Swift for in loop with parentheses

Question

I normally use the for in loop in swift without parentheses, but today I put them on just for kicks thinking they were just optional and it did not worked as expected.

This code works:

if let tasks = getAllTasksWithManagedObjectContext(appDelegate.managedObjectContext){
    for task in tasks{
        appDelegate.managedObjectContext.deleteObject(task)
    }
}

This one does not:

if let tasks = getAllTasksWithManagedObjectContext(appDelegate.managedObjectContext){
    for (task in tasks){
        appDelegate.managedObjectContext.deleteObject(task)
    }
}

I get this errors: Whats going on here?

Answer 1

You are simply not allowed to use parentheses here.

Take a look at the Language Reference -> Statements and compare the C-style for-loop against the swift for-in

for-statement → for­ for-init­;­expression­;­expression­ ­code-block
for-statement → for­ (for-init­;­expression­;­expression­) ­code-block

vs.

for-in-statement → for ­case(opt) ­pattern ­in ­expression ­where-clause­(opt­) code-block

The first one can be used with or without parentheses - your choice as the developer.

However the later one, the one you are actually asking about does not have a version with ( and ), only the one version without them. That means that it is not allowed to use them parentheses around the "argument" of the loop.

Screenshots from the docs linked above for better readability:

vs.