How Use Use Swiftui Foreach with a Dictionary [ Customenum: Customstrut ] - Getting "Conform to 'Randomaccesscollection'" Error

How use use SwiftUI ForEach with a dictionary [ customEnum : customStrut ] - getting conform to 'RandomAccessCollection' error

As states dictionary is not "random access" capable collection, so it cannot be used directly in ForEach, here is possible approach

HStack {
    ForEach(Array(filterSelections.keys.enumerated()), id:\.element) { _, key in
        Text("TBD \(self.filterSelections[key]?.title ?? "")")
        // Will be putting checkboxes here - i.e. so can chose which ones
    }
}

Is it possible to iterate a dictionary inside ForEach in SwiftUI?

This is because a Dictionary is unordered. So its keys are unordered as well.

You need to make it ordered using Array:

ForEach(Array(viewModel.userDomains.keys).indices, id: \.self) { ...

As they are ordered randomly, you may also want to sort them:

ForEach(Array(viewModel.userDomains.keys).sorted().indices, id: \.self) { ...

But as the ordering and sorting gets more complex, you may think of moving the logic to the ViewModel instead.

[SwiftUI]: ForEach is not working for array of dictionary, dictionary with array

You can write it cleanly with

struct Model:Hashable {
    let type:String
    let unnits:[String]
}

struct ContentView: View {

    let arr_type2 = [Model(type:"Temperature", unnits: ["°C","°F","°K"])]

    var body: some View {
           ForEach(arr_type2, id: \.self) { item in

            Text(item.type)
        }
    }
}

For why check https://www.hackingwithswift.com/books/ios-swiftui/why-does-self-work-for-foreach

MapKit error when using AnnotatedItem in a ForEach

ForEach is for use inside a View hierarchy. You may be thinking of forEach, which can be used to perform loops on array elements, but it appears that what you actually want in this case is .map, which allows you to transform one array into another:

private var pointsOfInterest : [AnnotatedItem] {
  countries.map { country in 
    AnnotatedItem(name: country.display_name, coordinate: .init(latitude: country.latitude, longitude: country.longitude))
  }
}

Referencing initializer 'init(_:content:)' on 'ForEach' requires that 'Planet' conform to 'Identifiable'

ForEach needs to identify its contents in order to perform layout, successfully delegate gestures to child views and other tasks. Identifying the content means that there has to be some variable (which itself needs to conform to Hashable) that ForEach can use. In most cases, this is as simple as making your struct (Planet) conform to the Identifiable protocol. You did not provide implementation details of your Planets struct, but here is one way I could hink about that displays the point:

struct Planet: Identifiable {
    var id: String {
        self.name
    }
    var name: String
}

In this example, I'm assuming that the nam of a planet uniquely identifies it. Common ways of achieving this task are

Using UUID as identifier
Assigning a different integer (or using a static factory) to each new instance
Using an otherwise Hashable unique variable.

If you don't want to make your struct conform to Identifiable, you can also provide the variable you want this to be identified as as a key-path:

struct PlanetView: View {
    let planets: [Planet]

    var body: some View {
        ForEach(planets, id: \.name) { planet in
            //...
        }
    }
}

ForEach & indexof SwiftUI keep giving Closure containing control flow statement cannot be used with result builder 'TableRowBuilder'

ForEach is a View it isn't a for loop and you can't use \.self or use array.count, you have to supply a key that is a unique identifier for the data, or make your data struct implement Identifiable and have a let id set it from the JSON data.

How do you use .enumerated() with ForEach in SwiftUI?

TL;DR

Warning: If you get in the habit of using enumerated() with ForEach, you may one day end up with EXC_BAD_INSTRUCTION or Fatal error: Index out of bounds exceptions. This is because not all collections have 0-based indexes.

A better default is to use zip instead:

ForEach(Array(zip(items.indices, items)), id: \.0) { index, item in
  // index and item are both safe to use here
}

The folks over at Point-Free mentioned that it's not safe to rely on enumerated() with ForEach in production since not all collections are zero-index based:

This is technically not the most correct way to do this. It would be more correct, and more verbose, to zip the todos array with its indices collection. In this case we are safe because we are dealing with a simple 0-based index array, but if we were doing this in production we should probably zip-based approach.

Apple's documentation for the enumerated function mentions this as well:

    /// Returns a sequence of pairs (*n*, *x*), where *n* represents a
    /// consecutive integer starting at zero and *x* represents an element of
    /// the sequence.
    ///
    /// This example enumerates the characters of the string "Swift" and prints
    /// each character along with its place in the string.
    ///
    ///     for (n, c) in "Swift".enumerated() {
    ///         print("\(n): '\(c)'")
    ///     }
    ///     // Prints "0: 'S'"
    ///     // Prints "1: 'w'"
    ///     // Prints "2: 'i'"
    ///     // Prints "3: 'f'"
    ///     // Prints "4: 't'"
    ///
    /// When you enumerate a collection, the integer part of each pair is a counter
    /// for the enumeration, but is not necessarily the index of the paired value.
    /// These counters can be used as indices only in instances of zero-based,
    /// integer-indexed collections, such as `Array` and `ContiguousArray`. For
    /// other collections the counters may be out of range or of the wrong type
    /// to use as an index. To iterate over the elements of a collection with its
    /// indices, use the `zip(_:_:)` function.
    ///
    /// This example iterates over the indices and elements of a set, building a
    /// list consisting of indices of names with five or fewer letters.
    ///
    ///     let names: Set = ["Sofia", "Camilla", "Martina", "Mateo", "Nicolás"]
    ///     var shorterIndices: [Set<String>.Index] = []
    ///     for (i, name) in zip(names.indices, names) {
    ///         if name.count <= 5 {
    ///             shorterIndices.append(i)
    ///         }
    ///     }
    ///
    /// Now that the `shorterIndices` array holds the indices of the shorter
    /// names in the `names` set, you can use those indices to access elements in
    /// the set.
    ///
    ///     for i in shorterIndices {
    ///         print(names[i])
    ///     }
    ///     // Prints "Sofia"
    ///     // Prints "Mateo"
    ///
    /// - Returns: A sequence of pairs enumerating the sequence.
    ///
    /// - Complexity: O(1)

In your specific case enumerated() is fine to use since you are using a 0-based index array, however due to the details above, relying on enumerated() all the time can lead to non-obvious errors.

Take this snippet, for example:

ForEach(Array(items.enumerated()), id: \.offset) { offset, item in
  Button(item, action: { store.didTapItem(at: offset) })
}

// ...

class Store {

  var items: ArraySlice<String>

  func didTapItem(at index: Int) {
    print(items[index])
  }
}

First notice that we dodged a bullet with Button(item... since enumerated() has guaranteed that item can be accessed directly without causing an exception. However, if instead of item we used items[offset], an exception could easily be raised.

Finally, the line print(items[index]) can easily lead to an exception since the index (really the offset) can be out of bounds.

Therefore, a safer approach is to always use the zip method mentioned at the top of this post.

Another reason to prefer zip is that if you tried using the same code with a different Collection (e.g. Set) you could get the following syntax error when indexing into the type (items[index]):

Cannot convert value of type 'Int' to expected argument type 'Set.Index'

By using the zip based approach, you can still index into the collection.

You could also create an extension on collection if you plan on using it often.

You can test this all out in a Playground:

import PlaygroundSupport
import SwiftUI

// MARK: - Array

let array = ["a", "b", "c"]
Array(array.enumerated()) // [(offset 0, element "a"), (offset 1, element "b"), (offset 2, element "c")]
Array(zip(array.indices, array)) // [(.0 0, .1 "a"), (.0 1, .1 "b"), (.0 2, .1 "c")]

let arrayView = Group {
  ForEach(Array(array.enumerated()), id: \.offset) { offset, element in
    PrintView("offset: \(offset), element: \(element)")
    Text("value: \(array[offset])")
  }
//  offset: 0, element: a
//  offset: 1, element: b
//  offset: 2, element: c

  ForEach(Array(zip(array.indices, array)), id: \.0) { index, element in
    PrintView("index: \(index), element: \(element)")
    Text("value: \(array[index])")
  }
//  index: 0, element: a
//  index: 1, element: b
//  index: 2, element: c
}

// MARK: - Array Slice

let arraySlice = array[1...2] // ["b", "c"]
Array(arraySlice.enumerated()) // [(offset 0, element "b"), (offset 1, element "c")]
Array(zip(arraySlice.indices, arraySlice)) // [(.0 1, .1 "b"), (.0 2, .1 "c")]

// arraySlice[0] // ❌ EXC_BAD_INSTRUCTION
arraySlice[1] // "b"
arraySlice[2] // "c"

let arraySliceView = Group {
  ForEach(Array(arraySlice.enumerated()), id: \.offset) { offset, element in
    PrintView("offset: \(offset), element: \(element)")
    // Text("value: \(arraySlice[offset])") ❌ Fatal error: Index out of bounds
  }
//  offset: 0, element: b
//  offset: 1, element: c

  ForEach(Array(zip(arraySlice.indices, arraySlice)), id: \.0) { index, element in
    PrintView("index: \(index), element: \(element)")
    Text("value: \(arraySlice[index])")
  }
//  index: 1, element: b
//  index: 2, element: c
}

// MARK: - Set

let set: Set = ["a", "b", "c"]
Array(set.enumerated()) // [(offset 0, element "b"), (offset 1, element "c"), (offset 2, element "a")]
Array(zip(set.indices, set)) // [({…}, .1 "a"), ({…}, .1 "b"), ({…}, .1 "c")]

let setView = Group {
  ForEach(Array(set.enumerated()), id: \.offset) { offset, element in
    PrintView("offset: \(offset), element: \(element)")
    // Text("value: \(set[offset])") // ❌ Syntax error: Cannot convert value of type 'Int' to expected argument type 'Set<String>.Index'
  }
//  offset: 0, element: a
//  offset: 1, element: b
//  offset: 2, element: c

  ForEach(Array(zip(set.indices, set)), id: \.0) { index, element in
    PrintView("index: \(index), element: \(element)")
    Text("value: \(set[index])")
  }
//  index: Index(_variant: Swift.Set<Swift.String>.Index._Variant.native(Swift._HashTable.Index(bucket: Swift._HashTable.Bucket(offset: 0), age: -481854246))), element: a
//  index: Index(_variant: Swift.Set<Swift.String>.Index._Variant.native(Swift._HashTable.Index(bucket: Swift._HashTable.Bucket(offset: 2), age: -481854246))), element: b
//  index: Index(_variant: Swift.Set<Swift.String>.Index._Variant.native(Swift._HashTable.Index(bucket: Swift._HashTable.Bucket(offset: 3), age: -481854246))), element: c

}

// MARK: -

struct PrintView: View {
  init(_ string: String) {
    print(string)
    self.string = string
  }

  var string: String

  var body: some View {
    Text(string)
  }
}

let allViews = Group {
  arrayView
  arraySliceView
  setView
}

PlaygroundPage.current.setLiveView(allViews)

Updates:

Deleted the part that mentioned you can use \.1 since Peacemoon points out this could cause problems. Also I'm pretty sure if your items conform to Identifiable, there's no point in using zip in the first place, you should be able to just do ForEach(identifiableItems).

SwiftUI - Automatically add dividers between each element of a `ForEach`

Does everything need to be in a ForEach? If not, you can consider not using indices at all:

struct ForEachDividerView<Data, Content, ID>: View where Data: RandomAccessCollection, ID: Hashable, Content: View {
    var data: Data
    var id: KeyPath<Data.Element, ID>
    var content: (Data.Element) -> Content
    
    var body: some View {
        if let first = data.first {
            content(first)
            
            ForEach(data.dropFirst(), id: id) { element in
                Divider()
                    .background(.blue)
                content(element)
            }
        }
    }
}

NavigationStack Type '() - ()' cannot conform to 'View'

You have added extra { after route in and because of this Xcode added } as well. So remove this extra start { and end }. Now after fixing this in your switch case you missed handling of app case because of this you will get Switch must be exhaustive error. To fix this add app case or default case as well in your switch. After fixing both issues your code will look like this.

@main
struct MyApp: App {
    var body: some Scene {
        WindowGroup {
            NavigationStack {
                ContentView()
                    .navigationDestination(for: Route.self) { route in
                        switch route {
                        case .login:
                            Text("Login")
                        case .signup:
                            Text("Sign Up")
                        case .app:
                            Text("App")
                        }
                    }
            }
        }
    }
}

How Use Use Swiftui Foreach with a Dictionary [ Customenum: Customstrut ] - Getting "Conform to 'Randomaccesscollection'" Error