From c25a68894f3bce8a8e63289b46ecd6e29f5cc227 Mon Sep 17 00:00:00 2001 From: Sam Anthony Date: Thu, 22 Aug 2024 21:26:41 -0400 Subject: val: add TryGet() method --- val.go | 13 +++++++++++++ val_test.go | 24 ++++++++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/val.go b/val.go index 4d35fb9..2b762cb 100644 --- a/val.go +++ b/val.go @@ -47,6 +47,19 @@ func (v Val[T]) Get() T { return <-c } +// TryGet returns the stored value if it has already been set, or false if it hasn't. +func (v Val[T]) TryGet() (*T, bool) { + c := make(chan T) + defer close(c) + select { + case v.Request <- c: + val := <-c + return &val, true + default: + return nil, false + } +} + func (v Val[T]) Close() { close(v.Request) close(v.Set) diff --git a/val_test.go b/val_test.go index 188f8a8..c1b7766 100644 --- a/val_test.go +++ b/val_test.go @@ -34,6 +34,30 @@ func TestValSetRemote(t *testing.T) { <-done } +// Val.TryGet() before Set should fail. +func TestValTryGetFail(t *testing.T) { + sv := share.NewVal[int]() // type is arbitrary + defer sv.Close() + if v, ok := sv.TryGet(); ok { + t.Errorf("Val.TryGet() succeeded (returned %v) before value was set; expected to fail", v) + } +} + +// Val.TryGet() after Set should succeed. +func TestValTryGet(t *testing.T) { + sv := share.NewVal[string]() + defer sv.Close() + v := "foo" + sv.Set <- v + ret, ok := sv.TryGet() + if !ok { + t.Error("Val.TryGet() failed") + } + if *ret != v { + t.Errorf("Val.TryGet() returned %v; expected %v", ret, v) + } +} + func verifySameVal[T comparable](sv share.Val[T], v T, t *testing.T) { ret := sv.Get() if ret != v { -- cgit v1.2.3