AngularJS : chaining http promises $q in a service
i have problems when it comes to $http promises in angularjs. i am doing this in my service: (the getSomething function should chain two promises)
the second function uses a external callback function!
app.service('blubb', function($http, $q) {
var self = this;
this.getSomething = function(uri, data) {
return self.getData(uri).then(function(data2) {
return self.compactData(uri, data2);
});
};
this.getData = function(uri) {
var deferred = $q.defer();
$http.get(uri).success(function(data) {
deferred.resolve(data);
}).error(function() {
deferred.reject();
});
return deferred.promise;
};
this.compactData = function(uri, data) {
var deferred = $q.defer();
/* callback function */
if(!err) {
console.log(compacted);
deferred.resolve(compacted);
} else {
console.log(err);
deferred.reject(err);
}
/* end of function */
return deferred.promise;
};
});
when i use the service in my controller it doesn't output the console.log:
blubb.getSomething(uri, input).then(function(data) {
console.log(data)
});
edit: if i define the callback function by myself in 'compactData' it works, but i am using "jsonld.compact" from https://raw.github.com/digitalbazaar/jsonld.js/master/js/jsonld.js and THIS doesn't work!
jsonld.compact(input, context, function(err, compacted) {
if(!err) {
console.log(compacted);
deferred.resolve(compacted);
} else {
deferred.reject('JSON-LD compacting');
}
});
i am getting the console.log output in jsonld.compact but the resolve doesn't work and i don't know why..
it only works with $rootScope.$apply(deferred.resolve(compacted));
我正在使用像这样的链接承诺：
$http.get('urlToGo')
.then(function(result1) {
console.log(result1.data);
return $http.get('urlToGo');
}).then(function(result2) {
console.log(result2.data);
return $http.get('urlToGo');
}).then(function(result3) {
console.log(result3.data);
});
Chaining promises works here : jsfiddle
In your implementation, if $http.get or compactData goes wrong your console.log(data) will not be call.
You should maybe catch errors :
blubb.getSomething(uri, input).then(function(data) {
console.log(data);
}, function(err) {
console.log("err: " + err);
});
Whenever you use an external (external to AngularJS) callback that runs in a new turn/tick, you have to call $apply() on the appropriate scope after it has been invoked. This lets AngularJS know it has to update. You'll probably want to make sure you're only calling it once -- after all of the promises have been resolved. As an aside, jsonld.js provides a promises/future API, so if you're already using promises, you don't have to do that wrapper code above. Instead you can do:
var promisesApi = jsonld.promises();
var promise = promisesApi.compact(input, context);
// do something with the promise
上一篇: 链接承诺，或一个承诺触发另一个承诺