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iOS Swift Collections and Control Flow Control Flow With Conditional Statements Working With Switch Statements

Manny Rothman
Manny Rothman
6,653 Points
Posted by Manny Rothman
Manny Rothman
6,653 Points

Help with Swift 3 switches

In the editor we have a dictionary that contains a three letter country code as a key and that country's capital city as the associated value.

We also have three empty arrays, europeanCapitals, asianCapitals, and otherCapitals. The goal is to iterate through the dictionary and end up with just the names of the capital cities in the relevant array.

For example, after you execute the code you write, europeanCapitals will have the values ["Vaduz", "Brussels", "Sofia"] (not necessarily in that order).

To do this you're going to use a switch statement and switch on the key. For cases where the key is a European country, append the value (not the key!) to the europeanCapitals array. For keys that are Asian countries, append the value to asianCapitals and finally for the default case, append the values to otherCapitals.

What am I doing wrong?

operators.swift 
var europeanCapitals: [String] = []
var asianCapitals: [String] = []
var otherCapitals: [String] = []

let world = [
  "BEL": "Brussels", 
  "LIE": "Vaduz", 
  "BGR": "Sofia", 
  "USA": "Washington D.C.", 
  "MEX": "Mexico City", 
  "BRA": "Brasilia", 
  "IND": "New Delhi", 
  "VNM": "Hanoi"]

for (key, value) in world {
    // Enter your code below
    switch world {
    case "BEL", "LIE", "BGR": var europeanCapitals.append("Brussels", "Vaduz", "Sofia")
    case "IND", "VNM": var asianCapitals.append("New Delhi", "Hanoi")
    default: var otherCapitals.append("Washington D.C.", "Mexico City", "Brasilia")
    }
    // End code
}
Abdullah Ahmad
Abdullah Ahmad
1,097 Points

I'm still new to coding as well so I apologize if this explanation is bad but you are on the right track from what I can see. The only things I see that should be corrected is, don't rewrite "var" because those variables have already been declared just call them by their name like "europeanCapitals", "asianCapitals" & "otherCapitals" NOT "var europeanCapitals" Also just call it asianCapitals.append(value) instead of listing the values there.

5 Answers

Marilyn Magnusen
Marilyn Magnusen
14,084 Points
Marilyn Magnusen
Marilyn Magnusen
14,084 Points 
    var europeanCapitals: [String] = []
    var asianCapitals: [String] = []
    var otherCapitals: [String] = []

let world = [
     "BEL": "Brussels", 
     "LIE": "Vaduz", 
     "BGR": "Sofia", 
     "USA": "Washington D.C.", 
     "MEX": "Mexico City", 
     "BRA": "Brasilia", 
      "IND": "New Delhi", 
      "VNM": "Hanoi"]

for (key, value) in world {
      // Enter your code below
     switch key {
     case "BEL", "LIE", "BGR": europeanCapitals.append(value)
     case "IND", "VNM": asianCapitals.append(value)
     default: otherCapitals.append(value)
     }
  // End code
}
          ```
Marilyn Magnusen
Marilyn Magnusen
14,084 Points
Marilyn Magnusen
Marilyn Magnusen
14,084 Points

This is my first time posting a reply, forgive the indentation.

These are the steps I took:

  1. the result of all this is that we want each of the arrays to store the relevant values, so europeanCapitals will have :Brussels, Vaduz, Sofia asianCapitals will have New Dehli, Hanoi, otherCapitals will have Washing DC, Mexico City, Brasilia

to do this

  1. the "for" statement has already been written out for us - leave this alone
  2. switch key (not value). The question specifically says "To do this you're going to use a switch statement and switch on the key"
  3. for the case, we can enter the keys in the array for example, "BEL" "LIE" "BGR"
  4. You don't need to explicitly write out the values as the compiler will compute this for us. But once the values are obtained, we do need to tell the compiler to append (add) these values to the relevant array. We do this using the .append method eg "europeanCapitals.append(value)"
Manny Rothman
Manny Rothman
6,653 Points
Manny Rothman
Manny Rothman
6,653 Points

Abdullah Ahmad , I updated my switch statement to be this:

    switch world {
    case "BEL", "LIE", "BGR": europeanCapitals.append(value)
    case "IND", "VNM": asianCapitals.append(value)
    default: otherCapitals.append(value)
    }

I'm still getting an error:

swift_lint.swift:23:10: error: expression pattern of type 'String' cannot match values of type '[String : String]'
    case "BEL", "LIE", "BGR": europeanCapitals.append(value)
         ^~~~~
swift_lint.swift:23:17: error: expression pattern of type 'String' cannot match values of type '[String : String]'
    case "BEL", "LIE", "BGR": europeanCapitals.append(value)
                ^~~~~
swift_lint.swift:23:24: error: expression pattern of type 'String' cannot match values of type '[String : String]'
    case "BEL", "LIE", "BGR": europeanCapitals.append(value)
                       ^~~~~
swift_lint.swift:24:10: error: expression pattern of type 'String' cannot match values of type '[String : String]'
    case "IND", "VNM": asianCapitals.append(value)
         ^~~~~
swift_lint.swift:24:17: error: expression pattern of type 'String' cannot match values of type '[String : String]'
    case "IND", "VNM": asianCapitals.append(value)
                ^~~~~
Abdullah Ahmad
Abdullah Ahmad
1,097 Points

It looks good but for your switch statement, we are switching for the "key" not "world so that should start like "switch key" not "switch world. Here's the way I did it if you wanna reference it. There are multiple ways to do it like he said in the video so yeah.

for (key, value) in world { switch key { case "BEL", "LTE", "BGR": europeanCapitals.append(value) case "IND", "VNM": asianCapitals.append(value) case "USA", "MEX", "BRA": otherCapitals.append(value) default:print("Not found") } }

Linus Karlsson
Linus Karlsson
7,402 Points

I am new to Swift.

How the h*** am I supposed to figure this out by myself after these few videos?!?

Should I feel stupid or should I blame the teacher in this case?

(Sorry for bad language)

Jens Aamand Øvig
Jens Aamand Øvig
1,776 Points
Jens Aamand Øvig
Jens Aamand Øvig
1,776 Points

Ive found that just typing it all works.. switch key { case "BEL": europeanCapitals.append("Brussels") case "LIE": europeanCapitals.append("Vaduz") case "BGR": europeanCapitals.append("Sofia") case "USA": otherCapitals.append("Washington D.C") case "Mex": otherCapitals.append("Mexico City") case "BRA": otherCapitals.append("Brasilia") case "IND": asianCapitals.append("New Delhi") default: asianCapitals.append("Hanoi") }}

Eddie Flickinger
Eddie Flickinger
3,513 Points
Eddie Flickinger
Eddie Flickinger
3,513 Points

I've literally had to lookup the last 3 or 4 solutions completely. The teachers voice is hard to listen to, but what he covers are relatively easy concepts. The problems are not. Should I be struggling this much?

Richard Then
Richard Then
10,690 Points
Richard Then
Richard Then
10,690 Points

for (key, value) in world {

switch key { case "BEL", "LIE", "BGR": europeanCapitals.append*(value)*

(key, value) is this standard when trying to refer to a key/value? and then switch key will only refer to halve of the contents in the parentheses(keys).

I didn't know that was even possible! I don't think Pasan went over this...

My coding was a mess trying to separate key/value ([String:String] to [String])!