Apple App-Development-with-Swift-Certified-User 問題集

質問 1：
Review the code.
var capitalCities = [ " USA " : " Washington D.C. " , " Spain " : " Madrid " , " Peru " : " Lima " ] Which two statements add the capital city of " Italy " to the dictionary? (Choose 2.)
A. capitalCities[ " Rome " ] = " Italy "
B. capitalCities[ " Italy " ] = " Rome "
C. capitalCities = capitalCities + [ " Italy " : " Rome " ]
D. capitalCities.updateValue( " Rome " , forKey: " Italy " )
E. capitalCities.append([ " Italy " : " Rome " ])
正解：B,D

質問 2：
Select the area in Xcode that allows you to display the Preview Canvas.

正解：

Explanation:
This question belongs to Xcode Developer Tools , specifically the objective domain on identifying and using the features of the Xcode interface . In the screenshot, the correct area is the upper-right corner of the editor toolbar , where Xcode provides the control for editor display options. Apple's documentation explains that to show previews, you can use the editor controls and specifically notes that you can click the Adjust Editor Options button and choose Preview , which displays the preview canvas to the right of the editor.
So, in hotspot terms, the correct selection is the editor options control near the top-right of the code editor
, not the Run button, not the Inspector, and not the Project navigator. This aligns with Apple's preview workflow for SwiftUI in Xcode, where the canvas is shown from the editor display controls. Apple also describes the preview canvas as part of Xcode's interface for quickly visualizing UI changes while editing code.



質問 3：
Which property wrapper allows you to read data from the system or device settings?
A. @StateObject
B. @Environment
C. @Binding
D. @State
正解：B
解説: (Topexam メンバーにのみ表示されます)

質問 4：
In SwiftUI, how can you extract a subview from a main view to make the code more modular?
A. Use @State to manage subview content and use a binding to create a two-way connection.
B. Declare the subview as a variable inside the main view and call it directly.
C. Create a new SwiftUI view struct and call it in the main view.
D. Add the subview's code directly into the main view's body.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 5：
Match the Swift Properly Wrapper names to the correct descriptions.

正解：

Explanation:
* @AppStorage # This property wrapper reads and writes values from UserDefaults.
* @Environment # This property wrapper allows you to access data from the system, such as knowing the size class of the device, or dismissing a view.
* @Binding # When a variable is declared with this property wrapper, changes to its value will be returned to the calling view.
* @State # When a variable is declared with this property wrapper, it is used to store small amounts of data local to the view whose value may affect the appearance of the view.
This question belongs to View Building with SwiftUI , specifically the objective about using @State,
@Binding, @Environment, and related wrappers to share and manage data between views. @AppStorage is the wrapper that connects a SwiftUI value to UserDefaults, so it is the correct match for reading and writing persisted user defaults data. Apple documents AppStorage as a property wrapper type that reflects a value from UserDefaults and updates the view when that value changes.
@Environment is used to read values supplied by the system or ancestor views, including interface context like size classes and actions such as dismissing a presented view. Apple's environment documentation explains that SwiftUI automatically sets and updates many environment values for layout and behavior, and App Dev Training materials show environment values being used to dismiss a view.
@Binding represents a two-way connection to a value owned elsewhere, typically in a parent view, so changes made through the binding are reflected back in the source of truth. Apple's SwiftUI data-flow guidance describes bindings as the mechanism used when a child view needs shared control of state with another view.
@State is the correct wrapper for small, local, mutable view state. Apple describes State as the source of truth for data local to a view and recommends it for interface state that affects rendering.