From 39453c20cba870c331be05eb68045ebcee24853b Mon Sep 17 00:00:00 2001
From: Yakir Gagnon <12.yakir@gmail.com>
Date: Fri, 6 May 2022 11:28:25 +0200
Subject: [PATCH 1/2] add onall

---
 Project.toml       |  2 +-
 src/Observables.jl | 34 +++++++++++++++++++++++++++++++++-
 test/runtests.jl   | 19 ++++++++++++++++---
 3 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/Project.toml b/Project.toml
index d410640..ba0890f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "Observables"
 uuid = "510215fc-4207-5dde-b226-833fc4488ee2"
-version = "0.5.1"
+version = "0.5.2"
 
 [compat]
 julia = "1.6"
diff --git a/src/Observables.jl b/src/Observables.jl
index 31da44d..90e8459 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, onall, connect!, obsid, async_latest, throttle
 export Consume, ObserverFunction, AbstractObservable
 
 import Base.Iterators.filter
@@ -348,6 +348,38 @@ function onany(f, args...; weak::Bool = false, priority::Int=0)
     return obsfuncs
 end
 
+
+onall(f) = error("onall needs at least two observables")
+onall(f, obs1) = error("onall needs at least two observables")
+
+"""
+    onall(f, args...)
+
+Calls `f` on updates to all observable refs in `args`.
+`f` is called only if all (i.e. not any) observable refs in `args` are updated at least once.
+`args` may contain any number of `Observable` objects.
+`f` will be passed the values contained in the refs as the respective argument.
+All other objects in `args` are passed as-is.
+
+See also: [`on`](@ref).
+"""
+function onall(f, observables...; condition=(old, new)-> true)
+    updated = fill(false, length(observables))
+    for (i, observable) in enumerate(observables)
+        old = observable[]
+        on(observable) do new_value
+            if condition(old, new_value)
+                updated[i] = true
+                if all(updated)
+                    f(to_value.(observables)...)
+                    fill!(updated, false)
+                end
+            end
+            old = new_value
+        end
+    end
+end
+
 """
     map!(f, observable::AbstractObservable, args...; update::Bool=true)
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 6c7bd52..0901c7b 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -167,7 +167,7 @@ end
     r[] = 3 # shouldn't call test
 end
 
-@testset "onany and map" begin
+@testset "onany, onall, and map" begin
     r = Observable(0)
     tested = Ref(false)
     onany(1, r) do x, y
@@ -178,6 +178,19 @@ end
     r[] = 2
     @test tested[]
 
+    r1 = Observable(0)
+    r2 = Observable(0)
+    tested = Ref(false)
+    onall(r1, r2) do x, y
+        @test x == 1
+        @test y == 2
+        tested[] = true
+    end
+    r1[] = 1
+    @test !tested[]
+    r2[] = 2
+    @test tested[]
+
     r1 = Observable(0)
     r2 = Observable(0)
     map!(x->x+1, r2, r1)
@@ -339,14 +352,14 @@ end
 
     o = Observable(0)
     cnt[] = 0
-    function compute_something(x)
+    function compute_something_else(x)
         for i=1:10^8; rand() end
         cnt[] = cnt[] + 1
     end
     sleep(1)
     o_latest = async_latest(o, 3)
 
-    on(compute_something, o_latest) # compute something on the latest update
+    on(compute_something_else, o_latest) # compute something on the latest update
     for i=1:5
         o[] = i
     end

From 6495575d8b64ab57d5fe23049456d09dce2fbd0a Mon Sep 17 00:00:00 2001
From: Yakir Luc Gagnon <12.yakir@gmail.com>
Date: Sun, 8 May 2022 09:06:54 +0200
Subject: [PATCH 2/2] Update src/Observables.jl

Co-authored-by: Anshul Singhvi <anshulsinghvi@gmail.com>
---
 src/Observables.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Observables.jl b/src/Observables.jl
index 90e8459..1c0cfda 100644
--- a/src/Observables.jl
+++ b/src/Observables.jl
@@ -356,7 +356,7 @@ onall(f, obs1) = error("onall needs at least two observables")
     onall(f, args...)
 
 Calls `f` on updates to all observable refs in `args`.
-`f` is called only if all (i.e. not any) observable refs in `args` are updated at least once.
+`f` is called only if *all* (as opposed to any) observable refs in `args` are updated at least once.
 `args` may contain any number of `Observable` objects.
 `f` will be passed the values contained in the refs as the respective argument.
 All other objects in `args` are passed as-is.