使用Angular的resolve：时，兑现承诺的最佳方法是什么？

Question

I am using angular's resolve and would like to chain two promises. What is the best way of going about this? In essence, I want:

resolve: {
    my_two_lists: function() {
    return MyService.list().then(function(array1) {     
         return MyOtherService.list().then(function(array2) { 
               return new Promise(function(resolve, reject) { 
                    resolve(array1.concat(array2)); 
               }); 
          }); 
       });
    }
}

In other words: I have 2 services, each with two methods called "list" that return, well, a promise which resolve to lists. I would like to chain the two resulting promises.

Answer 1

Something I've learned with Javascript promises - if you have more than one level of nesting, there will be a better way.

Here's a cleaner solution where you invoke the two list commands in parralel.

resolve: {
    my_two_lists: function() {
            return Promise.all([MyService.list(), MyOtherService.list()])
                   .then(function(values) {
                        return values[0].concat(values[1]));
                   });
    }
}

If, for some reason, you wanted to call them one after the other, then your example is correct, except there's no need to return yet another promise. Just return a value. The result of my_two_lists will still be a promise that resolves to the concatenation of the two arrays.

resolve: {
    my_two_lists: function() {
    return MyService.list().then(function(array1) {     
         return MyOtherService.list().then(function(array2) { 
               return array1.concat(array2);
          }); 
       });
    }
}