重复承诺，直到它没有被拒绝或达到超时[重复]-Java 学习之路

这个问题在这里已有答案：

Promise Retry Design Patterns 8个答案

我仍然是一个Promise noob，我正试图弄清楚如何让我的Promise重演 .

如果没有设置某个全局标志，则拒绝ES6 . 我需要它每500ms重试一次，直到：

承诺返回一个决心，
或达到最大尝试次数（假设为10） .

由于Promise是异步的，我真的不想使用 setInterval() 检查，因为我不能正确使用异步代码 . 一旦promise成功解决（或达到超时），我需要检查终止 .

我正在使用ES6 React ES6 Promises（所以请不要问Q或Bluebird特定的答案！）

// CLASS
class Test extends React.Component {
    constructor() {
      this.state = {
        status: 'setting up..',
      }
    }
    componentDidMount() {
      // TODO: how do I get this to loop with a timeout?
      this.createSlot()
        .then((slot) => {
          this.setState({
            status: slot
          });
        })
        .catch((e) => {
          this.setState({
            status: e.message
          });
        })
    }
    createSlot() {
      return new Promise((resolve, reject) => {
        if (!this.checkIsReady()) {
          reject(new Error('Global isnt ready yet'));
        }
        // more stuff here but going to resolve a string for simplicity sake
        resolve('successful!');
      });
    }
    checkIsReady() {
      return window.globalThing && window.globalThing === true;
    }
    render() {
        return ( <div>{this.state.status}</div> );
    }
}





    // RENDER OUT
    React.render(< Test/> , document.getElementById('container'));

EDIT: function based on current feedback:

createSlot(tries) {
    const _this = this;
    return new Promise(function cb(resolve, reject) {
      console.log(`${tries} remaining`);
      if (--tries > 0) {
        setTimeout(() => {
          cb(resolve, reject);
        }, 500);
      } else {
        const { divId, adUnitPath } = _this;
        const { sizes } = _this.props;

        // if it's not, reject
        if (!_this.isPubadsReady()) {
          reject(new Error('pubads not ready'));
        }
        // if it's there resolve
        window.googletag.cmd.push(() => {
          const slot = window.googletag
            .defineSlot(adUnitPath, sizes, divId)
            .addService(window.googletag.pubads());
          resolve(slot);
        });
      }
    });
  }

2 回答

正如Mike McCaughan所提到的，您可以使用 setTimeout 在两次尝试之间创建延迟 . 一旦成功或您的尝试用尽，请解决或拒绝您的承诺 .

function createPromise(tries, willFail) {
  return new Promise(function cb(resolve, reject) {
    console.log(tries + ' remaining');
    if (--tries > 0) {
      setTimeout(function() {
        cb(resolve, reject);
      }, 500);
    } else {
      if (willFail) {
        reject('Failure');
      } else {
        resolve('Success');
      }
    }
  });
}

// This one will fail after 3 attempts
createPromise(3, true)
  .then(msg => console.log('should not run'))
  .catch(msg => {
    console.log(msg);
    
    // This one will succeed after 5 attempts
    return createPromise(5, false);
  })
  .then(msg => console.log(msg))
  .catch(msg => console.log('should not run'));

回复于 2024-04-29T07:40:08+08:00

你可以尝试链接电话，因为承诺应该是，这有点做作但我希望你得到我的漂移：

PS将全局对象附加到窗口是一个坏主意，如果可能的话，不应该这样做，这只是显示使用您的流程的快速示例...

window.attempts = 0;
window.maxAttempts = 10;
window.globalThing = true;
function createSlot() {

return new Promise((resolve, reject) => {
    if (!this.checkIsReady()) {
      reject(new Error('Global isnt ready yet'));
    }
    // more stuff here but going to resolve a string for simplicity sake
    resolve('successful!');
}).then((pass) => {
    return pass;
  }, (fail) => {
    window.attempts ++;
    //If within attempts, try again
    if(window.attempts < window.maxAttempts){
      //Chain a new promise to resolve with a timeout of 500ms
      return new Promise((resolve, reject) => {
         setTimeout(() => {
            resolve()
         }, 500);
      }).then(() => {
         //Then try again
         return createSlot();
      })
    }
    else {
      //else fail out with reason
      return fail;
    }
  });
}

回复于 2024-04-29T07:40:08+08:00

重复承诺，直到它没有被拒绝或达到超时[重复]

2 回答

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