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How to fix “Cannot assign to property: 'self' is immutable”

Paul Hudson    @twostraws   

Updated for Xcode 12.0

SwiftUI’s views should be structs, which means they are immutable by default. If this were our own code we could mark methods using mutating to tell Swift they will change values, but we can’t do that in SwiftUI because it uses a computed property.

If you want to change a property’s value while your program runs, you should mark it using @State, like this:

@State private var runCount = 0

For more complex properties, such as reference types or values that are shared across multiple views, you should use @ObservedObject or @EnvironmentObject instead.

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