fix: fix UniqueBy bug

slice/slice.go

@@ -783,17 +783,25 @@ func Unique[T comparable](slice []T) []T {
 	return result
 }
 
-// UniqueBy call iteratee func with every item of slice, then remove duplicated.
-// Play: https://go.dev/play/p/UR323iZLDpv
-func UniqueBy[T comparable](slice []T, iteratee func(item T) T) []T {
-	result := []T{}
+// UniqueBy removes duplicate elements from the input slice based on the values returned by the iteratee function.
+// The function maintains the order of the elements.
+// Play: todo
+func UniqueBy[T any, U comparable](slice []T, iteratee func(item T) U) []T {
+	result := make([]T, 0, len(slice))
+	seen := make(map[U]struct{}, len(slice))
 
-	for _, v := range slice {
-		val := iteratee(v)
-		result = append(result, val)
+	for i := range slice {
+		key := iteratee(slice[i])
+		if _, ok := seen[key]; ok {
+			continue
+		}
+
+		seen[key] = struct{}{}
+
+		result = append(result, slice[i])
 	}
 
-	return Unique(result)
+	return result
 }
 
 // UniqueByField remove duplicate elements in struct slice by struct field.

slice/slice_example_test.go

@@ -777,7 +777,7 @@ func ExampleUniqueBy() {
 	fmt.Println(result)
 
 	// Output:
-	// [1 2 0]
+	// [1 2 3]
 }
 
 func ExampleUniqueByField() {

slice/slice_test.go

@@ -733,7 +733,8 @@ func TestUniqueBy(t *testing.T) {
 	actual := UniqueBy([]int{1, 2, 3, 4, 5, 6}, func(val int) int {
 		return val % 4
 	})
-	assert.Equal([]int{1, 2, 3, 0}, actual)
+
+	assert.Equal([]int{1, 2, 3, 4}, actual)
 }
 
 func TestUniqueByField(t *testing.T) {