@Concurrent Decorator: Declaring and Verifying Concurrent Functions

To pass function verification, the concurrent functions executed in a TaskPool must be decorated using @Concurrent.

NOTE

Since API version 9, this decorator is supported in ArkTS widgets.

Decorator Description

NOTE

Pay attention to the performance of returning Promise in the concurrent function. The concurrent synchronous function processes and returns Promise with the result.

Example

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();

The output is as follows:

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

NOTE

If Promise is used in the concurrent asynchronous function, you are advised to use await to capture exceptions that may occur in Promise. A recommended example is provided below.

Example

@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()

The output is as follows:

task1 catch e: Error: testPromise Error
task2 catch e: testPromiseError1 Error msg
task3 catch e: testPromiseError2 Error msg

Example

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%')
  }
}