My code does not work right now. I am trying to take names and add it by itself in the loop but the complier is giving me a error message and the code is not being printed.
let names = [Double(2),3,8] as [Any]
let count = names.count
for i in 0..<count {
print((names[i]) + names[i])
}
Because Any doesn't have + operator.
This will give you the result you expected.
If you want to add 2 values and print the result, you need to cast Any to calculatable like Double
let names = [Double(2),3,8] as [Any]
let count = names.count
for i in 0..<count {
if let value = names[i] as? Double {
print(value + value)
}
}
The use of as [Any] makes no sense. You can't add two objects of type Any which is probably what your error is about.
Simply drop it and your code works.
let names = [Double(2),3,8]
let count = names.count
for i in 0..<count {
print(names[i] + names[i])
}
Output:
4.0
6.0
16.0
Better yet:
let names = [Double(2),3,8]
for num in names {
print(num + num)
}
Related
I have these two functions:
func search_DocumentMultimedia(documentId: Int) -> Array<Int>{
var array:[Int]
let downloadUrl = FileManager.default.urls(for:.downloadsDirectory, in: .userDomainMask)[0]
let path = downloadUrl.appendingPathComponent("mwb_" + language + "_" + issue + ".db")
do{
let db = try Connection(path.absoluteString)
let documentMultimediaTable = Table("DocumentMultimedia")
let documentMultimediaIdField = Expression<Int>("DocumentMultimediaId")
let documentIdField = Expression<Int>("DocumentId")
for media in try db.prepare(documentMultimediaTable.select(documentMultimediaIdField, documentIdField).where(documentIdField == documentId)) {
array.append(media[documentMultimediaIdField])
}
} catch{
print(error)
}
return array
}
func search_Multimedia(multimediaID: [Int]) -> Array<mediaData>{
var array:[mediaData]
let downloadUrl = FileManager.default.urls(for:.downloadsDirectory, in: .userDomainMask)[0]
let path = downloadUrl.appendingPathComponent("mwb_" + language + "_" + issue + ".db")
ForEach(0..<multimediaID.count, id: \.self) { index in
do{
let db = try Connection(path.absoluteString)
let documentMultimediaTable = Table("Multimedia")
let MultimediaIdField = Expression<Int>("MultimediaId")
let keySymbol = Expression<String>("KeySymbol")
let track = Expression<Int>("Track")
let issueTagNumber = Expression<Int>("IssueTagNumber")
let mimeType = Expression<String>("MimeType")
let filePath = Expression<String>("FilePath")
for media in try db.prepare(documentMultimediaTable.select(MultimediaIdField, keySymbol, track, issueTagNumber, mimeType, filePath).where(MultimediaIdField == multimediaID[index])) {
let data = mediaData(mediaID: media[MultimediaIdField], mediaType: media[keySymbol], track: media[track], issueTagNumber: media[issueTagNumber], mimeType: media[mimeType], filePath: media[filePath])
array.append(data)
}
} catch{
print(error)
}
}
return array
}
I call them like this:
func getMedia(documentId: Int, nextDocumentId: Int) /*-> Array<videoData>*/ {
let multimediaId:[Int] = JW.search_DocumentMultimedia(documentId: documentId)
let mediaData:[mediaData] = JW.search_Multimedia(multimediaID: multimediaId)
print(mediaData)
}
In search_Multimedia I keep getting an error that says 'Ambiguous reference to member 'count''. I get this error on ForEach statement that uses multimediaID.count. I have tried everything but can't find how to resolve this. Please could you lend a hand? I saw a similar question on here but it seems to be outdated - hence my post.
You are using ForEach where ForEach is not appropriate. The purpose of ForEach is to turn a collection of values into a collection of SwiftUI Views inside the body of some collection view like a List or a VStack.
You don't need to create a collection of Views here. Use a regular Swift for/in statement. Replace this:
ForEach(0..<multimediaID.count, id: \.self) { index in
with this:
for index in 0 ..< multimediaID.count {
I think you have other errors, but this one is particularly important. ForEach (like most SwiftUI types) relies heavily on type inference. Mistakes in a ForEach call can seriously confuse the Swift compiler's type inference implementation. Then the compiler often prints useless or misleading error messages. So if you replace your ForEach with for/in loop, the compiler will probably give you better messages about any other errors you have made in this code.
I am stuck at a problem which i am trying to figure out in Swift 4.
Let say, i have the below variables
let var1 = "One"
let var2 = "Two"
let var3 = "Three"
var counter = 1
// Loop Start
let currentVariable = "var" + "\(counter)"
//Fetch the value of variable stored under currentVariable
counter += 1
//Loop end
I am trying to get the value based on variable name stored under currentVariable.
You can set up dictionary, replacing your variable names with keys.
let letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
var myDictionary:[String:String] = ["var1":"One", "var2":"Two", "varA":"A", "varB":"B"] // note, both sides can be different types than String
for x in 0...9 {
let myKey = "var" + String(x)
printValue(myKey)
}
for x in letters.characters {
let myKey = "var" + String(x)
printValue(myKey)
}
The simple function:
func printValue(_ key:String) {
let myValue = myDictionary[key]
if myValue != nil {
print(myValue)
}
}
I'm pretty sure you can make things a bit more elegant, but you get the idea. Also, keep in mind that a Dictionary is "unordered", as opposed to an array.
Use an array
let myArray = ["one", "two", "three"];
var counter = 1;
print(myArray[counter]);
I have a string of binary values e.g. "010010000110010101111001". Is there a simple way to convert this string into its ascii representation to get (in this case) "Hey"?
Only found the other way or things for Integer:
let binary = "11001"
if let number = Int(binary, radix: 2) {
print(number) // Output: 25
}
Do someone know a good and efficient solution for this case?
A variant of #OOPer's solution would be to use a conditionally binding while loop and index(_:offsetBy:limitedBy:) in order to iterate over the 8 character substrings, taking advantage of the fact that index(_:offsetBy:limitedBy:) returns nil when you try to advance past the limit.
let binaryBits = "010010000110010101111001"
var result = ""
var index = binaryBits.startIndex
while let next = binaryBits.index(index, offsetBy: 8, limitedBy: binaryBits.endIndex) {
let asciiCode = UInt8(binaryBits[index..<next], radix: 2)!
result.append(Character(UnicodeScalar(asciiCode)))
index = next
}
print(result) // Hey
Note that we're going via Character rather than String in the intermediate step – this is simply to take advantage of the fact that Character is specially optimised for cases where the UTF-8 representation fits into 63 bytes, which is the case here. This saves heap-allocating an intermediate buffer for each character.
Purely for the fun of it, another approach could be to use sequence(state:next:) in order to create a sequence of the start and end indices of each substring, and then reduce in order to concatenate the resultant characters together into a string:
let binaryBits = "010010000110010101111001"
// returns a lazily evaluated sequence of the start and end indices for each substring
// of 8 characters.
let indices = sequence(state: binaryBits.startIndex, next: {
index -> (index: String.Index, nextIndex: String.Index)? in
let previousIndex = index
// Advance the current index – if it didn't go past the limit, then return the
// current index along with the advanced index as a new element of the sequence.
return binaryBits.characters.formIndex(&index, offsetBy: 8, limitedBy: binaryBits.endIndex) ? (previousIndex, index) : nil
})
// iterate over the indices, concatenating the resultant characters together.
let result = indices.reduce("") {
$0 + String(UnicodeScalar(UInt8(binaryBits[$1.index..<$1.nextIndex], radix: 2)!))
}
print(result) // Hey
On the face of it, this appears to be much less efficient than the first solution (due to the fact that reduce should copy the string at each iteration) – however it appears the compiler is able to perform some optimisations to make it not much slower than the first solution.
You may need to split the input binary digits into 8-bit chunks, and then convert each chunk to an ASCII character. I cannot think of a super simple way:
var binaryBits = "010010000110010101111001"
var index = binaryBits.startIndex
var result: String = ""
for _ in 0..<binaryBits.characters.count/8 {
let nextIndex = binaryBits.index(index, offsetBy: 8)
let charBits = binaryBits[index..<nextIndex]
result += String(UnicodeScalar(UInt8(charBits, radix: 2)!))
index = nextIndex
}
print(result) //->Hey
Does basically the same as OOPer's solution, but he/she was faster and has a shorter, more elegant approach :-)
func getASCIIString(from binaryString: String) -> String? {
guard binaryString.characters.count % 8 == 0 else {
return nil
}
var asciiCharacters = [String]()
var asciiString = ""
let startIndex = binaryString.startIndex
var currentLowerIndex = startIndex
while currentLowerIndex < binaryString.endIndex {
let currentUpperIndex = binaryString.index(currentLowerIndex, offsetBy: 8)
let character = binaryString.substring(with: Range(uncheckedBounds: (lower: currentLowerIndex, upper: currentUpperIndex)))
asciiCharacters.append(character)
currentLowerIndex = currentUpperIndex
}
for asciiChar in asciiCharacters {
if let number = UInt8(asciiChar, radix: 2) {
let character = String(describing: UnicodeScalar(number))
asciiString.append(character)
} else {
return nil
}
}
return asciiString
}
let binaryString = "010010000110010101111001"
if let asciiString = getASCIIString(from: binaryString) {
print(asciiString) // Hey
}
A different approach
let bytes_string: String = "010010000110010101111001"
var range_count: Int = 0
let characters_array: [String] = Array(bytes_string.characters).map({ String($0)})
var conversion: String = ""
repeat
{
let sub_range = characters_array[range_count ..< (range_count + 8)]
let sub_string: String = sub_range.reduce("") { $0 + $1 }
let character: String = String(UnicodeScalar(UInt8(sub_string, radix: 2)!))
conversion += character
range_count += 8
} while range_count < characters_array.count
print(conversion)
You can do this:
extension String {
var binaryToAscii: String {
stride(from: 0, through: count - 1, by: 8)
.map { i in map { String($0)}[i..<(i + 8)].joined() }
.map { String(UnicodeScalar(UInt8($0, radix: 2)!)) }
.joined()
}
}
I have a block that updates the view for each String. In its object class I pass it by:
func eachFeaturesSection(block: ((String?) -> Void)?) {
propertyFeatures.forEach { feature in
guard let feature = feature as? RealmString else {
return
}
let features = feature.stringValue
block?(features)
}
}
and I will get it in ViewController, by:
listing!.eachFeaturesSection({ (features) in
print(features)
self.facilities = features!
})
So it will print as:
Optional("String 1")
Optional("String 2")
and self.facilities will be set to latest value which is self.facilities = "String 2"
cell.features.text = features // it will print String 2
So, how can I achieve to join all strings together in one string such as self.facilities = "String 1, String 2". I used .jointString does not work. Thank you for any help.
Maybe you could add them to an array of String elements and then, when done, call joined on that array.
So something like this in your ViewController:
var featuresArray = [String]()
listing!.eachFeaturesSectionT({ (features) in
print(features)
featuresArray.append(features!)
})
//Swift 3 syntax
cell.features.text = featuresArray.joined(separator: ", ")
//Swift 2 syntax
cell.features.text = featuresArray.joinWithSeparator(", ")
Hope that helps you.
self.facilities = features! is doing nothing but keeps updating the value every iteration
Change the line self.facilities = features! to self.facilities += features! or self.facilities = self.facilities + ", " + features!
Here's how I'd do it (assuming your propertyFeatures is an array of RealmString):
Swift 3:
let string = (propertyFeatures.map { $0.stringValue }).joined(separator: ", ")
Swift 2:
let string = (propertyFeatures.map { $0.stringValue }).joinWithSeparator(", ")
Using Swift, I'm trying to take a list of numbers input in a text view in an app and create a sum of this list by extracting each number for a grade calculator. Also the amount of values put in by the user changes each time. An example is shown below:
String of: 98,99,97,96...
Trying to get: 98+99+97+96...
Please Help!
Thanks
Use components(separatedBy:) to break up the comma-separated string.
Use trimmingCharacters(in:) to remove spaces before and after each element
Use Int() to convert each element into an integer.
Use compactMap (previously called flatMap) to remove any items that couldn't be converted to Int.
Use reduce to sum up the array of Int.
let input = " 98 ,99 , 97, 96 "
let values = input.components(separatedBy: ",").compactMap { Int($0.trimmingCharacters(in: .whitespaces)) }
let sum = values.reduce(0, +)
print(sum) // 390
For Swift 3 and Swift 4.
Simple way: Hard coded. Only useful if you know the exact amount of integers coming up, wanting to get calculated and printed/used further on.
let string98: String = "98"
let string99: String = "99"
let string100: String = "100"
let string101: String = "101"
let int98: Int = Int(string98)!
let int99: Int = Int(string99)!
let int100: Int = Int(string100)!
let int101: Int = Int(string101)!
// optional chaining (if or guard) instead of "!" recommended. therefore option b is better
let finalInt: Int = int98 + int99 + int100 + int101
print(finalInt) // prints Optional(398) (optional)
Fancy way as a function: Generic way. Here you can put as many strings in as you need in the end. You could, for example, gather all the strings first and then use the array to have them calculated.
func getCalculatedIntegerFrom(strings: [String]) -> Int {
var result = Int()
for element in strings {
guard let int = Int(element) else {
break // or return nil
// break instead of return, returns Integer of all
// the values it was able to turn into Integer
// so even if there is a String f.e. "123S", it would
// still return an Integer instead of nil
// if you want to use return, you have to set "-> Int?" as optional
}
result = result + int
}
return result
}
let arrayOfStrings = ["98", "99", "100", "101"]
let result = getCalculatedIntegerFrom(strings: arrayOfStrings)
print(result) // prints 398 (non-optional)
let myString = "556"
let myInt = Int(myString)