PropertyObservable

When using pure Swift class, there is no KVO mechanism on stored property. It is also possible to use didSet closure but it is not flexible in the end.

In this project, there is a class call Property. Property is a generic class and also a proxy for your stored property. We can use Property to wrap any value type, like Int, String, Float etc. Then, we use observe(_:) function to monitor value change event.

The observe(_:) function also returns a receipt after registering the observation. We can use this receipt to invalidate the observation just by invoking invalidate() function on the receipt.

How To Use

Observe Value Change

struct Bob {
    let age: Property<Int> = Property<Int>(0)
}

let bob = BOB()
bob.age <<< 30  // custom infix operator for setting value
let observerReceipt = bob.age.observe { (new, old) in
    print("Bob's is getting old on his new age \(new). He was \(old) last year")
}
bob.age <<< 31

Invalidate Observation

observerReceipt.invalidate()

Custom Operator

When setting or getting value from Property, we can use set(_:) or get() to do so. However, we can also use custom operator to set value and get value.

// Setter
bob.age.set(30)
// is equivalent to
bob.age <<< 30

// Getter
_ = bob.age.get()
// is equivalent to 
_ = <<<bob.age 
// Be aware that no space after <<<