[英]Extending ObjC generic in Swift 3
Swift 3 comes with SE-0057 implemented that, among other things, means that: Swift 3随附SE-0057实现,这意味着:
By default, extensions of parameterized Objective-C classes cannot reference the type parameters in any way.
默认情况下,参数化Objective-C类的扩展不能以任何方式引用类型参数。 For example:
例如:
extension MySet { func someNewMethod(x: T) { ... } // error: cannot use `T`. }
... where MySet
is declared in ObjC as @interface MySet<T : id<NSCopying>> : NSObject
. ...其中
MySet
在ObjC中声明为@interface MySet<T : id<NSCopying>> : NSObject
。
All that is clear (and there is some sort of workaround possible even). 一切都清楚了(甚至还有某种解决方法)。 However, the following does not compile despite that I am not using any type parameters from ObjC class that I am trying to extend.
但是,尽管我没有使用我试图扩展的ObjC类的任何类型参数,但以下内容无法编译。 I am only using another unrelated Swift class as a return parameter to the extension method:
我只使用另一个不相关的Swift类作为扩展方法的返回参数:
class Foo { }
struct Bar { }
extension MySet {
func foo() -> Foo { return Foo() } // Both produce: Extension of a generic
func bar() -> Bar { return Bar() } // Objective-C class cannot access the
} // class's generic parameters at runtime
Is this a bug? 这是错误吗? Or am I missing something?
还是我错过了什么?
xCode 8.3.1, swift 3.1 xCode 8.3.1,快速3.1
MySet.h
MySet.h
#import <Foundation/Foundation.h>
@interface MySet<T : id<NSCopying>> : NSObject
@end
typedef struct ObjCStruct
{
__unsafe_unretained NSString* str;
int num;
} ObjCStruct;
MySet.m
MySet.m
#import "MySet.h"
@implementation MySet
@end
MySetExtension.swift
MySetExtension.swift
import Foundation
class Foo: NSObject {
var str = "Foo"
var num = 1
}
extension ObjCStruct {
init() {
num = 2
str = Unmanaged.passRetained("ObjCStruct")
}
}
extension MySet {
func foo() -> Foo { return Foo() }
func bar() -> ObjCStruct { return ObjCStruct() }
}
Bridging-Header
桥接头
#import "MySet.h"
NSLog(@"%@", [set foo].str);
NSLog(@"%@", [set bar].str);
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