Ray Toal Ray Toal - 4 months ago 23
iOS Question

Replacement for enumerateSubstringsInRange in Swift 3

I'm upgrading code from Swift 2 to Swift 3 and ran across this error:


wordcount.swift:7:5: error: value of type 'String' has no member 'enumerateSubstringsInRange'
line.enumerateSubstringsInRange(range, options: .ByWords) {w,,,_ in


In Swift 2, this method comes from a
String
extension of which the compiler is aware.

I have not been able to locate this method in the Swift 3 library. It appears in the documentation for
Foundation
here:

https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/index.html#//apple_ref/occ/instm/NSString/enumerateSubstringsInRange:options:usingBlock:

My entire script is:

import Foundation

var counts = [String: Int]()

while let line = readLine()?.lowercased() {
let range = line.characters.indices
line.enumerateSubstringsInRange(range, options: .ByWords) {w,_,_,_ in
guard let word = w else {return}
counts[word] = (counts[word] ?? 0) + 1
}
}

for (word, count) in (counts.sorted {$0.0 < $1.0}) {
print("\(word) \(count)")
}


It works with Swift 2.2 (modulo the changes I have already made for Swift 3, such as
lowercase
->
lowercased
and
sort
->
sorted
) but fails to compile with Swift 3.

And very strangely, neither the Swift 3 command line compiler nor the Swift Migration assistant in XCode 8 Beta suggests a replacement, as it does for many other renamed methods. Perhaps
enumerateSubstringsInRange
is deprecated or its parameter names changed?

Answer

If you type str.enumerateSubstrings in a Playground, you'll see the following as a completion option:

enumerateSubstrings(in: Range<Index>, options: EnumerationOptions, body: (substring: String?, substringRange: Range<Index>, enclosingRange: Range<Index>, inout Bool) -> ())

In addition to addressing the new enumerateSubstrings(in:options:body:) syntax, you need to also change how you get the range for the string:

import Foundation

var counts = [String: Int]()

while let line = readLine()?.lowercased() {
    let range = line.startIndex ..< line.endIndex
    line.enumerateSubstrings(in: range, options: .byWords) {w,_,_,_ in
        guard let word = w else {return}
        counts[word] = (counts[word] ?? 0) + 1
    }
}

for (word, count) in (counts.sorted {$0.0 < $1.0}) {
    print("\(word) \(count)")
}
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