The code snippet: ```swift if case .active = planChange { ``` is a pattern-matching...

The code snippet:

if case .active = planChange {

is a pattern-matching condition written in Swift, and here's what it does:

1. Pattern Matching: It checks whether the variable planChange matches the active case of an enumeration type. It assumes planChange is an instance of an enum and .active is one of its cases.

2. Scope of Check:

   • If planChange is indeed .active, the condition evaluates to true, and the code block following the if will execute.
   • If planChange is not .active (e.g., it's some other case of the enum), the condition evaluates to false, and the block won't execute.

3. Usage Context: The case keyword in an if statement is often used when checking specific cases of enums, especially when the case you're matching doesn't have associated values or you're not interested in those associated values. For cases with associated values, you can optionally bind those values in the pattern match.

   Example:

   enum PlanState {
       case active
       case inactive
       case pending
   }
   
   let planChange: PlanState = .active
   
   if case .active = planChange {
       print("The plan is active.")
   }
   

   Output:

   The plan is active.
   

Summary:

This code checks if the value of planChange is .active. If so, the condition succeeds and its associated block executes. It's a concise way to match enum cases in Swift.