This is not a question, but rather the solution and an explanation of a missing step in the iOS App Dev Tutorial. I hope this helps somebody else encountering the same issue and ultimately leads to a change to the tutorial. There is a step missing from the iOS App Dev Tutorial under the Passing Data with Bindings part in Section 3 before Step 6. Namely, the update function has not been defined on the DailyScrum struct. This results in the following errors in DetailView.swift when calling scrum.update(from: data): Argument passed to call that takes no arguments Cannot use mutating member on immutable value: 'self' is immutable Referencing instance method 'update()' requires wrapper 'Binding<DailyScrum>' The files for the complete project at the end of the Passing Data with Bindings part provides the solution: you must add an update function to the DailyScrum model. Add the following inside the extension DailyScrum code block:    mutating func update(from data: Data) {      title = data.title      attendees = data.attendees      lengthInMinutes = Int(data.lengthInMinutes)      theme = data.theme   } When complete, your DailyScrum.swift file should appear as follows at this stage in the tutorial. import Foundation struct DailyScrum: Identifiable {   let id: UUID   var title: String   var attendees: [Attendee]   var lengthInMinutes: Int   var theme: Theme       init(id: UUID = UUID(), title: String, attendees: [String], lengthInMinutes: Int, theme: Theme) {     self.id = id     self.title = title     self.attendees = attendees.map { Attendee(name: $0) }     self.lengthInMinutes = lengthInMinutes     self.theme = theme   } } extension DailyScrum {   struct Attendee: Identifiable {     let id: UUID     var name: String           init (id: UUID = UUID(), name: String) {       self.id = id       self.name = name     }   }       struct Data {     var title: String = ""     var attendees: [Attendee] = []     var lengthInMinutes: Double = 5     var theme: Theme = .seafoam   }       var data: Data {     Data(title: title, attendees: attendees, lengthInMinutes: Double(lengthInMinutes), theme: theme)   }       mutating func update(from data: Data) {     title = data.title     attendees = data.attendees     lengthInMinutes = Int(data.lengthInMinutes)     theme = data.theme   } } extension DailyScrum {   static let sampleData: [DailyScrum] =   [     DailyScrum(title: "Design", attendees: ["Cathy", "Daisy", "Simon", "Jonathan"], lengthInMinutes: 10, theme: .yellow),     DailyScrum(title: "App Dev", attendees: ["Katie", "Gray", "Euna", "Luis", "Darla"], lengthInMinutes: 5, theme: .orange),     DailyScrum(title: "Web Dev", attendees: ["Chella", "Chris", "Christina", "Eden", "Karla", "Lindsey", "Aga", "Chad", "Jenn", "Sarah"], lengthInMinutes: 5, theme: .poppy)   ] }