The weird world of observable keys 🔑👀

The get that keeps on getting.

Solution

Given a bus:

import Foundation
struct Value : Event {
  let key: String
  let val: Any?
}
protocol Store {
  func get(_ key: String)
  func set(_ key: String, _ val: Any?)
}
class LocalStore : Store {
  let db: UserDefaults
  let bus: Bus
  init(db: UserDefaults, bus: Bus){
    self.db = db
    self.bus = bus
  }
  func get(_ key: String) {
    let val = db.object(forKey: key)
    bus.pub(Value(key: key, val: val))
  }
  func set(_ key: String, _ val: Any?){
    db.set(val, forKey: key)
    bus.pub(Value(key: key, val: val))
  }
}
let bus = Bus()
bus.sub(StdoutSubscriber())
let local = LocalStore(db: UserDefaults.standard, bus: bus)
local.set("foo", "bar")
local.get("foo")

A couple features I like:

  • The bus provides a consistent interface for adding and removing subscriptions
  • There’s a straightforward get method to flush a value into the bus

Problem

If rationalizing events bubbling up from UI and disparate data sources is challenging, normalizing to a single bus interface may be helpful.

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