Unable to .append to an array of structs

I have created a Book struct with author and title defined. I then declare a var as an array of Book. I then declare several instances of Book. None of which generates any errors.

However, when I try to .append my Book instances to my array of Book it fails.

The problem is here:

myBooks.append(mb1)

Here is my code:

import SwiftUI

struct ContentView: View {
   
   var myBooks: [Book] = []
   
   let mb1 = Book(title: "Lies", author: "Franken, Al")
   let mb2 = Book(title: "Road to Hell, The", author: "Groening, Matt")
   let mb3 = Book(title: "Our Dumb Century", author: "the ONION")
   
   myBooks.append(mb1)
   
   var body: some View {
   
      VStack(alignment: .leading) {
         BookRow(book: mb1)
         BookRow(book: mb2)
         BookRow(book: mb3)
      }
      .padding()
   }
}

#Preview {
   ContentView()
}

Here is my struct:

struct Book {
   let title: String
   let author: String
   
   init(title: String = "Hercules", author: String = "Author") {
      self.title = title
      self.author = author
   }
}

The remainder of my code (but I don’t think it is relevant):

import SwiftUI

extension Book {
   struct Image: View {
      
      let title: String
      
      var body: some View {
         
         let symbol =
         SwiftUI.Image(title: title)
         ?? .init(systemName: "book")
         
         symbol
            .resizable()
            .scaledToFit()
            .frame(width: 80, height: 80)
            .font(Font.title.weight(.light))
            .foregroundColor(.secondary.opacity(0.5))
      }
   }
}

extension Image {
   
   init?(title: String) {
      guard let character = title.first,
            case let symbolName = "\(character.lowercased()).square",
            UIImage(systemName: symbolName) != nil
      else {
         return nil
      }
      
      self.init(systemName: symbolName)
      
   }
}


struct BookRow: View {
   
   let book: Book
   
   var body: some View {
      HStack {
         Book.Image(title: book.title)
         VStack(alignment: .leading) {
            Text("\(book.title)")
            Text("\(book.author)")
               .foregroundColor(.secondary)
         }
         .font(.title2)
      }
   }
}

>Solution :

The main problem here is that you have added executing code in places where there should be only declarations.

struct ContentView: View {
   
   var myBooks: [Book] = []
   
   let mb1 = Book(title: "Lies", author: "Franken, Al")
   let mb2 = Book(title: "Road to Hell, The", author: "Groening, Matt")
   let mb3 = Book(title: "Our Dumb Century", author: "the ONION")
   
   myBooks.append(mb1)

You can’t call append here since, you need to be inside a method to do that. (I guess also mb1, mb2 and mb3 are misplaced).

Two options, either add an init and build up your array there

init() {
    myBooks.append(Book(title: "Lies", author: "Franken, Al"))
    myBooks.append(Book(title: "Road to Hell, The", author: "Groening, Matt"))
    myBooks.append(Book(title: "Our Dumb Century", author: "the ONION"))
}

Or you could include it in the declaration of the array

var myBooks: [Book] = [ 
    Book(title: "Lies", author: "Franken, Al"),
    Book(title: "Road to Hell, The", author: "Groening, Matt"),
    Book(title: "Our Dumb Century", author: "the ONION")
]

And since we now only have an array the view code in body changes to

List(myBooks, id: \.title) { book in
    BookRow(book: book)
}