slice: 增加函数ToMap, ToMapV (#249)

* update rand code

* update rand code

* update comments

* update changelog

* update error

* reverse支持所有type, 修改internal slice的作用范围

* update comments

* update List method defination

* update comments

* 增加两个func MapWithE2KFunc, MapWithE2KVFunc

* update

* fix comments

slice/map.go

@@ -36,6 +36,57 @@ func Map[Src any, Dst any](src []Src, m func(idx int, src Src) Dst) []Dst {
 	return dst
 }
 
+// 将[]Ele映射到map[Key]Ele
+// 从Ele中提取Key的函数fn由使用者提供
+//
+// 注意:
+// 如果出现 i < j
+// 设：
+//
+//	key_i := fn(elements[i])
+//	key_j := fn(elements[j])
+//
+// 满足key_i == key_j 的情况，则在返回结果的resultMap中
+// resultMap[key_i] = val_j
+//
+// 即使传入的字符串为nil，也保证返回的map是一个空map而不是nil
+func ToMap[Ele any, Key comparable](
+	elements []Ele,
+	fn func(element Ele) Key,
+) map[Key]Ele {
+	return ToMapV(
+		elements,
+		func(element Ele) (Key, Ele) {
+			return fn(element), element
+		})
+}
+
+// 将[]Ele映射到map[Key]Val
+// 从Ele中提取Key和Val的函数fn由使用者提供
+//
+// 注意:
+// 如果出现 i < j
+// 设：
+//
+//	key_i, val_i := fn(elements[i])
+//	key_j, val_j := fn(elements[j])
+//
+// 满足key_i == key_j 的情况，则在返回结果的resultMap中
+// resultMap[key_i] = val_j
+//
+// 即使传入的字符串为nil，也保证返回的map是一个空map而不是nil
+func ToMapV[Ele any, Key comparable, Val any](
+	elements []Ele,
+	fn func(element Ele) (Key, Val),
+) (resultMap map[Key]Val) {
+	resultMap = make(map[Key]Val, len(elements))
+	for _, element := range elements {
+		k, v := fn(element)
+		resultMap[k] = v
+	}
+	return
+}
+
 // 构造map
 func toMap[T comparable](src []T) map[T]struct{} {
 	var dataMap = make(map[T]struct{}, len(src))

slice/map_test.go

@@ -101,3 +101,248 @@ func ExampleFilterMap() {
 	fmt.Println(dst)
 	// Output: [1 3]
 }
+
+func TestToMapV(t *testing.T) {
+	t.Run("integer-string to map[int]int", func(t *testing.T) {
+		elements := []string{"1", "2", "3", "4", "5"}
+		resMap := ToMapV(elements, func(str string) (int, int) {
+			num, _ := strconv.Atoi(str)
+			return num, num
+		})
+		epectedMap := map[int]int{
+			1: 1,
+			2: 2,
+			3: 3,
+			4: 4,
+			5: 5,
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+	t.Run("struct<string, string, int> to map[string]struct<string, string, int>", func(t *testing.T) {
+		type eleType struct {
+			A string
+			B string
+			C int
+		}
+		elements := []eleType{
+			{
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			{
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		resMap := ToMapV(elements, func(ele eleType) (string, eleType) {
+			return ele.A, ele
+		})
+		epectedMap := map[string]eleType{
+			"a": {
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			"c": {
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+
+	t.Run("struct<string, string, int> to map[string]struct<string, string, int>, 重复的key", func(t *testing.T) {
+		type eleType struct {
+			A string
+			B string
+			C int
+		}
+		elements := []eleType{
+			{
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			{
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+			{
+				A: "a",
+				B: "d",
+				C: 3,
+			},
+		}
+		resMap := ToMapV(elements, func(ele eleType) (string, eleType) {
+			return ele.A, ele
+		})
+		epectedMap := map[string]eleType{
+			"a": {
+				A: "a",
+				B: "d",
+				C: 3,
+			},
+			"c": {
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+
+	t.Run("传入nil slice,返回空map", func(t *testing.T) {
+		var elements []string = nil
+		resMap := ToMapV(elements, func(str string) (int, int) {
+			num, _ := strconv.Atoi(str)
+			return num, num
+		})
+		epectedMap := make(map[int]int)
+		assert.Equal(t, epectedMap, resMap)
+	})
+}
+
+func TestToMap(t *testing.T) {
+	t.Run("integer-string to map[int]string", func(t *testing.T) {
+		elements := []string{"1", "2", "3", "4", "5"}
+		resMap := ToMap(elements, func(str string) int {
+			num, _ := strconv.Atoi(str)
+			return num
+		})
+		epectedMap := map[int]string{
+			1: "1",
+			2: "2",
+			3: "3",
+			4: "4",
+			5: "5",
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+	t.Run("struct<string, string, int> to map[string]struct<string, string, int>", func(t *testing.T) {
+		type eleType struct {
+			A string
+			B string
+			C int
+		}
+		elements := []eleType{
+			{
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			{
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		resMap := ToMap(elements, func(ele eleType) string {
+			return ele.A
+		})
+		epectedMap := map[string]eleType{
+			"a": {
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			"c": {
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+
+	t.Run("struct<string, string, int> to map[string]struct<string, string, int>, 重复的key", func(t *testing.T) {
+		type eleType struct {
+			A string
+			B string
+			C int
+		}
+		elements := []eleType{
+			{
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			{
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		resMap := ToMap(elements, func(ele eleType) string {
+			return ele.A
+		})
+		epectedMap := map[string]eleType{
+			"a": {
+				A: "a",
+				B: "b",
+				C: 1,
+			},
+			"c": {
+				A: "c",
+				B: "d",
+				C: 2,
+			},
+		}
+		assert.Equal(t, epectedMap, resMap)
+	})
+
+	t.Run("传入nil slice,返回空map", func(t *testing.T) {
+		var elements []string = nil
+		resMap := ToMap(elements, func(str string) int {
+			num, _ := strconv.Atoi(str)
+			return num
+		})
+		epectedMap := make(map[int]string)
+		assert.Equal(t, epectedMap, resMap)
+	})
+}
+
+func ExampleToMap() {
+	elements := []string{"1", "2", "3", "4", "5"}
+	resMap := ToMap(elements, func(str string) int {
+		num, _ := strconv.Atoi(str)
+		return num
+	})
+	fmt.Println(resMap)
+	// Output: map[1:1 2:2 3:3 4:4 5:5]
+}
+
+func ExampleToMapV() {
+	type eleType struct {
+		A string
+		B string
+		C int
+	}
+	type eleTypeOut struct {
+		A string
+		B string
+	}
+	elements := []eleType{
+		{
+			A: "a",
+			B: "b",
+			C: 1,
+		},
+		{
+			A: "c",
+			B: "d",
+			C: 2,
+		},
+	}
+	resMap := ToMapV(elements, func(ele eleType) (string, eleTypeOut) {
+		return ele.A, eleTypeOut{
+			A: ele.A,
+			B: ele.B,
+		}
+	})
+	fmt.Println(resMap)
+	// Output: map[a:{a b} c:{c d}]
+}