current community

your communities

more stack exchange communities

company blog
Stack Exchange Inbox Reputation and Badges
tour help
stack overflow careers
Sign up ×
Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute:
up vote 2 down vote favorite
1

I need to append the necessary HMAC headers to a request. This should not be very difficult however I am starting to get frustrated. What is wrong with the following code. The actual http call I am doing works; I have run this call myself and it returns the necessary data. It does not work inside the interceptor.

I merely want to get the current implementation working before I add whitelist or blacklist and other customizable data for this interceptor. This is not a question about hmac however but with promises.

The error in this interceptor is with the entire promise line starting at $http(...). When i remove this block and use it as is (minus promise execution) it works fine. As soon as i uncomment the line it gets stuck in a loop and crashes chrome. Everywhere I have read says this is how it is done, but this clearly does not work.

function requestInterceptor(config){
  var $http = $injector.get('$http');
  var deferred = $q.defer();

  $http.get(hmacApiEndpoint, {cache: true}).then(function(data){
    console.log('HMAC - Success', data)
    deferred.resolve(config)
  }, function(config){
    console.log('HMAC - Error', config)
    deferred.resolve(config)
  })

  return deferred.promise;
}

return {
  request: requestInterceptor
};

Does this have something to do with the fact that angulars $http promise is a different implementation than that of '$q'?

share|improve this question
1  
will that $http call from request requestInterceptor will call requestInterceptor again? I doubt that it will call it recursively – Pankaj Parkar May 4 at 19:07
1  
@pankajparkar, I'm almost certain it will... so, to avoid an infinite loop, you should only apply the interceptor to urls other than hmacApiEndpoint. And $http returns the same promise + and additional .success/.error - so, it is the same or compatible – New Dev May 4 at 19:27

1 Answer 1

up vote 5 down vote accepted

It doesn't look like you are actually amending the config with the newly obtainted HMAC.

Also, you'd need to protect against your requestInterceptor intercepting the call to obtain the HMAC, thus resulting in an infinite loop.

And lastly, you don't need deferred here - just return the promise produced by $http (or $http.then()):

function requestInterceptor(config){
  var $http = $injector.get('$http');

  // just return, if this is a call to get HMAC
  if (config.url === hmacApiEndpoint) return config;

  return $http.get(hmacApiEndpoint, {cache: true})
    .then(function(response){
      console.log('HMAC - Success', response.data)

      // not sure where the HMAC needs to go
      config.headers.Authorization = response.data;
      return config;
    })
    .catch(function(){
       return $q.reject("failed to obtain HMAC");
    });
}

return {
  request: requestInterceptor
};
share|improve this answer
1  
good solution, but could you explain me how will not call the interceptor for $http.get you are making for HMAC – Pankaj Parkar May 4 at 19:36
1  
@pankajparkar, It will get called, but it will skip the inner $http call to (again) get the HMAC – New Dev May 4 at 19:40
1  
but everytime that will make an ajax..thats looks like overload.. – Pankaj Parkar May 4 at 20:06
2  
@pankajparkar, how so? The {cache: true} setting would make it retrieve the previous result without an Ajax request. maybe I'm missing something? – New Dev May 4 at 20:14
2  
then that make sense..cool solution..as you gave everytime..you are great..:) +1 from me – Pankaj Parkar May 4 at 20:19

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.