The withUnsafeMutableBytes method has two generic parameters, ResultType
and ContentType:
|mutating func withUnsafeMutableBytes<ResultType, ContentType>(_ body:
(UnsafeMutablePointer
<dash-apple-api://load?request_key=hsAKsXE560&language=swift><ContentType>)
throws -> ResultType) rethrows -> ResultType|
In your examples, the type checker can't infer the type of ResultType.
You'll have to state it explicitly by specifying the type of the
closure's argument. For example:
msg.withUnsafeMutableBytes {
(inPointer*: UnsafeMutablePointer<UInt8>*) -> Void in
// ...
}
On 25.04.2017 10:45, Rick Mann via swift-users wrote:
The following playground reproduces an issue I'm having, in that the code won't
compile depending on the content of the closure. In fact, an empty closure is
fine, but when I try to call certain things, it's not.
I figure it has something to do with the type inference for inPointer, but I
can't figure out what it needs to work.
---------------------------
import Foundation
// OKAY:
var msg = Data(capacity: 123456)
msg.withUnsafeMutableBytes
{ (inPointer) -> Void in
foo(inPointer)
}
//error: cannot convert value of type '(_) -> Void' to expected argument type
'(UnsafeMutablePointer<_>) -> _'
//{ (inPointer) -> Void in
//^~~~~~~~~~~~~~~~~~~~~~~~
msg.withUnsafeMutableBytes
{ (inPointer) -> Void in
}
//error: cannot convert value of type '(_) -> Void' to expected argument type
'(UnsafeMutablePointer<_>) -> _'
//{ (inPointer) -> Void in
//^~~~~~~~~~~~~~~~~~~~~~~~
msg.withUnsafeMutableBytes
{ (inPointer) -> Void in
var s: Int
lgs_error(inPointer, 123456, &s)
}
func
foo(_ data: UnsafeMutableRawPointer!)
{
}
func
lgs_error(_ message: UnsafeMutablePointer<Int8>!,
_ message_capacity: Int,
_ message_size: UnsafeMutablePointer<Int>!) -> Int
{
}
---------------------------
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