let constant initialization in the control flow statements

Question

Created Aug ’15

Replies 3

Boosts 0

Participants 2

Hi,

According to the Swift Blog (https://developer.apple.com/swift/blog/?id=22), the rule is that a let constant must be initialized before use (like a var), and that it may only be initialized, not reassigned or mutated after initialization.

let s = "foo"

can be changed to

let s : String
s = "foo"

But in a control flow statement which surrounds the above code, the compiler gives me an error that says "Cannot assign to value: 's' is a 'let' constant." For example,

if condition {
     let s = "foo"
     print(s)
}

is OK, but

if condition {
     let s : String
     s = "foo"
     print(s)
}

is an error code.

Is my understanding is right?

Boost

Answer 1

DTS Engineer OP

Apple

Aug ’15

That is, indeed, quite strange. Notably, this only affects code at the top level of the program; the same code in a function works as expected.

func foo(condition: Bool) {
    if condition {
        let s: String 
        s = "foo"          // compiles just fine
        print(s)
    }
}

You should file a bug about this. Please post your bug number, just for the record.

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0

Answer 2

kimjs OP

Aug ’15

Thanks for your experiment in a func.

Bug number: 22322266

0

Answer 3

kimjs OP

Sep ’15

Resolved as of Xcode 7.1 beta 2 - 7B75 and closed.

0