Code-along: Cook up a rich text experience in SwiftUI with AttributedString

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: String

    var body: some View {
        TextEditor(text: $text)
    }
}

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: AttributedString

    var body: some View {
        TextEditor(text: $text)
    }
}

var text = AttributedString(
  "Hello 👋🏻! Who's ready to get "
)

var cooking = AttributedString("cooking")
cooking.foregroundColor = .orange
text += cooking

text += AttributedString("?")

text.font = .largeTitle

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: AttributedString
    @State private var selection = AttributedTextSelection()

    var body: some View {
        TextEditor(text: $text, selection: $selection)
            .preference(key: NewIngredientPreferenceKey.self, value: newIngredientSuggestion)
    }

    private var newIngredientSuggestion: IngredientSuggestion {
        let name = text[selection.indices(in: text)] // build error

        return IngredientSuggestion(
            suggestedName: AttributedString())
    }
}

var text = AttributedString(
  "Hello 👋🏻! Who's ready to get cooking?"
)

guard let cookingRange = text.range(of: "cooking") else {
  fatalError("Unable to find range of cooking")
}

text[cookingRange].foregroundColor = .orange

var text = AttributedString(
  "Hello 👋🏻! Who's ready to get cooking?"
)

let uppercaseRanges = text.characters
  .indices(where: \.isUppercase)

text[uppercaseRanges].foregroundColor = .blue

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: AttributedString
    @State private var selection = AttributedTextSelection()

    var body: some View {
        TextEditor(text: $text, selection: $selection)
            .preference(key: NewIngredientPreferenceKey.self, value: newIngredientSuggestion)
    }

    private var newIngredientSuggestion: IngredientSuggestion {
        let name = text[selection]

        return IngredientSuggestion(
            suggestedName: AttributedString(name))
    }
}

import SwiftUI

struct IngredientAttribute: CodableAttributedStringKey {
    typealias Value = Ingredient.ID

    static let name = "SampleRecipeEditor.IngredientAttribute"
}

extension AttributeScopes {
    /// An attribute scope for custom attributes defined by this app.
    struct CustomAttributes: AttributeScope {
        /// An attribute for marking text as a reference to an recipe's ingredient.
        let ingredient: IngredientAttribute
    }
}

extension AttributeDynamicLookup {
    /// The subscript for pulling custom attributes into the dynamic attribute lookup.
    ///
    /// This makes them available throughout the code using the name they have in the
    /// `AttributeScopes.CustomAttributes` scope.
    subscript<T: AttributedStringKey>(
        dynamicMember keyPath: KeyPath<AttributeScopes.CustomAttributes, T>
    ) -> T {
        self[T.self]
    }
}

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: AttributedString
    @State private var selection = AttributedTextSelection()

    var body: some View {
        TextEditor(text: $text, selection: $selection)
            .preference(key: NewIngredientPreferenceKey.self, value: newIngredientSuggestion)
    }

    private var newIngredientSuggestion: IngredientSuggestion {
        let name = text[selection]

        return IngredientSuggestion(
            suggestedName: AttributedString(name),
            onApply: { ingredientId in
                let ranges = text.characters.ranges(of: name.characters)

                for range in ranges {
                    // modifying `text` without updating `selection` is invalid and resets the cursor 
                    text[range].ingredient = ingredientId
                }
            })
    }
}

text.characters[index] // "👋🏻"

text.unicodeScalars[index] // "👋"

text.runs[index] // "Hello 👋🏻! ..."

text.utf8[index] // "240"

text.utf16[index] // "55357"

var text = AttributedString(
  "Hello 👋🏻! Who's ready to get cooking?"
)

guard var cookingRange = text.range(of: "cooking") else {
  fatalError("Unable to find range of cooking")
}

let originalRange = cookingRange
text.transform(updating: &cookingRange) { text in
  text[originalRange].foregroundColor = .orange
  
  let insertionPoint = text
    .index(text.startIndex, offsetByCharacters: 6)
  
  text.characters
    .insert(contentsOf: "chef ", at: insertionPoint)
}

print(text[cookingRange])

import SwiftUI

struct RecipeEditor: View {
    @Binding var text: AttributedString
    @State private var selection = AttributedTextSelection()

    var body: some View {
        TextEditor(text: $text, selection: $selection)
            .preference(key: NewIngredientPreferenceKey.self, value: newIngredientSuggestion)
    }

    private var newIngredientSuggestion: IngredientSuggestion {
        let name = text[selection]

        return IngredientSuggestion(
            suggestedName: AttributedString(name),
            onApply: { ingredientId in
                let ranges = RangeSet(text.characters.ranges(of: name.characters))

                text.transform(updating: &selection) { text in
                    text[ranges].ingredient = ingredientId
                }
            })
    }
}

struct RecipeFormattingDefinition: AttributedTextFormattingDefinition {
    struct Scope: AttributeScope {
        let foregroundColor: AttributeScopes.SwiftUIAttributes.ForegroundColorAttribute
        let adaptiveImageGlyph: AttributeScopes.SwiftUIAttributes.AdaptiveImageGlyphAttribute
        let ingredient: IngredientAttribute
    }

    var body: some AttributedTextFormattingDefinition<Scope> {

    }
}

// pass the custom formatting definition to the TextEditor in the updated `RecipeEditor.body`:

        TextEditor(text: $text, selection: $selection)
            .preference(key: NewIngredientPreferenceKey.self, value: newIngredientSuggestion)
            .attributedTextFormattingDefinition(RecipeFormattingDefinition())

struct IngredientsAreGreen: AttributedTextValueConstraint {
    typealias Scope = RecipeFormattingDefinition.Scope
    typealias AttributeKey = AttributeScopes.SwiftUIAttributes.ForegroundColorAttribute

    func constrain(_ container: inout Attributes) {
        if container.ingredient != nil {
            container.foregroundColor = .green
        } else {
            container.foregroundColor = nil
        }
    }
}

// list the value constraint in the recipe formatting definition's body:
    var body: some AttributedTextFormattingDefinition<Scope> {
        IngredientsAreGreen()
    }

static let inheritedByAddedText = false

static let invalidationConditions:
  Set<AttributedString.AttributeInvalidationCondition>? =
  [.textChanged]

static let runBoundaries:
  AttributedString.AttributeRunBoundaries? =
  .paragraph

struct IngredientAttribute: CodableAttributedStringKey {
    typealias Value = Ingredient.ID

    static let name = "SampleRecipeEditor.IngredientAttribute"

    static let inheritedByAddedText: Bool = false

    static let invalidationConditions: Set<AttributedString.AttributeInvalidationCondition>? = [.textChanged]
}