5.10 Cocoa Foundation
The ffi/unsafe/nsalloc and ffi/unsafe/nsstring libraries provide basic facilities for working with Cocoa and/or Mac OS X Foundation libraries (usually along with ffi/objc).
5.10.1 Strings
| (require ffi/unsafe/nsstring) |
value
_NSString : ctype?
A type that converts between Racket strings and
NSString (a.k.a. CFString)
values. That is, use _NSString as a type for a foreign-function
NSString argument or result.
The _NSString conversion keeps a weak mapping from Racket strings to converted strings, so that converting the same string (in the equal? sense) multiple times may avoid allocating multiple NSString objects.
5.10.2 Allocation Pools
Calling any Foundation API that
allocates requires an NSAutoreleasePool installed. The
ffi/unsafe/nsalloc library provides a function and
shorthand syntactic form for setting up such a context. (The
_NSString type creates an autorelease pool implicitly while
converting from/to a Racket string, however.)
procedure
(call-with-autorelease thunk) → any
thunk : (-> any)
Calls thunk in atomic mode and with a fresh
NSAutoreleasePool that is released after thunk
returns.
syntax
(with-autorelease expr)