Exercise: Correct mistakes with cancellation
All below code snippets contain mistakes related to cancellation. Name them and explain why they are mistakes. Write a corrected version of the code.
Function updateUser contains four mistakes. Three are related to cancellation.
suspend fun updateUser() {
val user = readUser() // blocking
val userSettings = readUserSettings(user.id) // blocking
try {
updateUserInDatabase(user, userSettings) // suspending
} catch (e: CancellationException) {
revertUnfinishedTransactions() // suspending
}
}
Function sendSignature contains three mistakes. Two are related to cancellation.
suspend fun sendSignature(file: File) {
try {
val content = file.readText()
val signature = calculateSignature(content)
sendSignature(signature) // suspending
} catch (e: Exception) {
println("Error while sending signature: ${e.message}")
e.printStackTrace()
} finally {
file.delete()
}
}
Function trySendUntilSuccess contains one mistake related to cancellation.
suspend fun trySendUntilSuccess() {
var success = false
do {
try {
send()
success = true
} catch (e: Exception) {
println("Error while sending: ${e.message}")
e.printStackTrace()
}
} while (!success)
}
Once you are done with the exercise, you can check your solution here.
