我正在關(guān)注從golang調(diào)用objective-c代碼的教程。教程在這個(gè)鏈接代碼如下（教程上也一樣）main.gopackage mainimport ( "fmt" "net/url" "strconv" "unsafe")//#cgo CFLAGS: -x objective-c//#cgo LDFLAGS: -framework Foundation//#include "foundation.h"import "C"// NSString -> C stringfunc cstring(s *C.NSString) *C.char { return C.nsstring2cstring(s) }// NSString -> Go stringfunc gostring(s *C.NSString) string { return C.GoString(cstring(s)) }// NSNumber -> Go intfunc goint(i *C.NSNumber) int { return int(C.nsnumber2int(i)) }// NSArray lengthfunc nsarraylen(arr *C.NSArray) uint { return uint(C.nsarraylen(arr)) }// NSArray itemfunc nsarrayitem(arr *C.NSArray, i uint) unsafe.Pointer { return C.nsarrayitem(arr, C.ulong(i))}// NSURL -> Go url.URLfunc gourl(nsurlptr *C.NSURL) *url.URL { nsurl := *C.nsurldata(nsurlptr) userInfo := url.UserPassword( gostring(nsurl.user), gostring(nsurl.password), ) host := gostring(nsurl.host) if nsurl.port != nil { port := goint(nsurl.port) host = host + ":" + strconv.FormatInt(int64(port), 10) } return &url.URL{ Scheme: gostring(nsurl.scheme), User: userInfo, // username and password information Host: host, // host or host:port Path: gostring(nsurl.path), RawQuery: gostring(nsurl.query), // encoded query values, without '?' Fragment: gostring(nsurl.fragment), // fragment for references, without '#' }}// NSArray<NSURL> -> Go []url.URLfunc gourls(arr *C.NSArray) []url.URL { var result []url.URL length := nsarraylen(arr) for i := uint(0); i < length; i++ { nsurl := (*C.NSURL)(nsarrayitem(arr, i)) u := gourl(nsurl) result = append(result, *u) } return result}func UserApplicationSupportDirectories() []url.URL { return gourls(C.UserApplicationSupportDirectories())}func main() { fmt.Printf("%#+v\n", UserApplicationSupportDirectories())}
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慕碼人2483693
TA貢獻(xiàn)1860條經(jīng)驗(yàn) 獲得超9個(gè)贊
C.NSStringCGO 生成的與NSStringObjective-C 不兼容。為避免來(lái)自編譯器的警告消息，例如 in const char* nsstring2cstring()，NSString應(yīng)void*在您的 Objective-C 代碼函數(shù)中作為 in 參數(shù)傳遞(foundation.m foundation.h)，并將您的void*toNSString和返回為C const char*：
const char* nsstring2cstring(void* s) {
if (s == NULL) { return NULL; }
NSString *cs = *((__unsafe_unretained NSString **)(s));
const char *cstr = [cs UTF8String];
return cstr;
}
在main.goGo 代碼函數(shù)中，它需要C.NSString作為unsafe.Pointerto傳遞nsstring2cstring(void*)
// NSString -> C string
func cstring(s *C.NSString) *C.char { return C.nsstring2cstring(unsafe.Pointer(s)) }
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