From 52ea64bc334231c61b1322b2f7b495ba10dd599e Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Mon, 17 Apr 2023 20:17:26 +0800
Subject: [PATCH] feat: add FindLastBy function

---
 slice/slice.go              | 20 ++++++++++++++++++++
 slice/slice_example_test.go | 17 +++++++++++++++++
 slice/slice_test.go         | 19 +++++++++++++++++++
 3 files changed, 56 insertions(+)

diff --git a/slice/slice.go b/slice/slice.go
index 5837575..e683026 100644
--- a/slice/slice.go
+++ b/slice/slice.go
@@ -367,6 +367,26 @@ func FindBy[T any](slice []T, predicate func(index int, item T) bool) (v T, ok b
 	return slice[index], true
 }
 
+// FindLastBy iterates over elements of slice, returning the last one that passes a truth test on predicate function.
+// If return T is nil or zero value then no items matched the predicate func.
+// In contrast to Find or FindLast, its return value no longer requires dereferencing
+func FindLastBy[T any](slice []T, predicate func(index int, item T) bool) (v T, ok bool) {
+	index := -1
+
+	for i := len(slice) - 1; i >= 0; i-- {
+		if predicate(i, slice[i]) {
+			index = i
+			break
+		}
+	}
+
+	if index == -1 {
+		return v, false
+	}
+
+	return slice[index], true
+}
+
 // Flatten flattens slice with one level.
 // Play: https://go.dev/play/p/hYa3cBEevtm
 func Flatten(slice any) any {
diff --git a/slice/slice_example_test.go b/slice/slice_example_test.go
index 347eb93..9d94ebe 100644
--- a/slice/slice_example_test.go
+++ b/slice/slice_example_test.go
@@ -358,6 +358,23 @@ func ExampleFindBy() {
 	// true
 }
 
+func ExampleFindLastBy() {
+	nums := []int{1, 2, 3, 4, 5}
+
+	isEven := func(i, num int) bool {
+		return num%2 == 0
+	}
+
+	result, ok := FindLastBy(nums, isEven)
+
+	fmt.Println(result)
+	fmt.Println(ok)
+
+	// Output:
+	// 4
+	// true
+}
+
 func ExampleFlatten() {
 	arrs := [][][]string{{{"a", "b"}}, {{"c", "d"}}}
 
diff --git a/slice/slice_test.go b/slice/slice_test.go
index c717e03..32c5c8a 100644
--- a/slice/slice_test.go
+++ b/slice/slice_test.go
@@ -268,6 +268,25 @@ func TestFindBy(t *testing.T) {
 	assert.Equal(res == 0 && ok == false, true)
 }
 
+func TestFindLastBy(t *testing.T) {
+	assert := internal.NewAssert(t, "TestFindBy")
+
+	nums := []int{1, 2, 3, 4, 5}
+	even := func(i, num int) bool {
+		return num%2 == 0
+	}
+	res, ok := FindLastBy(nums, even)
+	if !ok {
+		t.Fatal("found nothing")
+	}
+	assert.Equal(4, res)
+
+	res, ok = FindLastBy(nums, func(_ int, v int) bool {
+		return v == 6
+	})
+	assert.Equal(res == 0 && ok == false, true)
+}
+
 func TestFindLast(t *testing.T) {
 	nums := []int{1, 2, 3, 4, 5}
 	even := func(i, num int) bool {