The new anomaly capture mechanism is updated with the new Swift2.0 released on WWDC 2015, and the unusual try-catch mechanism helps us locate the cause of the error faster, and here is a brief explanation of the use of the try-catch mechanism. 1. Defining enumeration Outliers First we can create our own exception enumeration value, which is to implement the ErrorType protocol, but this protocol is empty, we add just fine. 2. Throw an exception we can throw an exception in the method, it is very simple to define the method that throws the exception, just add throws to the front of the return value, the example is as follows: (This method is an instance method in a custom dog class, Name.length () Is the method that is added for the system's string class by extension)
3. Catch exception we can catch the exception by adding a catch keyword after the method that may throw the exception is called
4. Do not handle exceptions if you determine that a piece of code that might throw an exception is not likely to throw an exception, you can use try! to make the call, but if the code throws an exception, it will cause a runtime exception error, so use caution. End: It's worth noting that in a method that might throw an exception, Once an exception is thrown in one place, the method stops running immediately. The code behind the thrown exception code will not be executed with custom dog classes and code that calls the Dog class enum dogerror:errortype{
Case Nameinvaliderror
Case Ageinvaliderror
Case Namelengtherror
}
Class Dog:nsobject {
var name:string!
var age:int!
Init (name:string,age:int) {
Self.name = Name
Self.age = Age
}
Func Printdogmessage (Dog:dog) throws-string{
Print ("Dog-class: Start checking if name is invalid")
Guard Let name:string = Dog.name else{
Throw Dogerror.nameinvaliderror
}
Print ("Dog-class: Start checking if the name length is invalid")
If Name.length () < 3{
Throw Dogerror.namelengtherror
}
Print ("Dog-class: Start checking if age is invalid")
If age < 0 | | Age > 20{
Throw Dogerror.ageinvaliderror
}
Print ("Dog-class: Return message") return "dog information for" + Dog.name + "\ (dog.age)}} Test method code: Let Mydog = Dog (name:" Small white ", a GE:21) var str:string! do{
Try str = mydog.printdogmessage (Mydog)
}
catch {
Switch (Error) {
Case DogError.NameInvalidError:print ("Dog's name Invalid error")
Case DogError.NameLengthError:print ("Dog's name length error")
Case DogError.AgeInvalidError:print ("Dog's age setting is not legal")
Default:print ("Main: Catch to Dog other error")
}
} print ("Main: Last output is \ (str)")
Swift exception capture use of Try Catch
