0func fetchData() async -> String { return "Data loaded" } func process() async { let result = await fetchData() print(result) }
| Step | Action | Evaluation | Result |
|---|---|---|---|
| 1 | Declare async function fetchData | func fetchData() async -> String | Function ready to be called asynchronously |
| 2 | Declare async function process | func process() async | Function ready to call fetchData with await |
| 3 | Call process() | Starts async process function | process function running |
| 4 | Inside process: call await fetchData() | Wait for fetchData to complete | fetchData starts running asynchronously |
| 5 | fetchData returns "Data loaded" | Return value from fetchData | "Data loaded" |
| 6 | process receives result | Assign result = "Data loaded" | result variable set |
| 7 | process prints result | print("Data loaded") | Output: Data loaded |
| 8 | process ends | No more code | Async function completes |
| Variable | Start | After Step 5 | After Step 6 | Final |
|---|---|---|---|---|
| result | nil | nil | "Data loaded" | "Data loaded" |
Async functions use 'async' keyword in declaration. Call async functions with 'await' to pause until result. Async functions run without blocking main thread. Use 'await' only inside async functions. Return values from async functions like normal functions.
async keyword do when declaring a function in Swift?asyncasync keyword tells Swift that the function can pause its work to wait for other tasks without blocking the whole program.async does not do: it does not automatically use multiple threads, does not restrict to main thread, and does not block execution.async keyword comes after the function parentheses and before any throws keyword.func fetchData() async throws -> String {}. The other options place async incorrectly (before func, between func and name, or after throws).func greet() async -> String {
return "Hello"
}
func printGreeting() async {
let message = await greet()
print(message)
}
Task {
await printGreeting()
}greet() is async and returns "Hello". printGreeting() awaits greet() correctly and prints the message.Task block calls await printGreeting(), so the print happens inside the asynchronous context.func loadData() throws async -> String {
return "Data"
}async must come before throws in the function declaration.await keyword inside the function body. is incorrect because await is only needed when calling other async functions. Function must return Void if marked async. is wrong; async functions can return any type. Cannot combine throws with async. is false; async and throws can be combined.throws and async is incorrect. -> Option AfetchUsernames() that calls two async functions fetchFromServer() and fetchFromCache() and returns the first non-empty result. Which is the correct way to declare and use fetchUsernames()?async throws with async before throws. Calls to async throwing functions require try await.throws and try. async func fetchUsernames() -> [String] {
let server = fetchFromServer()
if !server.isEmpty {
return server
}
return fetchFromCache()
} has wrong syntax placing async before func and missing awaits. func fetchUsernames() throws async -> [String] {
let server = try fetchFromServer()
if !server.isEmpty {
return server
}
return try fetchFromCache()
} swaps throws and async and misses await. Only func fetchUsernames() async throws -> [String] {
let server = try await fetchFromServer()
if !server.isEmpty {
return server
}
return try await fetchFromCache()
} correctly declares and uses try await.Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.