在Swift中，Objective-C类的属性是否可以满足Swift @obj协议计算属性要求？

Question

For instance, I want to extract a Swift protocol from my existing Objective-C class MyFoo . Let's call this protocol FooProtocol .

The situation looks like this:

// In Objective-C
@interface MyFoo
@property(nonatomic, copy) NSString *foo;
@end
@implementation MyFoo
// ... -(instancetype)initWithString: is implemented here
@end

// In Swift
@objc protocol FooProtocol {
    var foo: String { get set }
}

extension MyFoo: FooProtocol {
    // do nothing here!
}

Then I should be allowed to do this:

let theFoo: FooProtocol = MyFoo(string: "Awesome")
NSLog("\(theFoo.foo)") // Prints awesome.

But I get told "MyFoo does not conform to protocol FooProtocol". Okay. Fair enough, I guess the protocol extension needs a little nudge:

extension MyFoo: FooProtocol {
    var foo: String! { get { return foo } set { NSLog("noop") }}
}

but I'm getting errors from the compiler that look like

Getter for 'foo' with Objective-C selector 'foo' conflicts with previous declaration with the same Objective-C selector

What am I doing wrong?

Answer 1

The interfaces have different signatures and therefore the compiler doesn't really know what to do.

Try this:

// In Objective-C
@interface MyFoo
@property(nonatomic, copy) NSString *foo;
@end
@implementation MyFoo
// ... -(instancetype)initWithString: is implemented here
@end

// In Swift
@objc protocol FooProtocol {
    var foo: NSString { get set }
}

extension MyFoo: FooProtocol {
    // do nothing here!
}