Expose a constant variable from Objective-C to Swift - objective-c

Question

I have to do a bitwise operation that is for some reason only possible in swift so I am looking to initialize some constants with Objective-C to be used within my application.
I am not that great with objective-c yet so the only way I knew how to do this was to create a class and give it a method that returns the value but I figure that there is a more efficient value.
There must be a more succinct way to achieve this. Currently I am doing the following:
Header:
#import <Foundation/Foundation.h>
#include <simd/simd.h>
#import <MetalKit/MetalKit.h>
#import <Metal/Metal.h>
#interface Bridge:NSObject
#property NSString *url;
- (MTLTextureUsage)readAndWrite;
#end
Implementation:
#import "MPS-Bridging-Header.h"
#implementation Bridge
- (MTLTextureUsage)readAndWrite {
return MTLTextureUsageShaderRead | MTLTextureUsageRenderTarget | MTLTextureUsageShaderWrite;
}
#end
Swift Usage:
let bridge = Bridge()
Texture.usage = bridge.readAndWrite()
It would be great if this could be simplified to like
MTLTexReadAndWrite as if it were a constant or perhaps have it so that I can do Bridge().readAndWrite() so it is all on one line?

Answer 1

If you wanted to expose this to Swift, I'd define a class property:
// Bridge.h
#import Foundation;
#import Metal;
#interface Bridge : NSObject
#property (class, nonatomic, readonly) MTLTextureUsage readAndWrite;
#end
And
// Bridge.m
#import "Bridge.h"
#implementation Bridge
+ (MTLTextureUsage)readAndWrite {
return MTLTextureUsageShaderRead | MTLTextureUsageRenderTarget | MTLTextureUsageShaderWrite;
}
#end
And you could then use it like so:
let readAndWrite = Bridge.readAndWrite
But I wonder why you don't just define this constant in Swift:
let readAndWrite: MTLTextureUsage = [.shaderRead, .renderTarget, .shaderWrite]
If you need the same constant in both Objective-C and Swift, use the above bridging pattern, but if you only need it in Swift, then I'd just define it there and eliminate Bridge altogether.