I'm trying to loop through an (as I would interpret) array by arrayname.count like:
if var storedToDoItems: AnyObject? = NSUserDefaults.standardUserDefaults().objectForKey("toDoItems") {
toDoItems = []
for var i = 0; storedToDoItems.count; i++ {
toDoItems.append(storedToDoItems[i] as NSString)
}
}
and receive the error in the title marked by storedToDoItems.count. I'm populating first storedToDoItems like this:
...
toDoItems.append(tb_toDoItem.text)
let fixedToDoItems = toDoItems
// Store items
NSUserDefaults.standardUserDefaults().setObject(fixedToDoItems, forKey: "toDoItems")
// Save the stored stuff
NSUserDefaults.standardUserDefaults().synchronize()
...
If you store an array to the user defaults, you should try to cast it to an array when you extract it.
If toDoItems is defined as an array of strings [String], then you just have to use optional binding combined with optional cast, and just copy the extracted array to toDoItems:
if let storedToDoItems: [String] = NSUserDefaults.standardUserDefaults().objectForKey("toDoItems") as? [String] {
toDoItems = storedToDoItems
}
Being an array a struct, i.e. a value type, it is assigned by copy, so when assign storedToDoItems to toDoItems, a copy of it is created and assigned - so you don't need to manually add each element individually.
Your code instead has 2 errors:
you have defined storedToDoItems as an optional AnyObject, and optionals don't have a count property.
even if it is not defined as optional, AnyObject doesn't have a count property as well. It's irrelevant that the actual type stored in the variable is an array, the variable is declared as AnyObject and that is how is treated by the compiler.
You need to tell what's inside:
toDoItems = [String]()
if let storedToDoItems = NSUserDefaults.standardUserDefaults().objectForKey("toDoItems") as? [String] {
for item in storedToDoItems {
toDoItems.append(item)
}
}
and even shorter:
toDoItems = [String]()
if let storedToDoItems = NSUserDefaults.standardUserDefaults().objectForKey("toDoItems") as? [String] {
toDoItems = storedToDoItems
}
I just used this Bold line will work for you hopefully
if var toDoStored: [String] = NSUserDefaults.standardUserDefaults().objectForKey("toDoSaved") as? [String]{
tblItems = []
for var i = 0; i < toDoStored.count ; ++i {
tblItems.append(toDoStored[i] as NSString)
}
}
Related
I would like to know how I can make a key of a dictionary have multiple values according to the data that comes to it.
Attached basic example:
var temp = [String: String] ()
temp ["dinningRoom"] = "Table"
temp ["dinningRoom"] = "Chair"
In this case, I always return "Chair", the last one I add, and I need to return all the items that I am adding on the same key.
In this case, the "dinningRoom" key should have two items that are "Table" and "Chair".
You can use Swift Tuples for such scenarios.
//Define you tuple with some name and attribute type
typealias MutipleValue = (firstObject: String, secondObject: String)
var dictionary = [String: MutipleValue]()
dictionary["diningRoom"] = MutipleValue(firstObject: "Chair", secondObject: "Table")
var value = dictionary["diningRoom"]
value?.firstObject
You can declare a dictionary whose value is an array and this can contain the data you want, for example:
var temp = [String: [String]]()
temp["dinningRoom"] = ["Table", "Chair", "Bottle"]
If you want to add a new element you can do it this way:
if temp["dinningRoom"] != nil {
temp["dinningRoom"]!.append("Flower")
} else {
temp["dinningRoom"] = ["Flower"]
}
Now temp["dinningRoom"] contains ["Table", "Chair", "Bottle", "Flower"]
Use Dictionary like this:
var temp = [String: Any]()
temp["dinningRoom"] = ["Table", "Chair"]
If you want to fetch all the elements from dinningRoom. You can use this:
let dinningRoomArray = temp["dinningRoom"] as? [String]
for room in dinningRoomArray{
print(room)
}
It is not compiled code but I mean to say that we can use Any as value instead of String or array of String. When you cast it from Any to [String]
using as? the app can handle the nil value.
I'm saving lists in a dictionary. These lists need to be updated. But when searching for an item, I need [] operator. When I save the result to a variable, a copy is used. This can not be used, to change the list itself:
item = dicMyList[key]
if item != nil {
// add it to existing list
dicMyList[key]!.list.append(filename)
// item?.list.append(filename)
}
I know, that I need the uncommented code above, but this accesses and searches again in dictionary. How can I save the result, without searching again? (like the commented line)
I want to speed up the code.
In case you needn't verify whether the inner list was actually existing or not prior to adding element fileName, you could use a more compact solution making use of the nil coalescing operator.
// example setup
var dicMyList = [1: ["foo.sig", "bar.cc"]] // [Int: [String]] dict
var key = 1
var fileName = "baz.h"
// "append" (copy-in/copy-out) 'fileName' to inner array associated
// with 'key'; constructing a new key-value pair in case none exist
dicMyList[key] = (dicMyList[key] ?? []) + [fileName]
print(dicMyList) // [1: ["foo.sig", "bar.cc", "baz.h"]]
// same method used for non-existant key
key = 2
fileName = "bax.swift"
dicMyList[key] = (dicMyList[key] ?? []) + [fileName]
print(dicMyList) // [2: ["bax.swift"], 1: ["foo.sig", "bar.cc", "baz.h"]]
Dictionaries and arrays are value types. So if you change an entry you'll need to save it back into the dictionary.
if var list = dicMyList[key] {
list.append(filename)
dicMyList[key] = list
} else {
dicMyList[key] = [filename]
}
It's a little bit late, but you can do something like this:
extension Optional where Wrapped == Array<String> {
mutating func append(_ element: String) {
if self == nil {
self = [element]
}
else {
self!.append(element)
}
}
}
var dictionary = [String: [String]]()
dictionary["Hola"].append("Chau")
You can try this in the Playground and then adapt to your needs.
So here I have a basic setup
var preferenceSpecification = [String : String?]()
preferenceSpecification["Key"] = "Some Key"
preferenceSpecification["Some Key"] = nil
preferenceSpecification["DefaultValue"] = "Some DefaultValue"
print(preferenceSpecification)
var defaultsToRegister = [String : String]()
if let key = preferenceSpecification["Key"], let defaultValueKey = preferenceSpecification["DefaultValue"] {
defaultsToRegister[key] = preferenceSpecification[defaultValueKey]!
}
But the error points out where it demands that I force unwrap this, to be like this:
defaultsToRegister[key!] = preferenceSpecification[defaultValueKey!]!
Which doesn't make sense, because keyValue and defaultValue already are unwrapped
When you extract a value from a dictionary like this using subscript
[String: String?]
you need to manage 2 levels of optional. The first one because the subscript returns an optional. The second one because the value of you dictionary is an optional String.
So when you write
if let value = preferenceSpecification["someKey"] {
}
you get value defined as an optional String.
Here's the code to fix that
if let
optionalKey = preferenceSpecification["Key"],
key = optionalKey,
optionalDefaultValueKey = preferenceSpecification["DefaultValue"],
defaultValueKey = optionalDefaultValueKey,
value = preferenceSpecification[defaultValueKey] {
defaultsToRegister[key] = value
}
Suggestions
You should avoid force unwrapping as much as possible. Instead you managed to put 3 ! on a single line!
You should also try to use better name for your constants and variables.
You could also define an extension which helps get rid of the double optional situation.
extension Dictionary where Value == Optional<String> {
func flattened(_ key: Key) -> Value {
if let value = self[key] {
return value
}
return nil
}
}
Usage: preferenceSpecification.flattened("someKey")
This is how I declared my dictionary:
var dataDictionary: [NSIndexPath:[Int:Bool]]!
The inner dictionary will always have just one entry e.g. [1:true]. When I search dataDictionary I specify a NSIndexPath. The inner dictionary gets returned. Sth like this:
var innerDictionary = dataDictionary[indexPath] // is of type [Int:Bool]
I would like to access inner dictionarys key and value, but I don't want to specify an Integer or Bool, because it is unknown. I only want to get that Int and/or Bool value stored in inner dictionary. No search of inner dictionary is needed, because if will always contains just one entry. Maybe something like this:
var key = innerDictionary.key
var value = innerDictionary.value
How can this be accomplished?
If your dictionary has only one entry, and you don't know the key, with Swift 2 you can get the first element of the keys sequence safely with if let:
let innerDictionary = [42: true]
if let k = innerDictionary.keys.first {
print(k) // prints 42
} else {
// dict is empty
}
Same for the value:
if let v = innerDictionary.values.first {
print(v) // prints true
} else {
// key has no value
}
Try by this way:
func nestedDic(){
var innerDictionary:NSDictionary = ["Item 1": "data 0", "Item 2": "data 1"]
//NSLog("original object:\(innerDictionary)")
NSLog("all keys array:\(innerDictionary.allKeys)")
if(innerDictionary.isKindOfClass(NSDictionary)){
for key in innerDictionary.allKeys{
let value = innerDictionary.valueForKey(key as! NSString as String)
NSLog("key value = \(value as! String)")
}
}
}
You could create a simple struct for the inner dictionary if there is only one entry, then you are able to use your favorite property names.
struct InnerDictionary {
var key = 0
var value = false
}
let indexPath = NSIndexPath(index: 1)
var dataDictionary = [indexPath: InnerDictionary(key: 1, value: true)]
if let innerDictionary = dataDictionary[indexPath] {
var key = innerDictionary.key
var value = innerDictionary.value
}
I want to initialize a dictionary with a dictionary nested inside like this:
var a = [Int:[Int:Float]]()
a[1][2] = 12
But I get an error:
(Int:[Int:Float]) does not have a member named 'subscript'
I've hacked at a variety of other approaches, all of them running into some kind of issue.
Any idea why this doesn't work?
You can create your own 2D dictionary like this:
struct Dict2D<X:Hashable,Y:Hashable,V> {
var values = [X:[Y:V]]()
subscript (x:X, y:Y)->V? {
get { return values[x]?[y] }
set {
if values[x] == nil {
values[x] = [Y:V]()
}
values[x]![y] = newValue
}
}
}
var a = Dict2D<Int,Int,Float>()
a[1,2] = 12
println(a[1,2]) // Optional(12.0)
println(a[0,2]) // nil
The point is you access the element via a[x,y] instead of a[x][y] or a[x]?[y].
It's giving you that error because your first subscript returns an optional so it may return a dictionary or nil. In the case that it returns nil the second subscript would be invalid. You can force it to unwrap the optional value by using an exlamation point.
var a = [1 : [ 2: 3.14]]
a[1]
a[1]![2]
If you aren't positive that a[1] is non-nil you may want to safely unwrap with a question mark instead.
var a = [1 : [ 2: 3.14]]
a[1]
a[1]?[2]
You can also assign using this method. (As of Beta 5)
var a = [Int:[Int:Float]]()
a[1] = [Int: Float]()
a[1]?[2] = 12.0
a[1]?[2] //12.0
Another way to do it is with an extension to the standard dictionary:
extension Dictionary {
mutating func updateValueForKey(key: Key, updater: ((previousValue: Value?) -> Value)) {
let previousValue = self[key]
self[key] = updater(previousValue: previousValue)
}
}
Example:
var a = [Int:[Int:Float]]()
a.updateValueForKey(1) { nestedDict in
var nestedDict = nestedDict ?? [Int:Float]()
nestedDict[2] = 12
return nestedDict
}