CODEWITHSUNDEEP
arraysswiftdictionary
BadmintonCat
BadmintonCat

Reputation: 9586

Apply Array.map with Dictionary

How would I write the following code correctly in Swift 4.2:

let navStack = ["root", "page1", "page3"]
let route = ["root", "page1", "page2", "page3"]
let routeTags =
[
    "root": ["root"],
    "page1": ["page1", "page2"],
    "page3": ["page3"]
]
let r = navStack.map({ routeTags[$0] }).joined(separator: "/")

The current code doesn't compile (ambiguous reference to member 'subscript'). The code should produce a string with the dictionary values mapped according to the keys in navStack.

Upvotes: 0

Views: 66

Answers (1)

vadian
vadian

Reputation: 285290

Two issues:

  1. The result of routeTags[$0] is an optional and must be unwrapped (safely with compactMap).
  2. The joined expression must be moved into the closure because the second item is an array.
let navStack = ["root", "page1", "page3"]
let route = ["root", "page1", "page2", "page3"]
let routeTags =
    [
        "root": ["root"],
        "page1": ["page1", "page2"],
        "page3": ["page3"]
]
let r = navStack.compactMap{ routeTags[$0]?.joined(separator: "/") }

Or you have to use joined twice if you want one single string:

let r = navStack.compactMap{ routeTags[$0]?.joined(separator: "/") }.joined(separator: "/")

Upvotes: 1

Related Questions