From 6fd42b4cb018ed867158bd766e5dddfa1e8ceb0c Mon Sep 17 00:00:00 2001
From: Alexander Plavin <alexander@plav.in>
Date: Wed, 7 Aug 2024 09:15:06 +0200
Subject: [PATCH] add changes()

---
 src/Observables.jl | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/Observables.jl b/src/Observables.jl
index 47af289..514cbd8 100644
--- a/src/Observables.jl
+++ b/src/Observables.jl
@@ -1,6 +1,6 @@
 module Observables
 
-export Observable, on, off, onany, connect!, obsid, async_latest, throttle
+export Observable, on, off, onany, connect!, obsid, async_latest, throttle, changes
 export Consume, ObserverFunction, AbstractObservable
 
 import Base.Iterators.filter
@@ -572,6 +572,23 @@ Observable(3)
     return obs
 end
 
+"""
+     changes(obs)
+
+Returns an `Observable` that only forwards `obs` updates when its value changes.
+"""
+function changes(obs::AbstractObservable{T}) where {T}
+	result = Observable{T}(obs[])
+    oldobs = Observable{T}(obs[])
+	on(obs) do val
+		if val != oldobs[]
+			result[] = val
+			oldobs[] = val
+		end
+	end
+	return result
+end
+
 
 """
     async_latest(observable::AbstractObservable, n=1)