the user doesn't have any friends yet it works fine when the user have at least 1 or more friends.
You need to have your code ready to handle nil cases and cases where "objects" is an empty array.
If this were my code, I would do something like:
for object in objects {
if let friendList = object["friends"]
{
self.friendList = friendList
} else {
// make sure that your class's `friendList` var is declared as an optional
self.friendList = [String]()
}
}
Since objects is optional and may be nil, you need to unwrap it safely. One way to do that is to use the nil coalescing operator to unwrap it or to substitute an empty array if objects is nil. You can use it again to safely unwrap the list of friends:
for object in objects ?? [] {
self.friendList = (object["friends"] as? [String]) ?? []
You can also use optional binding if let to safely unwrap things:
if let unwrappedObjects = objects {
for object in unwrappedObjects {
if let friends = object["friends"] as? [String] {
self.friendsList = friends
} else {
// no friends :-(
self.friendsList = []
}
}
}
Currently I'm working on my new App written with Swift 2.0. Today I faced two strange errors in Xcode beta 5. I'd love if someone with a previous beta version of Xcode can confirm if I'm right or not. I also could misunderstand something, so I'll appreciate any feedback.
Here is some example code that made me struggle a while:
// Frist bug
protocol SomeProtocol {
var someArray: [String] { get set } // #1 bug
}
extension SomeProtocol {
func someFunction(someString: String) {
self.someArray.append(someString) // #1: Immutable value of type '[String]' only has mutating members named 'append'
}
}
// Second bug
protocol SomeInterfaceProtocol {
var someBool: Bool { get set } // #2 bug
}
class SomeClass: SomeInterfaceProtocol {
var someBool: Bool = false
func returnInterface() -> SomeInterfaceProtocol {
return self
}
}
let someInstance = SomeClass()
// can't set the value
someInstance.returnInterface().someBool = true // #2: Cannot assign to property: function call returns immutable value
The first error can be solved if you add the modifier mutating before the extension func declaration like this:
mutating func someFunction(someString: String) {
I suspect that's a change in the language.
The other one puzzles me as well. At least, here's a work-around:
var c = someInstance.returnInterface()
c.someBool = true
I think the second one isn't a bug as well for the same reason that you can't modify an item in a dictionary directly, or that you can't change elem in for elem in array { ... }.
Something has to be saved to be able to change it. Because you're returning the protocol type, the compiler can't know whether it's a struct or a class, whereas if it's a struct the operation of changing it would have no effect because it's not persisted in any way and structs aren't passed by reference. That's why Thomas' workaround works. Maybe it'll work too if returnInterface returned a class instance, instead of the protocol type.
EDIT: Just tried it out: Indeed it works either if you return SomeClass instead of SomeInterfaceProtocol or if you change the protocol to a class protocol, as it can't be a struct
protocol SomeInterfaceProtocol : class {
var someBool: Bool { get set }
}
class SomeClass: SomeInterfaceProtocol {
var someBool: Bool = false
func returnInterface() -> SomeInterfaceProtocol {
return self
}
}
or
protocol SomeInterfaceProtocol {
var someBool: Bool { get set }
}
class SomeClass: SomeInterfaceProtocol {
var someBool: Bool = false
func returnInterface() -> SomeClass {
return self
}
}
both work
(first post)
usually im able to find answers here or elsewhere but no luck this time =(
Question: in Swift, how do you filter an array that is of a protocol type by an implementing type supplied as a function parameter?
protocol Aprotocol {
var number:Int { get set }
}
class Aclass: Aprotocol {
var number = 1
}
class AnotherClass: Aprotocol {
var number = 1
}
var array:[Aprotocol] = [ Aclass(), AnotherClass(), Aclass() ]
func foo (parameter:Aprotocol) -> Int {
return array.filter({ /* p in p.self == parameter.self */ }).count
}
var bar:Aprotocol = // Aclass() or AnotherClass()
var result:Int = foo(bar) // should return 2 or 1, depending on bar type
maybe this is not the right approach at all?
thanks!
Here is what I think you want:
return array.filter { (element: Aprotocol) -> Bool in
element.dynamicType == parameter.dynamicType
}.count
But I recommend this, which does the same, but without the useless instance of Aclass() which is passed in the answer on the top. Also this way is faster:
func foo <T: Aprotocol>(type: T.Type) -> Int {
return array.filter { (element: Aprotocol) -> Bool in
element.dynamicType == type
}.count
}
var result:Int = foo(Aclass)
The dynamicType will return the Type of an instance
Very easy:
return array.filter({ parameter.number == $0.number }).count
Kametrixoms solution works (if you use "is T" instead of "== type") but in my case, since i didnt know which implementing class was going to call it, had to go with this solution:
protocol Aprotocol: AnyObject {
var number:Int { get set }
}
class func foo(parameter: AnyObject) -> Int {
return array.filter ({ (element: Aprotocol) -> Bool in
object_getClassName(element) == object_getClassName(parameter)
}).count
}
I'm trying to have variables in swift that are critical app-wide user settings so they must be persisted to disk after every change. There is a small amount of these variables and I'm content with the first read happening from disk after the app starts.
I have code that looks similar to this:
var _myEnumMember:MyEnum?
var myEnumMember:MyEnum {
get {
if let value = _myEnumMember { // in memory
return value
}
var c:Cache = Cache()
var storedValue:MyEnum? = c.get("SomeStorageKey");
if let value = storedValue { // exists on disk
self.myEnumMember = value // call setter to persist
return self.myEnumMember // call getter again with value set
}
self.myEnumMember = .DefaultValue // assign via setter
return self.rankingDuration // call getter after `set`
}
set (newValue){
self._myEnumMember = newValue // assign to memory
var c:Cache = Cache()
c.put("SomeStorageKey", data: ser) // store in disk
}
I have about 5-6 properties that need to do this - I don't want to repeat myself over and over - is there any way to DRY this code up so I won't have to repeat this logic in several places?
(Note: Asking here and not CR.SE because I'd like answers to explain how to DRY getters/setters in these situations rather than receive critique on a particular piece of code)
I was working on something similar recently - this may be your best bet. I used this as a nested struct, but it doesn't strictly need to be nested.
First, define a LocalCache type that will handle the persistence of your properties:
struct LocalCache {
// set up keys as constants
// these could live in your class instead
static let EnumKey = "EnumKey"
static let IntKey = "IntKey"
static let StringKey = "StringKey"
// use a single cache variable, hopefully?
var cache = Cache()
// in-memory values go in a Dictionary
var localValues: [String: Any] = [:]
// fetch from local storage or from disk
// note that the default value also sets the return type
mutating func fetch<T>(key: String, defaultValue: T) -> T {
if localValues[key] == nil {
localValues[key] = cache.get(key) ?? defaultValue
}
return localValues[key]! as T
}
// save in both local storage and to disk
mutating func store(key: String, _ value: Any) {
localValues[key] = value
cache.put(key, data: value)
}
}
Then add a LocalCache instance to your class, and you can have much simpler getter/setters.
class Test {
// instance of the local cache
var localCache = LocalCache()
var enumPropery: MyEnum {
get { return localCache.fetch(LocalCache.EnumKey, defaultValue: MyEnum.DefaultValue) }
set { localCache.store(LocalCache.EnumKey, newValue) }
}
var intProperty: Int {
get { return localCache.fetch(LocalCache.IntKey, defaultValue: 0) }
set { localCache.store(LocalCache.IntKey, newValue) }
}
var stringProperty: String {
get { return localCache.fetch(LocalCache.StringKey, defaultValue: "---") }
set { localCache.store(LocalCache.StringKey, newValue) }
}
}
If you're using swift in an iOS or OS X context then NSUserDefaults are ABSOLUTELY the right way to do this.
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/index.html
http://www.codingexplorer.com/nsuserdefaults-a-swift-introduction/