Casting UInt16 to Int16 will occur a program crash

Question

How do i avoid a program crash, when I cast a UInt16(value over 32767) to Int16.

In Object-C is easy and safe:

uint16_t a = 32888
int16_t  b = (int16_t)a

But I don't have any idea in Swift.

Obviously you can check the range before you make the invalid cast. — Jonathon Reinhart, Nov 19 '15 at 14:41
Why use a signed 16 bit integer for a value that might be over? Just use a bigger data type... — SierraOscar, Nov 19 '15 at 14:43
I hope that the referenced thread answers your question. In your case it would be: `let a : UInt16 = 32888 ; let b = Int16(bitPattern: a)`. — Martin R, Nov 19 '15 at 14:48
@MartinR This is the right answer, you should make it a formal answer that can be accepted. — Rick, Jan 10 '22 at 03:05

score -1 · Accepted Answer · answered Nov 19 '15 at 14:44

-1

You can use the following function:

func toInt(unsigned: UInt) -> Int {

    let signed = (unsigned <= UInt(Int.max)) ?
        Int(unsigned) :
        Int(unsigned - UInt(Int.max) - 1) + Int.min

    return signed
}

answered Nov 19 '15 at 14:44

Mika

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thanks! It works very well. – CocoaUser Nov 19 '15 at 14:58
`numericCast(...)` is what you're looking for. It's a set of generic functions that converts from and to different number types. It picks the correct implementation based on the types of its argument and the return type. – stigi May 31 '16 at 01:03

Casting UInt16 to Int16 will occur a program crash

1 Answers1