添加 IfThenElse 函数返回泛型结果 (#259)

* update
1. 增加了一个条件判断返回泛型结果的函数；
1. 增加了一个条件判断执行对应方法的函数；
2. 调整和增加单元测试和Example；

* IfThenElseFunc固定增加错误返回，泛型T作为用户可以自定义返回的结果

---------

Co-authored-by: huangdawei <[email protected]>

condition.go

@@ -0,0 +1,32 @@
+// Copyright 2021 ecodeclub
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ekit
+
+// IfThenElse 根据条件返回对应的泛型结果
+// 注意避免结果的空指针问题
+func IfThenElse[T any](condition bool, trueValue, falseValue T) T {
+	if condition {
+		return trueValue
+	}
+	return falseValue
+}
+
+// IfThenElseFunc 根据条件执行对应的函数并返回泛型结果
+func IfThenElseFunc[T any](condition bool, trueFunc, falseFunc func() (T, error)) (T, error) {
+	if condition {
+		return trueFunc()
+	}
+	return falseFunc()
+}

condition_test.go

@@ -0,0 +1,65 @@
+// Copyright 2021 ecodeclub
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ekit
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIfThenElse(t *testing.T) {
+	i := 7
+	i = IfThenElse(false, i, 0)
+	assert.Equal(t, i, 0)
+}
+
+func ExampleIfThenElse() {
+	result := IfThenElse(true, "yes", "no")
+	fmt.Println(result)
+
+	// Output:
+	// yes
+}
+
+func TestIfThenElseFunc(t *testing.T) {
+	resp, err := IfThenElseFunc(true, func() (int, error) {
+		return 0, nil
+	}, func() (int, error) {
+		return 1, errors.New("some error")
+	})
+	assert.NoError(t, err)
+	assert.Equal(t, resp, 0)
+}
+
+func ExampleIfThenElseFunc() {
+	code, err := IfThenElseFunc(false, func() (code int, err error) {
+		// do something when condition is true
+		// ...
+		return 0, nil
+	}, func() (code int, err error) {
+		// do something when condition is false
+		// ...
+		return 1, errors.New("some error when execute func2")
+	})
+	fmt.Println(code)
+	fmt.Println(err)
+
+	// Output:
+	// 1
+	// some error when execute func2
+}