我正在尝试使用(现在私有的)CTTelephonyCenterAddObserver C函数和CFNotificationCallback回调块来侦听CoreTelephony通知.
我的桥接头(外部私有C函数)：
#include <CoreFoundation/CoreFoundation.h>
#if __cplusplus
extern "C" {
#endif
#pragma mark - API
/* This API is a mimic of CFNotificationCenter. */
CFNotificationCenterRef CTTelephonyCenterGetDefault();
void CTTelephonyCenterAddObserver(CFNotificationCenterRef center,const void *observer,CFNotificationCallback callBack,CFStringRef name,const void *object,CFNotificationSuspensionBehavior suspensionBehavior);
void CTTelephonyCenterRemoveObserver(CFNotificationCenterRef center,const void *object);
void CTTelephonyCenterRemoveEveryObserver(CFNotificationCenterRef center,const void *observer);
void CTIndicatorsGetSignalStrength(long int *raw,long int *graded,long int *bars);
#pragma mark - Definitions
/* For use with the CoreTelephony notification system. */
extern CFStringRef kCTIndicatoRSSignalStrengthNotification;
#if __cplusplus
}
#endif
我的Swift代码：
let callback: CFNotificationCallback = { (center: CFNotificationCenter?,observer: UnsafeRawPointer?,name: CFString?,object: UnsafeRawPointer?,info: CFDictionary?) -> Void in
// ...
}
CTTelephonyCenterAddObserver(CTTelephonyCenterGetDefault().takeUnretainedValue(),nil,callback,kCTIndicatoRSSignalStrengthNotification.takeUnretainedValue(),.coalesce)
但是,我无法获得我的完成变量的签名以匹配CFNotificationCallback typealias的要求.
06002
如何让@convention(c)闭包在Swift中很好地玩？
让编译器推断闭包的签名工作正常：
let callback: CFNotificationCallback = { center,observer,name,object,info in
//works fine
}
试图在闭包声明中指定@convention(c)会出错：
let callback: CFNotificationCallback = { @convention(c) (center: CFNotificationCenter?,info: CFDictionary?) -> Void in
//Attribute can only be applied to types,not declarations.
}
似乎正在发生的事情是,当您手动声明闭包的类型时,它会强制编译器使用该确切类型.但这在技术上是一个闭包声明而不是类型声明,因此不允许@convention属性.当允许编译器推断闭包的类型时(根据它所存储的变量的类型),它也可以推断出属性.
