[Solved] Why does this code cause a compile error?struct ContentView: View { @State private var number = 0 func increment() { number += 1 } var body: some View { Button("Add", action: increment) } } | iOS Swift

iOS Swift - State Management in SwiftUI

Why does this code cause a compile error?

struct ContentView: View {
  @State private var number = 0
  func increment() {
    number += 1
  }
  var body: some View {
    Button("Add", action: increment)
  }
}

AFunctions cannot modify @State variables outside the body property.

Bincrement() must be marked as mutating to modify @State.

C@State variables cannot be modified inside functions.

DThe increment function is missing the @State wrapper.

Step-by-Step Solution

Solution:

Step 1: Understand mutability rules in Swift structs
Functions that modify properties in structs must be marked mutating.
Step 2: Check increment() function declaration
increment() is not marked mutating, so it cannot modify the @State variable.
Final Answer:
increment() must be marked as mutating to modify @State. -> Option B
Quick Check:
Mutating functions needed to change struct properties [OK]

Quick Trick: Mark functions mutating to change struct properties [OK]

Common Mistakes:

Assuming @State variables are class properties
Forgetting mutating keyword in struct methods
Thinking @State variables can't be changed in functions

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Why does this code cause a compile error?

Step 1: Understand mutability rules in Swift structs

Step 2: Check increment() function declaration

Final Answer:

Quick Check:

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