I'm using the HotTowel SPA template which makes use of Durandal. In my Durandal ViewModels I am using Breeze to get some data from the database.
I have a datacontext class that I put all my breeze queries in and the queries all follow the pattern like the following:
getAthletes: function (queryCompleted) {
var query = breeze.EntityQuery.from("Athletes");
return manager
.executeQuery(query)
.then(queryCompleted)
.fail(queryFailed)
}
Since I'm doing an asynchronous call in the activate method of the view model, I have to return the promise that comes back from these calls in the activate method.
Using a single query works great like this:
function activate() {
datacontext.getAthlete(loadAthlete);
}
However, if I need to perform two queries I run into problems, but only in the release version of my application. I have tried doing this with the following syntax:
function activate() {
datacontext.getAthlete(loadAthlete).then(datacontext.getOtherData(loadOtherData));
}
This will work fine in debug mode, but when I deploy it out to the server and my scripts get bundled, I get an exception which isn't very clear.
t is not a function
I've also tried chaining them together in my datacontext class like below, but I still get the same error.
getAthleteAndEfforts: function (athleteId, athleteQueryCompleted, effortsQueryCompleted) {
var athleteQuery = breeze.EntityQuery.from("Athletes").where("id", "==", athleteId);
var effortsQuery = breeze.EntityQuery.from("BestEfforts").where("athleteId", "==", athleteId);
return manager.executeQuery(athleteQuery).then(athleteQueryCompleted)
.then(manager.executeQuery(effortsQuery).then(effortsQueryCompleted))
.fail(queryFailed);
}
So I'm assuming I just don't understand the Q.defer() enough to use it properly or there is something else going on.
What is the correct syntax to accomplish this?
Ok, thanks to RainerAtSpirit for pointing me in the right direction to find this. I looked at John Papa's jumpstarter examples and he has a datacontext that does this under the primeData function.
So using the syntax he used there I was able to get it to work correctly like this:
getAthleteAndEfforts: function (athleteId, athleteQueryCompleted, effortsQueryCompleted) {
return Q.all([
datacontext.getAthlete(athleteId, athleteQueryCompleted),
datacontext.getAthleteEfforts(athleteId, effortsQueryCompleted)]);
}
I had seen the Q.all in the Q documentation but wasn't sure how to use it, but this example helped. I tested this and it works both in debug and release modes.
Not sure why the first version is working at all, but you'd return a promise when datacontext is making async calls.
function activate() {
return datacontext.getAthlete(loadAthlete);
}
or
function activate() {
return datacontext.getAthlete(loadAthlete).then( return datacontext.getOtherData(loadOtherData));
}
Check #John Papa's jumpstarter for more examples: https://github.com/johnpapa/PluralsightSpaJumpStartFinal/search?q=activate
Related
There is a sort of "trick" that I've seen around more than once, in order to clear the cache for an MVC app by calling a specific url similar to
http://somewebsite.com/Misc/ClearCache
I used it a couple of times, but honestly I didn't understand exactly how it works and I haven't found any documentation or post about it.
Is there anyone that could explain it a bit, possibly with some related documentation?
Many thanks.
I am not sure if you are using some plugin or 3rd party library for that. But it is as simple as :
write a web method to clearcache like:
public void Clearcache()
{
HttpContext.Current.Response.Cache.SetExpires(DateTime.UtcNow.AddDays(-1));
HttpContext.Current.Response.Cache.SetValidUntilExpires(false);
HttpContext.Current.Response.Cache.SetRevalidation(HttpCacheRevalidation.AllCaches);
HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
HttpContext.Current.Response.Cache.SetNoStore();
}
Call method from browser with like controller/actionname :http://somewebsite.com/Controller/ClearCache
If cache is 3rd party you can delete as required in same method
I was wrong in my comment, no Ajax needed.
Here would be your JQuery:
$("#clearCache").click(function () {
if (!$(this).disabled) {
$('<iframe id="cacheCleared" src="../../Misc/ClearCache"></iframe>').appendTo('body').hide();
}
});
Then in your Misc Controller you would have:
public ActionResult ClearCache()
{
foreach (System.Collections.DictionaryEntry entry in HttpContext.Cache)
{
HttpContext.Cache.Remove((entry.Key).ToString());
}
return View();
}
Once you append your iframe, it will attempt to load the content from that source. When it tries to load that source, it will hit your ClearCache in your controller and should clear everything.
EDIT:
Add this before you return View(); if you want to avoid building a view for it.
System.Web.HttpContext.Current.Response.End();
I am trying to migrate from RxJava1 to RxJava2. I am replacing all code parts where I previously had Observable<Void> to Compleatable. However I ran into one problem with order of stream calls. When I previously was dealing with Observables and using maps and flatMaps the code worked 'as expected'. However the andthen() operator seems to work a little bit differently. Here is a sample code to simplify the problem itself.
public Single<String> getString() {
Log.d("Starting flow..")
return getCompletable().andThen(getSingle());
}
public Completable getCompletable() {
Log.d("calling getCompletable");
return Completable.create(e -> {
Log.d("doing actuall completable work");
e.onComplete();
}
);
}
public Single<String> getSingle() {
Log.d("calling getSingle");
if(conditionBasedOnActualCompletableWork) {
return getSingleA();
}else{
return getSingleB();
}
}
What I see in the logs in the end is :
1-> Log.d("Starting flow..")
2-> Log.d("calling getCompletable");
3-> Log.d("calling getSingle");
4-> Log.d("doing actuall completable work");
And as you can probably figure out I would expect line 4 to be called before line 3 (afterwards the name of andthen() operator suggest that the code would be called 'after' Completable finishes it's job). Previously I was creating the Observable<Void> using the Async.toAsync() operator and the method which is now called getSingle was in flatMap stream - it worked like I expected it to, so Log 4 would appear before 3. Now I tried changing the way the Compleatable is created - like using fromAction or fromCallable but it behaves the same. I also couldn't find any other operator to replace andthen(). To underline - the method must be a Completable since it doesn't have any thing meaning full to return - it changes the app preferences and other settings (and is used like that globally mostly working 'as expected') and those changes are needed later in the stream. I also tried to wrap getSingle() method to somehow create a Single and move the if statement inside the create block but I don't know how to use getSingleA/B() methods inside there. And I need to use them as they have their complexity of their own and it doesn't make sense to duplicate the code. Any one have any idea how to modify this in RxJava2 so it behaves the same? There are multiple places where I rely on a Compleatable job to finish before moving forward with the stream (like refreshing session token, updating db, preferences etc. - no problem in RxJava1 using flatMap).
You can use defer:
getCompletable().andThen(Single.defer(() -> getSingle()))
That way, you don't execute the contents of getSingle() immediately but only when the Completablecompletes and andThen switches to the Single.
I have an application which is written entirely using the FRP paradigm and I think I am having performance issues due to the way that I am creating the streams. It is written in Haxe but the problem is not language specific.
For example, I have this function which returns a stream that resolves every time a config file is updated for that specific section like the following:
function getConfigSection(section:String) : Stream<Map<String, String>> {
return configFileUpdated()
.then(filterForSectionChanged(section))
.then(readFile)
.then(parseYaml);
}
In the reactive programming library I am using called promhx each step of the chain should remember its last resolved value but I think every time I call this function I am recreating the stream and reprocessing each step. This is a problem with the way I am using it rather than the library.
Since this function is called everywhere parsing the YAML every time it is needed is killing the performance and is taking up over 50% of the CPU time according to profiling.
As a fix I have done something like the following using a Map stored as an instance variable that caches the streams:
function getConfigSection(section:String) : Stream<Map<String, String>> {
var cachedStream = this._streamCache.get(section);
if (cachedStream != null) {
return cachedStream;
}
var stream = configFileUpdated()
.filter(sectionFilter(section))
.then(readFile)
.then(parseYaml);
this._streamCache.set(section, stream);
return stream;
}
This might be a good solution to the problem but it doesn't feel right to me. I am wondering if anyone can think of a cleaner solution that maybe uses a more functional approach (closures etc.) or even an extension I can add to the stream like a cache function.
Another way I could do it is to create the streams before hand and store them in fields that can be accessed by consumers. I don't like this approach because I don't want to make a field for every config section, I like being able to call a function with a specific section and get a stream back.
I'd love any ideas that could give me a fresh perspective!
Well, I think one answer is to just abstract away the caching like so:
class Test {
static function main() {
var sideeffects = 0;
var cached = memoize(function (x) return x + sideeffects++);
cached(1);
trace(sideeffects);//1
cached(1);
trace(sideeffects);//1
cached(3);
trace(sideeffects);//2
cached(3);
trace(sideeffects);//2
}
#:generic static function memoize<In, Out>(f:In->Out):In->Out {
var m = new Map<In, Out>();
return
function (input:In)
return switch m[input] {
case null: m[input] = f(input);
case output: output;
}
}
}
You may be able to find a more "functional" implementation for memoize down the road. But the important thing is that it is a separate thing now and you can use it at will.
You may choose to memoize(parseYaml) so that toggling two states in the file actually becomes very cheap after both have been parsed once. You can also tweak memoize to manage the cache size according to whatever strategy proves the most valuable.
I was able to follow the instruction on adding data, that part was easy and understandable. But when I tried to follow instructions for editing data, I'm completely lost.
I am following the todo sample, which works quite well, but when I tried to add to my own project using the same principle, nothing works.
in my controller, I have the following:
function listenForPropertyChanged() {
// Listen for property change of ANY entity so we can (optionally) save
var token = dataservice.addPropertyChangeHandler(propertyChanged);
// Arrange to remove the handler when the controller is destroyed
// which won't happen in this app but would in a multi-page app
$scope.$on("$destroy", function () {
dataservice.removePropertyChangeHandler(token);
});
function propertyChanged(changeArgs) {
// propertyChanged triggers save attempt UNLESS the property is the 'Id'
// because THEN the change is actually the post-save Id-fixup
// rather than user data entry so there is actually nothing to save.
if (changeArgs.args.propertyName !== 'Id') { save(); }
}
}
The problem is that any time I change a control on the view, the propertyChanged callback function never gets called.
Here's the code from the service:
function addPropertyChangeHandler(handler) {
// Actually adds any 'entityChanged' event handler
// call handler when an entity property of any entity changes
return manager.entityChanged.subscribe(function (changeArgs) {
var action = changeArgs.entityAction;
if (action === breeze.EntityAction.PropertyChange) {
handler(changeArgs);
}
});
}
If I put a break point on the line:
var action = changeArgs.entityAction;
In my project, it never reaches there; in the todo sample, it does! It completely skips the whole thing and just loads the view afterwards. So none of my callback functions work at all; so really, nothing is subscribed.
Because of this, when I try to save changes, the manager.hasChanges() is always false and nothing happens in the database.
I've been trying for at least 3 days getting this to work, and I'm completely dumbfounded by how complicated this whole issue has been for me.
Note: I'm using JohnPapa's HotTowel template. I tried to follow the Todo editing functionality to a Tee.. and nothing is working the way I'd like it to.
Help would be appreciated.
The whole time I thought the problem was in the javascript client side end of things. Turned out that editing doesn't work when you created projected DTOs.
So in my server side, I created a query:
public IQueryable<PersonDTO> getPerson(){
return (from _person in ContextProvider.Context.Queries
select new PersonDTO
{
Id = _person.Id,
FirstName = _person.FirstName,
LastName = _person.LastName
}).AsQueryable();
}
Which just projected a DTO to send off to the client. This did work with my app in fetching data and populating things. So this is NOT wrong. Using this, I was able to add items and fetch items, but there's no information that allowed the entitymanager to know about the item. When I created an item, the entitymanager has a "createEntity" which allowed me to tell the entitymanager which item to use.. in my case:
manager.createEntity(person, initializeValues);
Maybe if there was a "manager.getEntity" maybe that would help?
Anyways, I changed the above query to get it straight from the source:
public IQueryable<Person> getPeople(){
return ContextProvider.Context.People;
}
Note ContextProvider is:
readonly EFContextProvider<PeopleEntities> ContextProvider =
new EFContextProvider<PeopleEntities>();
So the subscribe method in the javascript checks out the info that's retrieved straight from the contextual object.. interesting. Just wish I didn't spend 4 days on this.
How are you supposed to conditionally display menu items based on roles in the Bootstrap Sample project? I was thinking of doing the following
Implement INavigatonRouteFilter - really just implementing the shouldRemove(Route navigationRoutes) method - by getting the default controller/action for the route and seeing if the user is authorized
Call NavigationRoutes.Filters.Add(myAuthorizationFilter) after configuring the NavigationRoutes in App_Start
There are two problems I see with this approach:
I don't actually know how to do the first step unless I add in a bunch of conditional statements to check for Controller's name explicitly
This seems like it could make NavigationRoutes.Filters very hard to deal with once there are a lot of filters or a desire for more modularity later on
I don't know that I've explained the problem clearly enough, but basically I want to use what is provided in the Bootstrap sample to implement authorization-based navigation menu display if at all possible. Using INavigationRouteFilter just seemed like the most natural way to do so.
For those looking for an answer or at least a quick fix.
Here's what I've come up with after 5 minutes and I most certainly haven't though about any side effects this may have.
routes.MapNavigationRoute<HomeController>("Index", c => c.Index())
.FilterRoute(() => !WebSecurity.IsAuthenticated);
You can either do all your filtering in your call to FilterRoute() or you can add more extension methods to save you some characters.
I'm thinking of .RequireRole("Adiministrators"); that calls WebSecurity.RequireRoles() in turn (or HttpContext.Current.User.IsInRole()) etc.
public static NavigationRouteBuilder FilterRoute(this NavigationRouteBuilder builder, Func<bool> func)
{
var currentRoute = builder._parent;
NavigationRoutes.Filters.Add(new BootstrapAuthorizationFilter(builder, x =>
{
if (x == currentRoute)
return func();
else
return false;
}));
return builder;
}
and BootstrapAuthorizationFilter is just a class implementing INavigationRouteFilter that calls func() in its ShouldRemove() method
public class BootstrapAuthorizationFilter : INavigationRouteFilter
{
private NavigationRouteBuilder builder;
private Func<NamedRoute, bool> func;
public BootstrapAuthorizationFilter(NavigationRouteBuilder builder, Func<NamedRoute, bool> func)
{
this.builder = builder;
this.func = func;
}
public bool ShouldRemove(Route navigationRoutes)
{
if (navigationRoutes is NamedRoute)
return func(navigationRoutes as NamedRoute);
return false;
}
}
Clearly nothing fancy and I'm not sure if I'd use it in production.
But I think is simple enough and works (for the cases I tested).
Having said that, I hope the new routing functionality is going to be released soon :)