Swift Language Error Handling Catch and Switch Pattern for Explicit Error Handling
Example
class Plane {
enum Emergency: ErrorType {
case NoFuel
case EngineFailure(reason: String)
case DamagedWing
}
var fuelInKilograms: Int
//... init and other methods not shown
func fly() throws {
// ...
if fuelInKilograms <= 0 {
// uh oh...
throw Emergency.NoFuel
}
}
}
In the client class:
let airforceOne = Plane()
do {
try airforceOne.fly()
} catch let emergency as Plane.Emergency {
switch emergency {
case .NoFuel:
// call nearest airport for emergency landing
case .EngineFailure(let reason):
print(reason) // let the mechanic know the reason
case .DamagedWing:
// Assess the damage and determine if the president can make it
}
}
