使用 for 循环的 promise 内的 promise

Question

I want to call multiple api, the second api need something from the first api, I created two promise but now I'm stuck, how can I execute what needs to be done and wait all of them finish?

createAccount(this.state.item) //promise
.then(resp=>{

  this.state.albums.forEach(o=>{ //array of object
    createAlbum(resp.id, { //promise
      ...o
    })
  })
})

I'm using bluebird I got a hint, using promise.all but I have no clue how that work with forEach, I can't control how many albums are there.

Answer 1

It sounds like you want to create the account, then create some number of albums stored in an array. This is indeed exactly what Promise.all would be for:

createAccount(this.state.item)
.then(resp =>
    Promise.all(
        this.state.albums.map(o => createAlbum(resp.id, o))
    )
);

You'll need to either return the promise created by then to the caller, or handle errors on it (eg, via .catch ), as is always the case with promises.

More about Promise.all in the bluebird docs and on MDN .

Answer 2

It is not clear what you want but if you want to process each album you can use Promise.all with Array.prototype.map Your code will look something like this:

//if this is part of a function you shoud
// return createAccount ...
createAccount(this.state.item) //promise
.then(
  resp=>//arrow function without {} will return first statement
        //resp=>Promise.all(... is same as resp=>{ return Promise.all(...
    Promise.all(
      this.state.albums.map(
        album=>{
          //not sure why you want to keep calling createAlbum
          //  but only have one id, did you want to do album.id?
          createAlbum(resp.id)
          .then(
            o=>{
              //do something with o, album or response, they are all available
              return album;//you acn for example return album
            }
          )
        }
      )  
    )
)
.then(
  results=>{
    //results is an array of whatever o=> returns
  }
).catch(
  error=>{
    console.warn("something went wrong:",error);
  }
);

Please let me know if you have any questions, will probably need:

1. The code you are using
2. Add some console.log("album is:",JSON.stringify(album,undefined,2) statements in the code (album is an example). So you can debug some of the code yourself and identify if the data objects you think you have are actually the object you have.
3. Any errors that you have. Press F12 in browser and look at console and network tab. The console will show errors and your console.logs and network will show your xhr with the errors/response.

Answer 3

Use promise.map instead of promise.all, find example below for reference-

Promise.map(this.state.albums, function(fileName) {
    // Promise.map awaits for returned promises as well.
    return x;
}).then(function() {
    console.log("Done");
});