Sometimes you want to execute some code in Swift 3 whenever a variable changes its value. And perhaps you’ve done this previously by creating a function that you call whenever it makes sense in your code.

However, there’s a MUCH better way!

We’ll learn how to use observers which act like watchdogs – they bark whenever even the tiniest part of a variable changes!

Declare a variable and implement the didSet function:


There are also other functions you can override in there, such as willSet, called BEFORE the variable is actually changed:


You can even stack these:

Of course there are many more functions you can override so I dare you to go look for them 😉


How to Observe Changes in Variables with Swift 4 and iOS 12
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