[英]Matching a Swift protocol from an Objective-C Protocol instance
I'm looking for a way to match dynamically an Objective-C Protocol
instance with a corresponding Swift protocol. 我正在寻找一种方法来动态匹配Objective-C
Protocol
实例与相应的Swift协议。
I have a protocol defined in swift that is compatible with Objective-C: 我在swift中定义了一个与Objective-C兼容的协议:
@objc(YHMyProtocol) protocol MyProtocol { }
I try to perform the match, in a function: 我试着在一个函数中执行匹配:
public func existMatch(_ meta: Protocol) -> Bool {
// Not working
if meta is MyProtocol {
return true
}
// Not working also
if meta is MyProtocol.Protocol {
return true
}
return false
}
This function is intended to be called from an Objective-C file: 此函数旨在从Objective-C文件中调用:
if([Matcher existMatch:@protocol(YHMyProtocol)]) {
/* Do Something */
}
The existMatch
function always returns false. existMatch
函数始终返回false。
I can not figure out how to solve this. 我无法弄清楚如何解决这个问题。 Did I miss something in the implementation?
我是否遗漏了实施中的内容?
Protocol
is an opaque object type. Protocol
是一种不透明的对象类型。 It's defined in the generated header as: 它在生成的头文件中定义为:
// All methods of class Protocol are unavailable.
// Use the functions in objc/runtime.h instead.
OBJC_AVAILABLE(10.0, 2.0, 9.0, 1.0, 2.0)
@interface Protocol : NSObject
@end
It doesn't conform to MyProtocol
, so is MyProtocol
cannot work. 它不符合
MyProtocol
,因此is MyProtocol
无法正常工作。 And, although Swift can implicitly bridge @objc
protocol metatypes to Protocol
, it appears that it cannot do the reverse; 而且,虽然斯威夫特可以隐桥
@objc
协议元类型,以Protocol
,看来,它不能做反向; which is why is MyProtocol.Protocol
doesn't work (but even if it did, it wouldn't work for derived protocols; as P.Protocol
types can currently only hold the value P.self
). 这就是为什么
is MyProtocol.Protocol
不起作用(但即使它确实如此,它也不适用于派生协议;因为P.Protocol
类型目前只能保持值P.self
)。
If you want to check that meta
is a protocol type that is equivalent to, or derives from, MyProtocol
, you can use the Obj-C runtime function protocol_conformsToProtocol
: 如果要检查
meta
是与MyProtocol
等效或派生的协议类型,可以使用Obj-C运行时函数protocol_conformsToProtocol
:
@objc(YHMyProtocol) protocol MyProtocol { }
@objc protocol DerviedMyProtocol : MyProtocol {}
@objc class Matcher : NSObject {
@objc public class func existMatch(_ meta: Protocol) -> Bool {
return protocol_conformsToProtocol(meta, MyProtocol.self)
}
}
// the following Swift protocol types get implicitly bridged to Protocol instances
// when calling from Obj-C, @protocol gives you an equivalent Protocol instance.
print(Matcher.existMatch(MyProtocol.self)) // true
print(Matcher.existMatch(DerviedMyProtocol.self)) // true
If you just want to check that meta
is equivalent to MyProtocol
, you can use protocol_isEqual
: 如果您只想检查
meta
是否等同于MyProtocol
,则可以使用protocol_isEqual
:
@objc class Matcher : NSObject {
@objc public class func existMatch(_ meta: Protocol) -> Bool {
return protocol_isEqual(meta, MyProtocol.self)
}
}
print(Matcher.existMatch(MyProtocol.self)) // true
print(Matcher.existMatch(DerviedMyProtocol.self)) // false
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