I am working with two large arrays containing following data:
print(dataID[1]) // ["DataID123"]
print(dataAR[1]) // ["73.075584"]
I'd like to form a dictionary from the two arrays by:
var arrayofDict = [String: AnyObject?]()
for i in 0...csvDataID.count {
if i < csvDataID.count {
let key = csvDataID[i]
let value = csvDataAG[i]
arrayofDict[key] = value
}
}
But get following error:
Cannot subscript a value to '[String: AnyObject?]' with an index of
type '[String]'
I also tried a few other approaches aswell resulting in the same error.
Could anyone help me and is there even a more efficient way to handle the arrays?
Thanks!
let key = csvDataID[i][0]
let value = csvDataAG[i][0]
Explaination:
The log says that csvDataID[1] is an array: ["DataID123"]
The same is for the second one.:["73.075584"]
So,
let key = csvDataID[i] // you set the key is array.
That's why you can see this error.
Related
The problem with the ECMA standard for sort of Object.keys() is known:
Object.keys() handle all keys with integer (example: 168), including integer as strings (example: "168"), as a integer. The result is, both are the same (168 === "168"), and overwrite itself.
var object = {};
object["168"] = 'x';
object[168] = 'y';
Object.keys(object); // Array [ "168" ]
object[Object.keys(object)]; // "y"
Interestingly, all keys (including pure integer keys) are returned as a string.
The ecma262 wrote about this: All keys will be handle as a integer, expect the key is a String but is not an array index.
https://tc39.es/ecma262/#sec-ordinaryownpropertykeys
That should tell us: 168 === "168". A toString() do not solve the problem.
var object = {};
object[[3].toString()] = 'z';
object[[1].toString()] = 'x';
object[[2].toString()] = 'y';
Object.keys(object);
// Array(3) [ "1", "2", "3" ]
Paradoxically, in this case, only integer apply as "enumerable" (it's ignoring array.sort(), that sort also strings with letters.).
My question about this is simple: How can i prevent the sort function in Object.keys()? I have testet the Object.defineProperties(object, 1, {value: "a", enumerable: true/false}), but that mean not realy enumerable in the case of integer or string or integer-like string. It means only should it be counted with or not. It means "counted" like omit (if it false), not "enumerabled" like ascending or descending.
A answere like that is not a good answer: Please use only letters [a-zA-Z] or leastwise a letter at the first position of keyword.
What I want: That the keys are not sorted, but output in the order in which they were entered, whether integer, string or symbol.
Disclaimer: Please solutions only in JavaScript.
Javascript Objects are unordered by their nature. If you need an ordered object-like variable I would suggest using a map.
To achieve what you're looking for with a map instead of object you'd do something like the below:
var map1 = new Map();
map1.set("123", "c");
map1.set(123, "b");
var iterator1 = map1.keys();
var myarray = [];
for (var i = 0; i < map1.size; i++) {
myarray.push(iterator1.next().value);
}
console.log(myarray);
// Array ["123", 123]
Unfortunately it's not compatible with IE and I'm not sure how else you could achieve what you need without it. A quick Google did return something about jQuery maps, though.
If you don't want to use jQuery and still need to support IE some points are below:
Is there anything stopping you using an array rather than JS object to store the data you need? This will retain the order per your requirements unlike objects. You could have an object entry in each iteration which represents the key then use a traditional foreach to obtain them as an array. I.e.
The array:
var test_array = [
{key: 123, value: 'a value here'},
{key: "123", value: 'another value here'}
];
// console.log(test_array);
Getting the keys:
var test_array_keys = [];
test_array.forEach(function(obj) { test_array_keys.push(obj['key']); } );
// console.log(test_array_keys);
Then if you needed to check whether the key exists before adding a new entry (to prevent duplicates) you could do:
function key_exists(key, array)
{
return array.indexOf(key) !== -1;
}
if(key_exists('12345', test_array_keys))
{
// won't get here, this is just for example
console.log('Key 12345 exists in array');
}
else if(key_exists('123', test_array_keys))
{
console.log('Key 123 exists in array');
}
Would that work? If not then the only other suggestion would be keeping a separate array alongside the object which tracks the keys and is updated when an entry is added or removed to/from the object.
Object Keys sorted and store in array
First Creating student Object. then sort by key in object,last keys to store in array
const student={tamil:100, english:55, sci:85,soc:57}
const sortobj =Object.fromEntries(Object.entries(student).sort())
console.log(Object.keys(sortobj))
use map instead of an object.
let map = new Map()
map.set("a", 5)
map.set("d", 6)
map.set("b", 12)
to sort the keys (for example, to update a chart data)
let newMap = new Map([...map.entries()].sort())
let keys = Array.from(newMap.keys()) // ['a','b','d']
let values = Array.from(newMap.values()) // [5,12,6]
I have a dictionary of prices and quantities. I am getting updates on the price and values multiple times in a second so I don't want to store them in an array because dictionary are much faster.
let mainPriceValDict = [Double:Double]()
The data is coming in as an array of JSON so I am using codable to parse the JSON and put it into a dictionary. When I use the data, it needs to be sorted in ascending and/or descending order because I am looping through each price in order to get to a certain total quantity. The format that the array is in that I am looping through is as follows:
let loopingArray = [PriceQuantityEntry]()
struct PriceQuantityEntry {
let price : Double
let size : Double
}
I want to sort the prices which are the keys in the dictionary above and convert them into an array of PriceQuantityEntry. What is the best way to do this? In ascending and deciding order. I have tried first getting all the keys sorted and then grabbing associated values and putting them into the array in order but this seems like more processing than this task actually requires.
I think the best way to do this would be to put a custom initializer in the struct to convert the dictionary value to a value of type PriceQuantityEntry but I am not exactly sure how that would work with the sorting.
This is what I am currently doing to get it to work. I just feel like there is a more efficient way for it to be done. If you feel like I should keep the structure as an array instead of converting it to a dict, let me know.
loopingArray = self.mainPriceValDict.sorted { $0.0 < $1.0 }.map { PriceQuantityEntry(price: $0.0, size: $0.1) }
If you are getting a lot of updates to individual entries, both a dictionary and an array may cause memory copies of the whole memory structure every time an entry is changed.
I would suggest using objects (classes) instead of structures. This will allow you to use both an array and a dictionary to reference the object instances. The dictionary will provide direct access for updates and the array will allow sequential processing in forward or backward order.
[EDIT] Example:
class PriceQuantityEntry
{
static var all:[PriceQuantityEntry] = []
static var prices:[Double:PriceQuantityEntry] = [:]
var price : Double
var size : Double
init(price:Double, size:Double)
{
self.price = price
self.size = size
PriceQuantityEntry.all.append(self)
// PriceQuantityEntry.all.resort() // on demand or when new prices added
PriceQuantityEntry.prices[price] = self
}
class func update(price:Double, with size:Double)
{
if let instance = PriceQuantityEntry.prices[price]
{ instance.size = size }
else
{
let _ = PriceQuantityEntry(price:price, size:size)
PriceQuantityEntry.resort()
}
}
class func resort()
{
PriceQuantityEntry.all.sort{$0.price < $1.price}
}
}
// if adding multiple initial entries before updates ...
let _ = PriceQuantityEntry(price:1, size:3)
let _ = PriceQuantityEntry(price:1.25, size:2)
let _ = PriceQuantityEntry(price:0.95, size:1)
PriceQuantityEntry.resort()
// for updates ...
PriceQuantityEntry.update(price:1, with: 2)
// going throug list ...
var count:Double = 0
var total:Double = 0
var quantity:Double = 5
for entry in PriceQuantityEntry.all
{
total += min(entry.size,quantity-count) * entry.price
count = min(quantity,count + entry.size)
if count == quantity {break}
}
I'm new to Swift. I can read data (many rows and columns of names and mailing addresses) from csv file format. I have several of these files, so I created a function just to read the files and extract the data into a multidimensional array(s) - names, addresses, city, state, country. I read each of the lines from the file and try to append it to multidimensional array but I get errors - either index out of range or file type mismatch. What's the best way to enable this. See code below.
func getMailing(fileName: String) -> ([[String]])? {
let totalList = 243
var tempList: [String] = []
var arrayList = [[String]]()
guard let path = Bundle.main.url(forResource: fileName, withExtension: "csv") else {
print("File Error")
arrayList = [[""]]
return (arrayList)
}
do {
// get mailing data from file
let content = try String(contentsOf:path, encoding: String.Encoding.utf8)
// separate each line entry
tempList = content.components(separatedBy: "\r\n")
for index in 0...totalList - 1 {
// get each line from list and post into an array
let singleLine = tempList[index].components(separatedBy: ",").dropFirst().prefix(5)
// store each line data into into a multidimensional array for easy retrieval
arrayList[index].append(singleLine)
}
}
return (arrayList)
} catch {
print("File Error")
arrayList = [[""]]
return (arrayList)
}
}
Based on the code you've shown, it looks like you're trying to change the values of two different empty arrays 243 times. You have a loop setup to iterate based on your totalList property, but where you got that value, I have no idea. It would be wise to determine that value programmatically if you can.
You're setting both tempList and arrayList as empty arrays:
var tempList: [String] = []
var arrayList = [[String]]()
But then you're going through a loop and trying to change the value of an entry that doesn't even exist, hence your index out of range error. You need to first add something to both these arrays, because right now they are empty. It's probably crashing the first time through the loop when you try to set singleLine to tempList[index].components(separatedBy: ",").dropFirst().prefix(5), because you're saying tempList[0].components(separatedBy: ",").dropFirst().prefix(5), while there isn't an entry for tempList at index 0 because it's still empty! If you're going to loop through an array, it's always wise to do it based on the count of the array, or at least a quick fix when you need to use an index from two different arrays:
// Get the maximum times you can iterate based on the lowest count from each array
let maxLoop = min(tempList.count - 1, arrayList.count - 1)
for index in 0...maxLoop {
// get each line from list and post into an array
let singleLine = tempList[index].components(separatedBy: ",").dropFirst().prefix(5)
// store each line data into into a multidimensional array for easy retrieval
arrayList[index].append(singleLine)
}
Now that little chunk of code above won't even go through the loop once, because both arrays are still empty. You need to somewhere take your mailing data and parse it so that you can populate tempList and arrayList
For my project, I extracted tweets from a CSV file in Swift. Problem is now all tweets are parsed as one element in an array, separated by ",".
let tweetsOfColumns = columns["tweet"]
let seperatedColumns = tweetsOfColumns.componentsSeparatedByString(",")
Error message: '[String]?' does not have a member named
'componentsSeparatedByString'.
I checked if tweetsOfColumns contains multiple elements, but it doesn't allow me to subscript with tweetsOfColumns[index].
Looking at the link you reference, columns["tweets"] is going to give you back an array of the values from the "tweets" column, so it's what you need already, there's no additional comma's to split things on, you just need:
let seperatedColumns = columns["tweet"]
to have an array containing the tweet column for each row.
When you try to get an element from a dictionary, like
columns["tweet"]
it will give you back an optional, because if there is nothing associated with the key, it gives you back nil (None), otherwise the value wrapped in an optional (Some(data)).
So you have to unwrap the optional for example:
columns["tweet"]!
You have to either use the optional ? to access the string:
let seperatedColumns = tweetsOfColumns?.componentsSeparatedByString(",")
But you should unwrap it:
if let unwrappedTweets = tweetsOfColumns?.componentsSeparatedByString(","){
let seperatedColumns = unwrappedTweets
}
The problem is probably that you'll get an optional back, which you have to unwrap. And the easiest and most elegant is to use the if-let unwrapper.
if let tweetsOfColumns = columns["tweet"] {
let seperatedColumns = tweetsOfColumns.componentsSeparatedByString(",")
// do something with the seperatedColumns
}
Based on David's question and the OP's response in the OP comments, you can use map on the Array returned by columns["tweet"]. Please post actual data/code in the future.
let columns = [
"tweet":["handleX,tag1,tag2,textA,textB",
"handleY,tag1,tag2,textC,textD"]]
var chunk = [[String]]()
if columns["tweet"] != nil {
chunk = columns["tweet"]!.map {
return $0.componentsSeparatedByString(",")
}
}
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