如何在异步函数中重新组织我的收益? [英] How can I reorganize my return in an async function?

问题描述

假设我有一个函数，可以从数据库中获取一些数据.

 findById(id){返回Model.findById(id)} 

我需要重新组织用户数据的返回，如下所示:

  {名称:汤姆"，年龄:57} 

变成这样:

  {消息:成功找到用户"，成功:对，用户:user} 

到目前为止，我可以通过 Promise"then" 部分来进行管理，如下所示:

 返回Model.findById(id).then(user => {如果(！user){logger.warn(`找不到ID为$ {id}`的用户)；返回{消息:找不到ID为$ {id}的用户，成功:false，用户:null}；}返回{消息:`ID为$ {id}的用户，成功:true，用户:user}；}).catch(err => {如果(错误){logger.error(err.message);返回{消息:err.message，成功:否，用户:null}；}}) 

我可以对 async/await 进行同样的操作，并返回我的reorninazed返回吗?因为到目前为止，它从数据库返回了 user对象:

  async findById(id){返回等待this.model.findById(id，function(user，err){如果(错误){console.log('test');logger.error(err);返回{消息:err.message，成功:否，用户:null}；}如果(！user){logger.warn(`找不到ID为$ {id}`的用户)；返回{消息:找不到ID为$ {id}的用户，成功:false，用户:null}；}返回{消息:`ID为$ {id}的用户，成功:true，用户:user}；});} 

提前谢谢！

解决方案

大多数数据库API不同时支持回调和Promise.如果传递回调，则它们不会返回承诺.选择一种或另一种.您第一种使用 .then()的方法可以很好地工作，因为这都是基于promise的.

您的第二种方法不起作用，因为您要传递常规回调.这告诉数据库不要返回承诺，因为您使用的是较旧的回调样式，但是您尝试使用该承诺.

如果您想使用 async/await ，则可以这样操作:

  async findById(id){尝试 {让用户=等待this.model.findById(id);如果(用户){返回{消息:`ID为$ {id}的用户，成功:true，用户:user}；} 别的 {logger.warn(`找不到ID为$ {id}`的用户)；返回{消息:找不到ID为$ {id}的用户，成功:false，用户:null}；}} catch(e){logger.error(err);返回{消息:err.message，成功:否，用户:null}；}} 

仅供参考，您可以从第一个代码块中的 .catch()处理程序中删除 if(err)测试.如果触发了 .catch()，则出现错误-您无需测试是否存在该错误.

let's say I've got a function where I'm fetching for some data from a DB.

findById(id) {
    return Model.findById(id)
}

I need to reorganize the return from the user data like this:

{
   name: "Tom",
   age: 57
}

into something like this:

{
   message: "User is found successfully", 
   success: true, 
   user: user
}

So far I can manage with that with a Promise "then" section, like this:

return Model.findById(id)
      .then(user => {
        if (!user) {
          logger.warn(`Coundn't find user with id: ${id}`);
          return { message: `Coundn't find user with id: ${id}`, success: false, user: null };
        }
        return { message: `User with id: ${id}`, success: true, user: user };
      })
      .catch(err => {
        if (err) {
          logger.error(err.message);
          return { message: err.message, success: false, user: null };
        }
      })

Can I do the same with a async/await and return my reorninazed return? Because so far it returns the user object from the DB:

async findById(id) {

    return await this.model.findById(id, function (user, err) {
      if (err) {
        console.log('test');
        logger.error(err);
        return { message: err.message, success: false, user: null };
      }
      if (!user) {
        logger.warn(`Coundn't find user with id: ${id}`);
        return { message: `Coundn't find user with id: ${id}`, success: false, user: null };
      }
      return { message: `User with id: ${id}`, success: true, user: user };
    });
}

Thanks in advance!

解决方案

Most database APIs do NOT support both a callback and a promise at the same time. If you pass a callback, they do not return a promise. Pick one style or the other. Your first approach using .then() works just fine as that is all promise-based.

Your second approach does not work because you're passing a regular callback. That tells the database to NOT return a promise because you're using the older callback style, but you're trying to use that promise.

If you want to use async/await, you could do so like this:

async findById(id) {
    try {
        let user = await this.model.findById(id);
        if (user) {
            return { message: `User with id: ${id}`, success: true, user: user };
        } else {
            logger.warn(`Coundn't find user with id: ${id}`);
            return { message: `Coundn't find user with id: ${id}`, success: false, user: null };
        }
    } catch(e) {
        logger.error(err);
        return { message: err.message, success: false, user: null };
    }
}

FYI, you can remove the if (err) test in the .catch() handler from your first code block. If .catch() is triggered, there is an error - you don't need to test if one is there.

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