如何实现承诺

Question

I have a question regarding chaining promise.

Here's my code:

var removeProducts = function(id) {
    anotherService.removeProducts(id); // this will return a promise.
}

var addProduct = function(id) {
    myService.addProduct({id: id})
}

$scope.pickProduct = function() {
    myService.updateId({'id':123}).$promise.then(function(items) {
        items.categories.filter(function(category) {
            if (category.type === 'NEW') {
               removeProducts(items.id);
            }
        })
        //this is the part I don't know how to proceed. I need to make sure 
        //the product is removed before first and update ID second so I can add     
        //another product.  

        addProduct(item.id);
    })
}

Basically I need to call the updateId method from myService every time I add or remove a product. So the steps are as follows:

Update ID
Remove product if there is a type 'New'
Update ID 
Add product

How do I change this? Thanks for the help!

Answer 1

call the updateID function in the then returned from the removeProduct. Like this:

$scope.pickProduct = function() {
  myService.updateId({
    'id': 123
  }).$promise.then(function(items) {
    items.categories.filter(function(category) {
      if (category.type === 'NEW') {
        removeProducts(items.id).then(function() {
            //call updateId .then(function(){
            // call add product
          }
        };
      }
    })
  })
}

Answer 2

Basically you can chain promise like that:

myService.pickProduct(product)
    .then(_update)
    .then(_remove)
    .then(_add)
    .catch(..);



function _update(product) {
    return product.id;
}

function _remove(id) {
   return new Date();
}

function _add(date) {

}

The return value of a then will be the input of the next 'chain' promise then . In my case the service function pickProduct has to return a promise that holds the product, because I expect it as input within _update and so on.