MVVM pattern in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a ViewModel class in Swift.

iOS Swift

class [1] {
  // ViewModel properties and methods
}

Drag options to blanks, or click blank then click option'

AViewModel

BModel

CViewController

DView

Attempts:

3 left

💡 Hint

Common Mistakes

Naming the ViewModel as ViewController or Model.

The ViewModel class holds the data and logic for the view. Naming it ViewModel follows the MVVM pattern.

2fill in blank

medium

Complete the code to bind a ViewModel property to update the view using Combine.

iOS Swift

@Published var name: String = ""

var cancellables = Set<AnyCancellable>()

viewModel.$name
  .[1] { newName in
    self.label.text = newName
  }
  .store(in: &cancellables)

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Asink

Bassign

Cmap

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'assign' which requires a writable key path, or 'map' which transforms values.

The sink operator subscribes to changes and executes the closure to update the UI.

3fill in blank

hard

Fix the error in the ViewModel initializer to properly initialize the model property.

iOS Swift

class ViewModel {
  private var model: Model

  init() {
    self.model = [1]
  }
}

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Anil

BModel

Cself.model

DModel()

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning the type name or nil instead of an instance.

You must create a new instance of Model by calling Model() to initialize the property.

4fill in blank

hard

Fill both blanks to create a computed property in ViewModel that returns the model's title in uppercase.

iOS Swift

var uppercaseTitle: String {
  return model.title[1][2]()
}

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A.

Buppercased

CuppercaseString

D()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'uppercaseString' which is Objective-C style, or missing the dot operator.

Use the dot operator to call the uppercased() method on the string.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that filters model data with values greater than 10.

iOS Swift

let filteredData = model.data.filter { $0.value [1] 10 }.reduce(into: [:]) { $0[[2]] = [3] }

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A>

B$1.key

C$1.value

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>', or mixing up key and value in reduce.

The filter uses > to keep values greater than 10. The reduce builds a dictionary using the key and value from each element.