How do I extend the lifetime of a variable, i.e. make sure that ARC is less
aggressive?
clang has an attribute called objc_precise_lifetime — does Swift have something
similar?
I have this code:
do {
var base = UnsafePointer<Void>()
var size = Int()
let mapped = dispatch_data_create_map(backingData, &base, &size)
let buffer = UnsafeBufferPointer<A>(start: UnsafePointer<A>(base), count:
size / sizeof(A))
return someFunction(buffer)
}
I need the ‘mapped’ variable to stay in scope (i.e. not be released) until the
end of the scope, but ARC is free to release it immediately — in fact the
compiler warns me that the immutable value is never used.
But the API contract with dispatch_data_create_map(3) is that the values in
‘base’ and ‘size’ are only valid as long as ‘mapped’ is around. The above code
is passing a buffer into ‘someFunction’ that’s no longer valid.
How do I fix this?
/Daniel
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