Environment Objects

Passing an object through every view down to the one that needs it gets tedious. Put it in the environment instead, and any view below can read it:

@StateObject private var cart = Cart()

var body: some View {
    NavigationStack {
        ShopView()
    }
    .environmentObject(cart)
}

A view further down declares what it needs with @EnvironmentObject, without an initial value:

struct CartBadge: View {
    @EnvironmentObject var cart: Cart

    var body: some View {
        Text("\(cart.count) in cart")
    }
}

ShopView never mentions the cart, but CartBadge inside it still gets the same object. If no view above provides it with .environmentObject, the app stops with an error when CartBadge is shown.