OpenHarmony-v4.1-Release/s

# \@Concurrent装饰器：声明并校验并发函数

在使用[TaskPool](../reference/apis-arkts/js-apis-taskpool.md)时，执行的并发函数需要使用该装饰器修饰，否则无法通过相关校验。


> **说明：**
>
> 从API version 9开始，该装饰器支持在ArkTS卡片中使用。


## 装饰器说明
| \@Concurrent并发装饰器 | 说明                                                                                       |
| --------------------- | ------------------------------------------------------------------------------------------ |
| 装饰器参数             | 无。                                                                                       |
| 使用场景               | 仅支持在Stage模型的工程中使用。                                                              |
| 装饰的函数类型         | 允许标注async函数或普通函数。禁止标注generator、箭头函数、method。不支持类成员函数或者匿名函数。  |
| 装饰的函数内的变量类型  | 允许使用local变量、入参和通过import引入的变量。禁止使用闭包变量。                               |
| 装饰的函数内的返回值类型  | 支持的类型请查[序列化支持类型](serialization-support-types.md)。    |

> **说明：**
>
> 并发函数中返回Promise的表现需关注，其中并发同步函数会处理返回该Promise并返回结果。

**示例：**

```ts
import taskpool from '@ohos.taskpool';

@Concurrent
function testPromise(args1: number, args2: number): Promise<number> {
  return new Promise<number>((testFuncA, testFuncB)=>{
    testFuncA(args1 + args2);
  });
}

@Concurrent
async function testPromise1(args1: number, args2: number): Promise<number> {
  return new Promise<number>((testFuncA, testFuncB)=>{
    testFuncA(args1 + args2);
  });
}

@Concurrent
async function testPromise2(args1: number, args2: number): Promise<number> {
  return await new Promise<number>((testFuncA, testFuncB)=>{
    testFuncA(args1 + args2)
  });
}

@Concurrent
function testPromise3() {
  return Promise.resolve(1);
}

@Concurrent
async function testPromise4(): Promise<number> {
  return 1;
}

@Concurrent
async function testPromise5(): Promise<string> {
  return await new Promise((resolve) => {
    setTimeout(()=>{
      resolve("Promise setTimeout after resolve");
    }, 1000)
  });
}

async function testConcurrentFunc() {
  let task1: taskpool.Task = new taskpool.Task(testPromise, 1, 2);
  let task2: taskpool.Task = new taskpool.Task(testPromise1, 1, 2);
  let task3: taskpool.Task = new taskpool.Task(testPromise2, 1, 2);
  let task4: taskpool.Task = new taskpool.Task(testPromise3);
  let task5: taskpool.Task = new taskpool.Task(testPromise4);
  let task6: taskpool.Task = new taskpool.Task(testPromise5);

  taskpool.execute(task1).then((d:object)=>{
    console.info("task1 res is: " + d)
  }).catch((e:object)=>{
    console.info("task1 catch e: " + e)
  })
  taskpool.execute(task2).then((d:object)=>{
    console.info("task2 res is: " + d)
  }).catch((e:object)=>{
    console.info("task2 catch e: " + e)
  })
  taskpool.execute(task3).then((d:object)=>{
    console.info("task3 res is: " + d)
  }).catch((e:object)=>{
    console.info("task3 catch e: " + e)
  })
  taskpool.execute(task4).then((d:object)=>{
    console.info("task4 res is: " + d)
  }).catch((e:object)=>{
    console.info("task4 catch e: " + e)
  })
  taskpool.execute(task5).then((d:object)=>{
    console.info("task5 res is: " + d)
  }).catch((e:object)=>{
    console.info("task5 catch e: " + e)
  })
  taskpool.execute(task6).then((d:object)=>{
    console.info("task6 res is: " + d)
  }).catch((e:object)=>{
    console.info("task6 catch e: " + e)
  })
}

testConcurrentFunc();
```

输出结果如下所示：
```
task1 res is: 3
task2 catch e: Error: Can't return Promise in pending state
task3 res is: 3
task4 res is: 1
task5 res is: 1
task6 res is: Promise setTimeout after resolve
```

> **说明：**
>
> 并发异步方法中如果使用Promise，建议搭配await使用捕获Promise中可能发生的异常。推荐使用示例如下。

**示例：**

```ts
@Concurrent
async function testPromiseError() {
  await new Promise<number>((resolve, reject) => {
    resolve(1);
  }).then(()=>{
    throw new Error("testPromise Error");
  })
}

@Concurrent
async function testPromiseError1() {
  await new Promise<string>((resolve, reject) => {
    reject("testPromiseError1 Error msg");
  })
}

@Concurrent
function testPromiseError2() {
  return new Promise<string>((resolve, reject) => {
    reject("testPromiseError2 Error msg");
  })
}

async function testConcurrentFunc() {
  let task1: taskpool.Task = new taskpool.Task(testPromiseError);
  let task2: taskpool.Task = new taskpool.Task(testPromiseError1);
  let task3: taskpool.Task = new taskpool.Task(testPromiseError2);

  taskpool.execute(task1).then((d:object)=>{
    console.info("task1 res is: " + d)
  }).catch((e:object)=>{
    console.info("task1 catch e: " + e)
  })
  taskpool.execute(task2).then((d:object)=>{
    console.info("task2 res is: " + d)
  }).catch((e:object)=>{
    console.info("task2 catch e: " + e)
  })
  taskpool.execute(task3).then((d:object)=>{
    console.info("task3 res is: " + d)
  }).catch((e:object)=>{
    console.info("task3 catch e: " + e)
  })
}

testConcurrentFunc()
```

输出结果如下所示：
```
task1 catch e: Error: testPromise Error
task2 catch e: testPromiseError1 Error msg
task3 catch e: testPromiseError2 Error msg
```


## 装饰器使用示例
  ```ts
  import taskpool from '@ohos.taskpool';

  @Concurrent
  function add(num1: number, num2: number): number {
    return num1 + num2;
  }

  async function ConcurrentFunc(): Promise<void> {
    try {
      let task: taskpool.Task = new taskpool.Task(add, 1, 2);
      console.info("taskpool res is: " + await taskpool.execute(task));
    } catch (e) {
      console.error("taskpool execute error is: " + e);
    }
  }

  @Entry
  @Component
  struct Index {
    @State message: string = 'Hello World'

    build() {
      Row() {
        Column() {
          Text(this.message)
            .fontSize(50)
            .fontWeight(FontWeight.Bold)
            .onClick(() => {
              ConcurrentFunc();
            })
        }
        .width('100%')
      }
      .height('100%')
    }
  }
  ```