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iOS Build a Simple iPhone App with Swift Getting Started with iOS Development Swift Recap Part 1

Posted by Florian Lindorfer
Florian Lindorfer
16,415 Points

What's the problem with converting from Tag to String?

When I want to indicate self.tag within the description() function, I get an error: __lldb_expr_175.Post in the debug area on the right side.

I can check it out with the eye symbol and the value is kind of wrapped.

I would say the error is somewhere at the init() method, trying to convert Tag to String!?

structs.swift 
struct Tag {
  let name: String
}

struct Post {
  let title: String
  let author: String
  let tag: Tag
  let description = 

  init(title: String, author: String, tag: String) {
    self.tag = tag
    self.title = title
    self.author = author  
  }
  func description() -> String {
    return "\(title) by \(author). Filed under \(tag)" 
  }
}

let firstPost = Post(title: "iOSDevelopment", author: "Apple", tag: "swift")
let postDescription = firstPost.description()

3 Answers

Steve Hunter
Steve Hunter
57,712 Points

Hi again,

Apologies, I just had cause to revisit this challenge for another student. I haven't done this updated course but had done the previous (two) incarnations for the Swift 1 & 2 iterations of the language.

In that, the init method was required and defining description happened within that method. In this one, it seems the init method isn't compulsory and the description is set within a func. So, while the corrections required were the same, the route to getting to the solution is slightly different than my recollections of the old course.

Apologies for the slight confusion.

Steve.

Florian Lindorfer
Florian Lindorfer
16,415 Points

Hi Steve,

As I worked with structs, the init method wasn't mandatory. So, the given struct Tag also had no init method. I was a bit confused, because I wasn't sure how to initialise the property of the "super" struct (Tag) in the "sub" struct (Post). Especially, how to deal with its regarding type. And you are right, I created a func description(). I interpolated title, author and tag.name in the return statement there.

Steve Hunter
Steve Hunter
57,712 Points

All good - as long as you got it sorted. I think in earlier iterations of Swift, the setting of stored properties was mandatory at initialisation. I'm pleased they've removed that requirement as it was a pain!!

Steve Hunter
Steve Hunter
57,712 Points

I think I'm mistaken - I'm confusing this with classes, perhaps? Anyway; I've stared at enough code of all languages for one week, I'm getting brain-fade - time for weekend to start!

Florian Lindorfer
Florian Lindorfer
16,415 Points

As far as I've learned, for classes the initialisation is mandatory, but I don't know if there are exceptions, I'm a total super newbie :)

Have a nice weekend :>

Steve Hunter
Steve Hunter
57,712 Points

I think you're right; classes require the init method. I've done so much code this week, I'm burned out! Time to rest & recover, i.e. go to the pub! :smile:

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi Florian,

The compiler tests are expecting to receive an instance of Tag when forming a Post object. You've sent it a string.

You can create a Tag by passing it a name:, which is a String. 

let tag = Tag(name: "Swift")

So, rather than assigning that into tag pass it as an argument into the Post creation.

You'll need to sort out your init method, but this is what the tests are expecting to receive:

let firstPost = Post(title: "iOSDevelopment", author: "Apple", tag: Tag(name: "swift"))

Also, the init method must assign a value to all stored properties so description needs a value setting too. You have the right idea for this but, again, the tag piece needs some work. It isn't a string (or shouldn't be!) so you can't interpolate it. You can interpolate its name property, though. So use dot notation on the instance of tag to add that into your string.

Let me know if that's enough or if should be more descriptive! I don't want to just give you the code but am happy to walk you through to a solution if that's what you're happier with.

Steve.

Florian Lindorfer
Florian Lindorfer
16,415 Points
Florian Lindorfer
Florian Lindorfer
16,415 Points

Hey Steve,

Awesome! I immediately solved the issue. Great syntax learning process in this case.

The problem was that I wanted to pass Tag(name:), or in the posted case a String, into the init method for initialising a tag. I tried some weird things with that type. Anyway, it's redundant because the name property / constant has already been created in the Tag struct. So, tag: Tag was enough to initialise it in the Post struct.

Thanks, for feeding my brain with pieces of mindset for the solution and not giving me the entire solution right away :)

Valuable help

Steve Hunter
Steve Hunter
57,712 Points

Glad you figured it out! :+1:

Steve.