In Swift's switch structure, the usage of the Fallthrough note summarizes

In Swift's switch, the case is followed by the use of Fallthrough, which is the same as the usage without break after OC case!

The use of Fallthrough should be noted:

1. When Fallthrough is added, the following case or default statement will be run immediately, regardless of whether the condition is satisfied or not

var age = 10
switch age {
     case 0 ... 10:
         print ("little friend")
         fallthrough
     case 11 ... 20:
         print ("big friend")
     case let x:
         print ("\ (x) year-old friend")
}

// Output result:
Children
Big friend 

2. After adding the Fallthrough statement, the "following next" case condition cannot define constants and variables

var age = 10
switch age {
     case 0 ... 10:
         print ("little friend")
         fallthrough // Report error here
     case let x:
         print ("\ (x) year-old friend")
}

// The program reports an error:
‘Fallthrough’ cannot transfer control to a case label that declares variables 

The reason, I understand is: by the 1th we know that the first case after the execution (the output "children") will directly execute the next case, and the next scenario defines a temporary variable x, so that the direct from the previous cases come in without this variable x, If x is used in the case statement, it will obviously go wrong. Swift is a language that requires security, which is not allowed to happen, so it is not allowed to define constants/variables in a case condition after fallthrough--except for the next one followed, the other case can define constants/variables

3. After executing the Fallthrough, jump directly to the next conditional statement, the statement after the condition execution statement does not execute

var age = 10
switch age {
     case 0 ... 10:
         print ("little friend")
         fallthrough
         print ("I jumped") // This sentence was not executed
     case 11 ... 20:
         print ("big friend")
     case let x:
         print ("\ (x) year-old friend")
}

// Output result:
Children
Big friend 

If you have any questions, please leave a message to tell me!

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In Swift's switch structure, the usage of the Fallthrough note summarizes