json.rs

/*
Representing JSON in Rust objects
All objects will always have an ID and Type, but all other fields vary

[
  	{
	  id: 12345,
	  type: "photo",
	  photo_url: "asdasda.com"
	},
	{
	  id: 12346,
	  type: "text",
	  body: "some text"
	}
]
*/

// The first way one can solve this problem is accessor methods on a trait
// this feels very hacky :(

trait BasePost {
  fn id() -> i32;
  fn type() -> SomeEnum;
}

impl BasePost for PhotoPost {
 // impl those trait methods 
}

impl PhotoPost {
 // impl photo specific methods
  fn photo_url() -> String {
    // ...
  }
}

// This has the advantage that if a type of post was known at compile time, we can do something easily like
// `myPhotoPost.photo_url()`.  However, accessor methods feel very java-y and seem like a bad choice.

// Another option could be an enum with data.  Something like this:

struct Post {
   type: PostType,
   id: i32
}

// we only have one struct type but have an enum that holds specialized data.
enum PostType {
  Photo(PhotoData),
  Text(TextData)
}

// The upside of this is that there aren't any ugly accessor methods.  The downside is that we would need to match results any time
// that we wanted to access special data.  For example - 

myPost.id; // works great!  We will always have an `id` on our post type.

// but to get something like `photo_url` we'd first need to make sure the object had the Photo enum
let url = match myPost.type {
 PostType::Photo => myPost.photo_url
}


/// Which one of these methods is preferred?  Is there a better way to do this?  Basically, I'm working around the fact that rust does 
/// (not yet at least) allow fields in traits.  In a perfect world, I could do the following:
trait Post {
  id: i32,
  type: PostType
}

struct PhotoPost : Post {
  photo_url: String 
}

myPhotoObject.id;
myPhotoObject.photo_url;