CODEWITHSUNDEEP
swiftswift2
Icaro
Icaro

Reputation: 14845

New control transfer statements (labels) for Swift 2.0

What would be the best practices for the new control transfer statements (labels) in Swift 2?

Since I hear about it I can't stop compare it with the goto command from the good and old Basic language, what never was well accepted from experient programmers at the time.

Some uses of the control flow transfer looks ok, like in example below:

outer: for i in 1...100{
  for j in 1...100{
    print("\(i), \(j)")
    if j == 10 {
      break outer
    }
  }
}

But what are the limitations for the control flow transfer use?

When start to be bad practice to use it?

If its use was such a bad practice why it is back?

Upvotes: 1

Views: 2106

Answers (2)

Shailesh Chandavar
Shailesh Chandavar

Reputation: 1614

You can prefix a loop statement, an if statement, or a switch statement with a statement label followed by a colon (:) ,break and continue statements are used to change control flow in a loop statement or a switch statement.

break statement breaks the current loop execution where as continue just breaks current iteration.

consider:

     firstLoop :for j in 0...1{
      secondLoop: for i in 0...10{
        if (i % 2) == 0{
          if (i == 4){
             break firstLoop
          }
          print(i)
         }
       }
      }

Output will be : 0,2

If we replace break firstloop by break secondLoop o/p Will be: 0,2,0,2

If we replace break firstloop by continue o/p Will be: 0,2,6,8,10,0,2,6,8,10

If we replace break firstloop by continue firstloop continue o/p Will be again : 0,2,0,2

If continue is followed by a statement label then it will stop the current iteration of that statement label not the loop pointed by statement label.

goto VS statement label

. goto is a kind of unconditional branching ,where you can branch anywhere in the program,The goto statement is discouraged , because it alters the sequential flow of logic .

Why statement Label is used and what is it's Limitation?

. where as continue and break can make use of statement label if and only if it is written inside the loop which has same statement label which it is using so the code will be more safer. It makes programers life easy , off course you can't directly branch out to any part of program using continue,break and statement Label it can be considered as a limitation.

Upvotes: 3

Duncan C
Duncan C

Reputation: 131426

I think you are asking about using labels for break and continue statements. That is a much more limited, safer use than the horrible goto statements from basic. It simply lets you tell the compiler the scope you need to break out of/continue when you have nested looping constructs.

As far as I know break and continue is the only use of labels in Swift, and for that it seems useful and appropriate.

Upvotes: 2

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