循环调用API-Angular js

Question

I have a set of APIs which I have to run inside a for loop

for(var i=0; i<array.length; i++ )
    service.getfunction(array[i]).then(function(response) {
      service.getfunction1(response).then(function(response) {
        service.getfunction2(response).then(function(response) {
          service.getfunction3(response).then(function(response) {
             console.log(response);
          });
        });
      });
    });
)

Second loop should start only after I got result from last getfunction3 API for first loop. How can I do this?

Answer 1

First of all - you can chain your promises like:

function doJob(i) {
  return service.getfunction(array[i]).then(function(response) {
    return service.getfunction1(response);
  }).then(function(response) {
    return service.getfunction2(response);
  }).then(function(response) {
    return service.getfunction3(response);
  }).then(function(response) {
    console.log(response);
  });
}

This function will return promise that will be resolved once all this service calls done. And now lets use it:

var p = Promise.resolve(true);
for(var i = 0; i < array.length; i++) {
  (function(idx) { //We need to wrap it or we will pass incorrect i into doJob
    p = p.then(function() {
      return doJob(idx);
    });
  })(i);
}
p.then(function() {
  console.log('Everything done');
});

Answer 2

Wrap it in a function:

// Declare function 
function LoopAPI() {
    for(var i=0; i<array.length; i++ )
        service.getfunction(array[i]).then(function(response) {
          service.getfunction1(response).then(function(response) {
            service.getfunction2(response).then(function(response) {
              service.getfunction3(response).then(function(response) {
                 console.log(response);

                 // Call function again
                 LoopAPI();
              });
            });
          });
        });
    )
}

// First call
LoopAPI();

Answer 3

You can chain promises then use Array.reduce to call them in order as such:

array.reduce(function(previous, next)
{
    return previous.then(function()
    {
        return service.getfunction(next);
    })
    .then(function(response)
    {
        return service.getfunction1(response);
    })
    .then(function(response)
    {
        return service.getfunction2(response);
    })
    .then(function(response)
    {
        return service.getfunction3(response);
    });
}, Promise.resolve())
.then(function()
{
    console.log("All done.");
})
.catch(function(error)
{
    console.log(error);
});