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Swift: iterate using Index and Element


Swift: iterate using Index and Element

By : user2950099
Date : November 17 2020, 11:52 AM
it helps some times As Airspeed Velocity notes, I assume you mean enumerate here rather than generate. The tool you want, however, is indices to get all the indices of the collection:
code :
func find<C : CollectionType>(domain: C, comparator: (C.Generator.Element) -> Bool) -> C.Index? {
    for index in indices(domain) {
        if comparator(domain[index]) {
            return index
        }
    }    
    return nil
}


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Index and Iterate over CollectionType in swift

Index and Iterate over CollectionType in swift


By : James Curtin
Date : March 29 2020, 07:55 AM
Any of those help I have code which is basically like this: , You can restrict the method to collections which are indexed by Int:
code :
func arrayHalvesEqual<ByteArray : CollectionType where ByteArray.Index == Int, ByteArray.Generator.Element == UInt8>
    (data:ByteArray) -> Bool { ... }
func arrayHalvesEqual<ByteArray : CollectionType where ByteArray.Index : IntegerType, ByteArray.SubSequence.Generator.Element : Equatable>
    (data:ByteArray) -> Bool {

        let midPoint = (data.indices.endIndex - data.indices.startIndex)/2
        let firstHalf = data[data.indices.startIndex ..< midPoint]
        let secondHalf = data[midPoint ..< data.indices.endIndex]
        return !zip(firstHalf, secondHalf).contains { $0 != $1 }
}
A correct and idiomatic way to iterate through a collection with index in Swift?

A correct and idiomatic way to iterate through a collection with index in Swift?


By : John
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further For any collection the indices property returns a range of the valid indices. To iterate over the indices and the corresponding elements in parallel you can use zip():
code :
for (idx, el) in zip(collection.indices, collection) {
    print(idx, el)
}
let a = ["a", "b", "c", "d", "e", "f"]
let slice = a[2 ..< 5]

for (idx, el) in zip(slice.indices, slice) {
    print("element at \(idx) is \(el)")
}
element at 2 is c
element at 3 is d
element at 4 is e
// Swift 2:
extension CollectionType {
    func indexEnumerate() -> AnySequence<(index: Index, element: Generator.Element)> {
        return AnySequence(zip(indices, self))
    }
}

// Swift 3:
extension Collection {
    func indexEnumerate() -> AnySequence<(Indices.Iterator.Element, Iterator.Element)> {
        return AnySequence(zip(indices, self))
    }
}
let chars = "az".characters
for (idx, el) in chars.indexEnumerate() {
    print("element at \(idx) is \(el)")
}
element at 0 is a
element at 1 is 
element at 3 is 
element at 7 is z
Swift 3.0 iterate over String.Index range

Swift 3.0 iterate over String.Index range


By : Justin
Date : March 29 2020, 07:55 AM
Any of those help You can traverse a string by using indices property of the characters property like this:
code :
let letters = "string"
let middle = letters.index(letters.startIndex, offsetBy: letters.characters.count / 2)

for index in letters.characters.indices {

    // to traverse to half the length of string 
    if index == middle { break }  // s, t, r

    print(letters[index])  // s, t, r, i, n, g
}
let secondChar = letters[1] 
// error: subscript is unavailable, cannot subscript String with an Int
Iterate an array with index in Swift 3

Iterate an array with index in Swift 3


By : Zaman03
Date : March 29 2020, 07:55 AM
this one helps. You forgot to call a.enumerated(), which is what gives you the (index, value) tuples. for value in a is what gives you each element without the index.
Swift: For Loop to iterate through enumerated array by index greater than 1

Swift: For Loop to iterate through enumerated array by index greater than 1


By : babi chan
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Is there a way to use a for-in loop through an array of strings by an index greater than 1 using .enumerated() and stride, in order to keep the index and the value? , You have two ways to get your desired output.
code :
var testArray2: [String] = ["a", "b", "c", "d", "e"]

for index in stride(from: 0, to: testArray2.count, by: 2) {
    print("position \(index) : \(testArray2[index])")
}
for (index,item) in testArray2.enumerated() where index % 2 == 0 {
    print("position \(index) : \(item)")
}
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