Base example for NSProxy in Swift

NSProxyInSwift.swift

// Objective-C Header BaseProxyForSwift.h

NS_ASSUME_NONNULL_BEGIN

NS_SWIFT_NAME(BaseProxyForSwift)
@interface BaseProxyForSwift : NSProxy

+ (id)with:(id)object;

@end

NS_ASSUME_NONNULL_END

// Objective-C Implementation BaseProxyForSwift.m

#import "BaseProxyForSwift.h"

@interface BaseProxyForSwift ()
@property (nonatomic, strong) id object;
@end

@implementation BaseProxyForSwift

+ (id)with:(id)object {
    BaseProxyForSwift *res = [self alloc];
    res.object = object;
    return res;
}

@end

// Swift Implementation BaseSwiftProxy.swift

import Foundation

public class BaseSwiftProxy: BaseProxyForSwift {

}

// Usage in Swift

let a = NSObject()
let p = BaseSwiftProxy.with(a)

Don't forget about Bridging Header if you mix languages!
https://developer.apple.com/documentation/swift/importing-objective-c-into-swift