Angular - Is .finally() Called At the End of Every Path in a Chained Promise Decision Tree?
Solution 1
I wrote a Jasmine test to see whether the finally()
block is called on each function execution no matter what the chained promises returned.
describe('myController Test Suite', function(){
var q, scope, deferred, myService;
// Initialize the Pointivo module
beforeEach(function(){
module('myApp');
});
// Mock out fake service
beforeEach(function(){
myService = {
myFirstPromise: function(){
deferred = q.defer();
// TEST ME
deferred.resolve('first promise response');
return deferred.promise;
},
mySecondPromise: function(){
deferred = q.defer();
// TEST ME
deferred.resolve('second promise response');
return deferred.promise;
},
myThirdPromise: function(){
deferred = q.defer();
// TEST ME
deferred.resolve('third promise response');
return deferred.promise;
}
};
spyOn(myService, 'myFirstPromise').and.callThrough();
spyOn(myService, 'mySecondPromise').and.callThrough();
spyOn(myService, 'myThirdPromise').and.callThrough();
});
// Assign controller scope and service references
beforeEach(inject(function($controller, $rootScope, $q){
scope = $rootScope.$new();
q = $q;
$controller('myController', {
$scope: scope,
myService: myService
});
}));
describe('finally test', function(){
it('should always hit the finally statement', function(){
scope.finallyStatementFlag = false;
scope.test();
scope.$apply();
expect(scope.finallyStatementFlag).toBeTruthy();
});
});
});
The above rests on the assumption that the controller looks like:
myApp.controller('myController', function($scope, myService){
$scope.finallyStatementFlag = false;
$scope.test = function(){
myService.myFirstPromise()
.then(function(data){
console.log(data);
return myService.mySecondPromise()
})
.then(function(data){
console.log(data);
return myService.myThirdPromise();
})
.then(function(data){
console.log(data);
})
.finally(function(){
console.log('finally statement');
$scope.finallyStatementFlag = true;
});
}
});
The above will pass even if you change any or all of the deferred.resolve()
to deferred.reject()
inside of the beforeEach()
callback where we define myService
.
Solution 2
Angular 1.x $q
service inspired by Kris Kowal's Q, based on docs:
finally(callback, notifyCallback) – allows you to observe either the fulfillment or rejection of a promise, but to do so without modifying the final value. This is useful to release resources or do some clean-up that needs to be done whether the promise was rejected or resolved. See the full specification for more information.
so yes, no matter myFirstPromise
resolved or rejected, the finally()
block would always be called
UPDATED,
to be noticed, the finally()
block of myFirstPromise
would be called before mySecondPromise
resolved(or rejected), because myFirstPromise
and mySecondPromise
are different promise instance, and mySecondPromise
promise instance created after myFirstPromise
resolved
Lloyd Banks
Updated on June 05, 2022Comments
-
Lloyd Banks about 2 years
I have the following chained sequence of promises:
$scope.promisesInProgress = true myService.myFirstPromise(id) .then(function(data){ $scope.firstResponse = data; return myService.mySecondPromise(id); }) .then(function(data){ $scope.secondResponse = data; }) .finally(function(){ $scope.promisesInProgress = false; });
Is the
finally()
callback function being called at the very end no matter what the success / failure of the previous two promises are?For example, if
myFirstPromise()
returned a 400 response,mySecondPromise()
will never be called - but I assume thefinally()
block would still be thrown? The same should be true ifmySecondPromise()
returns a 400 (and$scope.secondResponse
is never set) and if both promises return 200s.