Question

我试图依次运行4个函数，我尝试了下面的代码，但是一些函数在运行第一个和第二个函数后如何卡住

代码示例：

const Bluebird = require('bluebird');

///// also tried changing all Bluebird below to Promise -> didn't work

//const Promise = require('bluebird');

const promisesFunc = async (array) => {
    let interval = 1000;
    const delayPromise1 = (data, delayDuration) => {
      return new Promise((resolve) => {
        setTimeout(() => {
            /// do some code here requires .map function may take 10s or more
            resolve();
        }, delayDuration)
      });
    };

    const delayPromise2 = (data, delayDuration) => {
      return new Promise((resolve) => {
        setTimeout(() => {
            /// do some code here requires .map function may take 10s or more
            resolve();
        }, delayDuration)
      });
    };

    const delayPromise3 = (data, delayDuration) => {
      return new Promise((resolve) => {
        setTimeout(() => {
            /// do some code here requires .map function may take 10s or more
            resolve();
        }, delayDuration)
      });
    };

    const delayPromise4 = (data, delayDuration) => {
      return new Promise((resolve) => {
        setTimeout(() => {
            /// do some code here requires .map function may take 10s or more
            resolve();
        }, delayDuration)
      });
    };

    try {
    /////////////// first attempt //////////////
    await Bluebird.map(array, (data, index) => delayPromise1(data, index * interval))
    await Bluebird.map(array, (data, index) => delayPromise2(data, index * interval))
    await Bluebird.map(array, (data, index) => delayPromise3(data, index * interval))
    await Bluebird.map(array, (data, index) => delayPromise4(data, index * interval))
    console.log('done ***************************************************');
    setTimeout(() => {
      console.log('response was sent');
      res.status(200).json('done')
    }, 1000);

    /////////////// second attempt ////////////

    const promises = Bluebird.map(array, (data, index) => delayPromise1(data, index * interval))
      .then(() => Bluebird.map(array, (data, index) => delayPromise2(data, index * interval)))
      .then(() => Bluebird.map(array, (data, index) => delayPromise3(data, index * interval)))
      .then(() => Bluebird.map(array, (data, index) => delayPromise4(data, index * interval)))
      .then(() => {
        setTimeout(() => {
          console.log('response was sent');
          res.status(200).json('done')
        }, 1000);
      })
      .catch(err => console.error(err))

      await Promise.all([promises]);

      ///////////// third attempt ////////////////////

      const promises1 = array.map((data, index) => delayPromise1(data, index * interval));
      const promises2 = array.map((data, index) => delayPromise2(data, index * interval));
      const promises3 = array.map((data, index) => delayPromise3(data, index * interval));
      const promises4 = array.map((data, index) => delayPromise4(data, index * interval));
      await Promise.all([promises1, promises2, promises3, promises4]);
      setTimeout(function(){
        console.log('response was sent');
        res.status(200).json('done')
      }, 1000);


    } catch (e) {
      console.error(e);
    }
}
promisesFunc(array)

注意，在第一次和第二次尝试中，delayPromise1和delayPromise2函数成功运行，但随后停止并且不再继续，其他解决方案分别不起作用

知道为什么会这样，还有没有更好的解决方案来保证这些功能分别运行。

需要这样的

PS 功能结构。并且它们需要分别一个接一个地运行。

映射一个数据数组，然后在delayPromise函数中对其进行一些处理，然后进行resolve（）。解决promise不必在某些情况下等待代码执行完成。

Answer 1

您的第三次尝试是要走的路。但是您可以在Promise.all解决并且所有异步操作完成后发送响应。

const promises1 = array.map((data, index) => delayPromise1(data, index * interval));
const promises2 = array.map((data, index) => delayPromise2(data, index * interval));
const promises3 = array.map((data, index) => delayPromise3(data, index * interval));
const promises4 = array.map((data, index) => delayPromise4(data, index * interval));

await Promise.all([promises1, promises2, promises3, promises4]).then(() => {
  console.log('response was sent');
  return res.status(200).json('done')
})

Answer 2

如果要并行运行，则所有延迟函数都在Glide.with(context) .load(gifUrl) .into(yourImageView)内部传递。如果要顺序运行，请使用如下所示。

Promise.all

Answer 3

我将像这样使用数组.reduce方法：

[delayPromise1, delayPromise2, ...]
    .reduce((m, delayPromise) => {

        /* here we chain the promises */
        return Promise.resolve(m).then(delayPromise)

    }, {/* any input data to be the argument of delayPromise1 */} )

    .then( res => {

        // do something when all is ready
    })

使用诺言时如何分别运行多个功能？

3 个答案: