Problem to use UnsafePointer<Int8>

Question

Alexandre Carmo OP

Created Nov ’16

Replies 1

Boosts 0

Views 3.1k

Participants 2

Hello friends.

I tried write the below line on swift 3:

let text = UnsafePointer<Int8>(sqlite3_column_text(statement, index))

But I have this error:

'init' is unavailable: use 'withMemoryRebound(to:capacity:_)' to temporarily view memory as another layout-compatible type.

I thinh that Tthis error is about UnsafePointer<Int8>

How cain I fix it?

Answered by DTS Engineer in 194660022

This is fallout from SE-0107 UnsafeRawPointer API, which puts Swift’s type aliasing rules on a firm footing. I recommend you read the UnsafeRawPointer Migration doc before going further here.

You wrote:

I think that this error is about
UnsafePointer<Int8>

Right. Swift 3 no longer lets you construct pointers of type A from pointers of type B, and in this case

sqlite3_column_text

returns a pointer to type

UInt8

.

There are a bunch of ways to fix this but the best approach depends on what you’re doing with the returned value. For example, if your final goạl is to get a Swift string, you can avoid the whole issue by using string initialisation function that takes an

UnsafePointer<UInt8>

.

let text = sqlite3_column_text(statement, index)
// `text` is of type `UnsafePointer<UInt8>`
if let text = text {
    let str = String(cString: text)
    …
} else {
    … handle the fact that text is nil …
}

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Boost

Answer 1

DTS Engineer OP

Apple

Nov ’16

Accepted Answer