Advanced Pattern Matching

Directory Traversion

released Fri, 15 Feb 2019
Swift Version 5.0

Directory Traversion

Imagine you want to traverse a file hierachy and find:

  • all "psd" files from customer1 and customer2
  • all "blend" files from customer2
  • all "jpeg" files from all customers.
guard let enumerator = FileManager.default.enumeratorAtPath("/customers/2014/")
    else { return }

for url in enumerator {
    switch (url.pathComponents, url.pathExtension) {

    // psd files from customer1, customer2
    case (let f, "psd") 
            where f.contains("customer1") || f.contains("customer2"): print(url)

    // blend files from customer2
    case (let f, "blend") 
            where f.contains("customer2"): print(url)

    // all jpg files
    case (_, "jpg"): print(url)

    default: ()

Note that contains stops at the first match and doesn't traverse the complete path. Again, pattern matching lead to very succinct and readable code.