How can you remove a specific object from an Array of string.
array = ["mac","iPhone","iPad"]
Is there a method to delete a specific string in the array, like for example i wanted to remove "iPhone", without using removeAtIndex(1)
Use filter for that purpose
var array = ["mac","iPhone","iPad"]
array = array.filter() { $0 != "mac" }
print(array) // will print ["iPhone", "iPad"]
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 struct array that i want "break up" into smaller arrays that can be called as needed or at least figure out how i can map the items needed off one text value.
the struct:
struct CollectionStruct {
var name : String
var description : String
var title : String
var image : PFFile
var id: String
}
and the array made from the struct
var collectionArray = [CollectionStruct]()
var i = 0
for item in collectionArray {
print(collectionArray[i].name)
i += 1
}
printing partArray[i].name gives the following result:
pk00_pt01
pk00_pt02
pk00_pt03
pk01_pt01
pk01_pt02
pk01_pt03
pk01_pt04
pk01_pt05
pk01_pt06
pk01_pt07
pk01_pt08
this is just some test values but there could be thousands of entries here so i wanted to filter the entire array just by the first 4 characters of [i].name i can achieve this by looping through as above but is this achievable using something like .map?
I wanted to filter the entire array just by the first 4 characters of
[i].name
You can achieve this by filtering the array based on the substring value of the name, as follows:
let filteredArray = collectionArray.filter {
$0.name.substring(to: $0.name.index($0.name.startIndex, offsetBy: 4)).lowercased() == "pk00"
// or instead of "pk00", add the first 4 characters you want to compare
}
filteredArray will be filled based on what is the compared string.
Hope this helped.
If you want to group all data automatically by their name prefix. You could use a reducer to generate a dictionary of grouped items. Something like this:
let groupedData = array.reduce([String: [String]]()) { (dictionary, myStruct) in
let grouper = myStruct.name.substring(to: myStruct.name.index(myStruct.name.startIndex, offsetBy: 4))
var newDictionart = dictionary
if let collectionStructs = newDictionart[grouper] {
newDictionart[grouper] = collectionStructs + [myStruct.name]
} else {
newDictionart[grouper] = [myStruct.name]
}
return newDictionart
}
This will produce a dictionary like this:
[
"pk00": ["pk00_pt01", "pk00_pt02", "pk00_pt03"],
"pk01": ["pk01_pt01", "pk01_pt02", "pk01_pt03", "pk01_pt04", "pk01_pt05", "pk01_pt06", "pk01_pt07"],
"pk02": ["pk02_pt08"]
]
Not sure if i am understanding you correctly but it sounds like you are looking for this...
To create a new array named partArray from an already existing array named collectionArray (that is of type CollectionStruct) you would do...
var partArray = collectionArray.map{$0.name}
Goal: I have two different classes, and two arrays containing members of each class. Using Swift 2.0, I would like to find the unique members of one array compared to the other based on specific attributes of each class.
Example:
class A {
var name: String
init(name: String) {
self.name = name
}
}
class B {
var title: String
init(title: String) {
self.title = title
}
}
let aArray = [A(name:"1"), A(name:"2"), A(name:"3"), A(name:"4")]
let bArray = [B(title:"1"), B(title:"2"), B(title:"5")]
So, I'm looking for some operation between aArray and bArray which returns the 3rd and 4th element of aArray, because they are uniquely in aArray, where the basis of comparison is the attributes A.name and B.title.
Of course, reversing the order of the operation would pick out the 3rd element of bArray, because it is uniquely in bArray.
I know I can accomplish the goal straightforwardly using a simple for loop, but I was hoping for something more elegant and more optimized. But if a for loop is as fast or faster than anything fancier, I'm happy to use it just as well.
I'm not sure fancy or elegant this code is, but, we could do something like this:
let mappedArray = bArray.map { $0.title }
let filteredArray = aArray.filter { !mappedArray.contains($0.name) }
So when we want the unique elements from aArray, we first map the elements from bArray to get an array of the value we want to actually compare:
let mappedArray = bArray.map { $0.title }
mappedArray is just an array of strings based on the title property of the objects in bArray.
Next, we use the filter method to filter objects from aArray. The filter method returns an array with objects that pass the test in our closure. The test we want to apply is objects that are not contained in the mapped array we just built.
let filteredArray = aArray.filter { !mappedArray.contains($0.name) }
If we want to do it the other way, just change a few things:
let mappedArray = aArray.map { $0.name }
let filteredArray = bArray.filter { !mappedArray.contains($0.title) }
A simple question but a big problem with the Apple Watch.
I am searching the index of an element in an Array. But the code gives me nil.
override func awakeWithContext(context: AnyObject?) {
super.awakeWithContext(context)
let temperatur = context as! String
let SliderData = ["off", "comfort", "eco","5.0", "5.5", "6.0", "6.5"]
println(toString(temperatur.dynamicType))
println(find(SliderData, "\(temperatur)") )
}
The array does not contain the string contained in the variable "temperatur" which is why you are not getting an index back.
If the value is already a string then you don't need to use "\(temperatur)" You can use this line instead:
println(find(SliderData, temperatur) )
You're searching for the string "temperatur" – which is obviously not in the array – rather than for the content of the variable temperatur
println(find(SliderData, temperatur) )
I am trying to create a array to hold dictionaries.
var deaultScoreResults : [Dictionary<String, Int>] = [];
But when I try to add a dictionary key:value pair I get:
deaultScoreResults.append(["Study Up!", 1]);
Error;
Type 'Dictionary' does not conform to protocol
'ArrayLiteralConvertible'
Square brackets surrounding a comma separated list of values is an array literal.
["this", "is", "a", "swift", "literal", "array"]
For a literal dictionary, you need a comma separated list of key:value pairs:
[1:"this", 2:"is", 3:"a", 4:"swift", 5:"literal", 6:"dictionary"]
To fix the error, you simply need to change your comma to a colon:
defaultScoreResults.append(["Study Up!":1])
However, based on your previous question, I'm going to assume an array of <String, Int> dictionaries isn't anywhere near what you're looking for.
I would suggest that you want simply an <Int, String> dictionary:
var defaultScoreResults = Dictionary<Int, String>()
defaultScoreResults[1] = "Study Up!"
Try this:
var deaultScoreResults = [Dictionary<String, Int>]()
deaultScoreResults.append(["Study Up!":1])
You could also declare it like this:
var deaultScoreResults = [[String:Int]]()