swiftui button action calling wrong action

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Summary

A UI Interaction Conflict occurred where tapping a radio button in a PersonaliseCellView inadvertently triggered the action of an adjacent “Edit” button. This was caused by improper view re-rendering logic (specifically a mix of @ObservedObject and @State updates) that reset the visual state of the radio buttons within a List, effectively hijacking the touch target when the view refreshed.

Root Cause

The issue stems from the architectural conflict between SwiftUI’s View dependency management and manual state synchronization.

  1. Improper State Propagation: The PersonaliseCellView was likely initialized with a mix of binding and value semantics (passing isEditEnabled as a boolean value instead of a Binding<Bool>). When a radio button action occurred, it updated the ViewModel, triggering a full reload of the List.
  2. Unstable View Identity: As the List reloaded, ForEach generated new view instances. Because the isEditEnabled state was passed as a static value during initialization, the timing of the UI refresh caused the hit-testing logic to overlap.
  3. Tap Target Collision: During the rapid state transition, the layout engine re-drew the cells. The “Edit” button (which often had a larger tap target or was re-rendered in a displaced position) overlapped momentarily with the radio button’s touch area, causing the system to register the tap on the wrong target.

Why This Happens in Real Systems

In production SwiftUI apps, this issue is common when developers mix imperative state management with declarative UI updates without strictly adhering to MVVM principles.

  • List Performance Optimization: SwiftUI reuses views in List for performance. If you identify views by .id(\.self) or fail to provide a stable identity (like a unique ID), the system may reuse a cell that is still transitioning, leading to input conflicts.
  • Two-Way Binding Misuse: Passing values down the view hierarchy without @Binding breaks the reactive chain. When the source of truth changes (ViewModel), the child views do not update predictably, causing race conditions in the gesture recognizers.

Real-World Impact

  • UX Breakage: Users cannot select options, leading to abandonment of the feature.
  • Perceived Instability: The app feels “buggy” and unresponsive, damaging brand trust.
  • Accessibility Failure: VoiceOver and Switch Control users may find it impossible to navigate or select items if the focus moves unexpectedly to the wrong control.

Example or Code

Below is the corrected PersonaliseCellView structure. The key fix is using @Binding for the isEditEnabled state to ensure the parent List updates correctly and the child view reacts to state changes without re-initializing the entire cell.

import SwiftUI

struct PersonaliseCellView: View {
    let serviceType: String
    @Binding var isEditEnabled: Bool // FIX: Use Binding for two-way sync
    @Binding var selectedOption: PriorityOption // FIX: Binding for selection

    var setEditEnabled: (Bool) -> Void
    var changePriority: (PriorityOption) -> Void

    var body: some View {
        HStack {
            // Radio Buttons
            VStack(alignment: .leading) {
                Button(action: {
                    changePriority(.always)
                }) {
                    HStack {
                        Image(systemName: selectedOption == .always ? "largecircle.fill.circle" : "circle")
                            .foregroundColor(.blue)
                        Text("Always")
                    }
                }
                .padding(.vertical, 4)

                Button(action: {
                    changePriority(.duringPeakHoursOnly)
                }) {
                    HStack {
                        Image(systemName: selectedOption == .duringPeakHoursOnly ? "largecircle.fill.circle" : "circle")
                            .foregroundColor(.blue)
                        Text("Peak Hours")
                    }
                }
                .padding(.vertical, 4)
            }
            .contentShape(Rectangle()) // Ensures entire area is tappable
            .onTapGesture {
                // Explicit handling if needed, though Buttons handle individual taps
            }

            Spacer()

            // Edit Button
            Button(action: {
                // Toggle edit mode
                setEditEnabled(!isEditEnabled)
            }) {
                Image(systemName: isEditEnabled ? "pencil.circle.fill" : "pencil.circle")
                    .font(.title2)
                    .foregroundColor(isEditEnabled ? .green : .gray)
            }
            .buttonStyle(PlainButtonStyle()) // Prevent default button styling interference
            .contentShape(Rectangle()) // Defines safe tap area
        }
        .padding()
        .background(Color.white)
        .cornerRadius(10)
        .shadow(radius: 2)
    }
}

How Senior Engineers Fix It

Senior engineers resolve this by enforcing Single Source of Truth (SSOT) and optimizing view identities:

  1. Eliminate @ObservedObject in Subviews: Pass data via @Binding instead of observing the entire ViewModel in the cell. This prevents the cell from re-rendering the entire hierarchy when the ViewModel updates.
  2. Stable Identifiers: Ensure ForEach uses a stable, unique ID (e.g., viewModel.items[index].id) rather than the index itself or .id(\.self).
  3. Gesture Prioritization: Explicitly define contentShape and use Button components with PlainButtonStyle to ensure tap targets are strictly confined to the intended UI element.
  4. Refactoring Logic: Move the “Edit” toggle logic to the ViewModel and bind it directly, avoiding complex closure passing which often leads to capture cycles or update delays.

Why Juniors Miss It

Junior developers often struggle with this because:

  1. Misunderstanding SwiftUI State Flow: They confuse @State, @ObservedObject, and @Binding. Passing a value type (struct) or a primitive (Bool) instead of a Binding breaks the reactivity needed for the UI to stay in sync.
  2. Index-based Iteration: Using ForEach(0..<count, id: \.self) is dangerous. If the array order shifts or the view reloads, the indices might not map correctly to the underlying data, causing the UI to render stale state that triggers the wrong actions.
  3. Over-reliance on Closures: While closures (callbacks) work, they are error-prone in List views compared to bindings. Juniors often forget that the closure captures the state at the time of initialization, not at the time of execution, leading to the “wrong action” bug.