I am writing a SwiftUI app that needs to read an external SQLite database. I just need to open the database, query the database, copy values into an array and close the database. Then I need to load the text from one variable in the array to the buttons in a view. I am using the SQLite.swift library but I'm not sure how to do it.
I don't have any code yet but I have loaded the SQLite.swift package and just need to write my DatabaseHelper class and then run it when the View is opened. If anyone can help please reply! :)
Bear in mind that I haven't actually done this, but will have to in the near future. You are going to have to accept the fact that you need to take baby steps and throw out half your work, perhaps multiple times, until you get a satisfactory solution.
I would start by opening your db outside swiftui, probably in the app delegate class. Then stick all your values into the environment object and attach that to your content view
let contentView = ContentView().environmentObject(your_stuff_here)
Down in Swiftui you can extract the details from the environment object and add them to your button.
That should at least get you going.
Related
I am new to Xamarin. I have done a couple of smaller projects (2-3 pages, one table). I have a new project that is a great candidate for a shell app. It will have 20 pages, will consume data from a transactional database (cloud hosted) but also have an offline datastore (SQLite). Right now, I just want to get the local version up and running. The template for Shell App generates an IDataService and a MockDataStore. That is a great place to start - but how do I have more than one table? I am a little confused how I would use that. What I would love to see is a template generated shell app that just adds another table (and corresponding list,detail views along with view models. For example, the simple "todo" sample but add a contact table to assign todo tasks to would be perfect. Thanks in advance for your help.
I hope this helps others new to Xamarin. When starting a new project and choosing anything other than the "blank template", the template generates a model (Item) and a services folder containing an Interface (IDataStore) and a MockDataStore. Being new to XAML in general, I spent a lot of time working on getting the UI to look like what I wanted it, learning about Shell navigation and similar topics. Finally it was time to include the data part of my project. Where I got stuck was trying to make sense of the boilerplate code. My understanding of DependencyService was for platform specific code (e.g. Android, iOS) and NOT data service dependency. Further, the templated code is a typed interface (IDataStore). The solution was fundamental - all that interface does is insure CRUD operations are available in whatever you use in a datastore. For me, simply changing IDataStore to not be typed as an Item, solved everything. It allowed me to keep the database layer abstracted away. In my little project, I completed my "MockDataStore" adding additional CRUD operations until I was ready for my real data operations. NOTE: if you generate the WEB API project from the template, it will make more sense - you can flip between your MockDataStore and actual data store.
I am new to android and java and working on an app that has a few remaining problems that I haven't resolved yet.
I have a main activity that is a viewPager, with each page being a fragment. If the 4 fragments 3 are extended from ListFragments and one from PreferencesFragment.
The ListFragments have CursorAdapters to get data to and from SQLite databases through providers.
I am able to get data into the database, insert, modify and query the data correctly and fill the list views ok.
My preference setting are to choose different ways of viewing the data in the database.
Not knowing how to do this, I have implemented a process where I modify the cursorLoader query to the provider with a number of different choices of the "WHERE" clause. I have worked out the logic for the preferences as they exist now, implemented the code but had some difficulty finding what to try to trigger the refresh of the ListView.
Since the "dataset" hasn't really changed, no trigger can come from there, plus that would just use the same cursor as it currently exists to run the query again and return the same results (or be smart enough to know that it doesn't need to run).
On Stack Overflow I did find a couple of references to a similar implementation that suggested reStarting the cursor loader, which would then on the reStart read the current values in the stored Preferences file, create a now modified WHERE clause that will show the sub-set of data as specified in the preference settings.
In testing the app now, even with the reStart of the cursorLoader, the ListView isn't getting refreshed.
The only time I can get it to work right is restarting the app. If I stop the app and restart it, the new values are used and the ListView presents as the preferences dictate.
In looking through Stack Overflow and the Android site, I did find another set of APIs that might have been a more natural fit for what I am trying to do, namely the Filter APIs.
First question then would be, did I go in the wrong direction on how to control the "filtered" view of the datbase. Is filtering a better approach and a recommended way of
doing what I am trying to do?
Second question would be related to the fragment lifecycle of my ListFragments to achieve this CursorLoader update.
Thanks for any input on the topic.
-Dan
Found my problem here.
Two things, the way I am trying filtering is working and from what I have seen in the
Android development site, a reference there indicated that the filtering capability is
already implemented in the CursorAdapter, CursorLoader classes I am using.
When my preference settings changed, I did a reStart of the cursorLoader, but had restarted the wrong one.
Problem solved. Any input on is there a better way would be appreciated.
Regards, Dan
First - I am having a hard time formulating this question, so please bear with me, and ask for clarification and I'll try to provide as much as I can. I am just starting to learn meteor, so be patient please.
I have several inputs that save immediately as people type on them. (with a slight 300 ms delay to not overload database).
Basically, on "keyup" it goes and saves. All that works fine. However, I'd like to add a visual indicator (say a green checkmark, or a tiny "saved") when the database actually stores what they typed.
Graphically:
[___________________]
[Typed something_____] (saved)
[___________________]
I am not sure how to go about this, but it's something common, that plenty of you have already done. If I didn't care about the database feedback, I'd just use JQuery, target a class beside the input and make the checkmark or word visible after a keyup, or add it to the DOM. Fairly straight forward.The only when I am sure it has been stored in Mongodb part confuses me.
Any help would be gladly appreciated.
Thank you
Addendum with code:
Template.dibs.events({
'keyup input.name': _.throttle(function(event) {
Dibs.update(this._id, {$set: {name: event.target.value}});
$(':focus + .glyphicon-ok').css('opacity',1);
}, 300),
Can you explain where/how you would add the code? (For spinner, or the words).
Coming from JQuery I did something that I know is not the right way. This is in the client portion (I know just demo code, and it's not secure) but I wanted to know the best way leveraging meteor to do it. I already have checkmarks stating it was saved in the page, but they are all hidden, this code just makes them visible on keyup for the field.
I read through the article, and didn't quite see how I'd go about doing the intermediate step (spinner or the like) then the finalized checkmark after code is saved. I've also being going through the new 1.0 tutorial (which is great) but I'm still missing the visual indicators. It's great that meteor updates the UI if it fails in the server to reflect that it didn't save, since I am assuming success, I don't think that tapping into the Meteor.Error makes sense. Should there not be a Meteor.Success or equivalent?
Again, I apologize for the long message, I'm trying to wrap my head around this, because the technology looks very promising
Welcome to Meteor! Meteor was in fact designed (among other things) to handle just this type of situation, via a mechanism called Latency Compensation. You can read more about it at Meteor.methods.
Calling a method on the server requires a round-trip over the network. It would be really frustrating if users had to wait a whole second to see their comment show up due to this delay. That's why Meteor has a feature called method stubs. If you define a method on the client with the same name as a server method, Meteor will run it to attempt to predict the outcome of the server method. When the code on the server actually finishes, the prediction generated on the client will be replaced with the actual outcome of the server method.
You can use Latency Compensation by defining a Meteor method to save the input text to the database, with a client stub that displays a spinner instead of "saved", and "saved" when its callback is called successfully.
Alternatively, you can call the update method on the collection directly, and add a callback on the client, which will be called with (error, numberOfDocsUpdated) after the server method returns.
Read more on when to use Meteor methods and when to use client-side operations.
As Dan has said, the Latency Comp takes care of needing to do this. Another way of doing this is in a template event. You can set a session variable on keyup with the contents of the text field and in the helper, set a flag that will render the checkmark when the session variable and current user input matches.
How do you access a Meteor collection that already exists? It's easy enough when you have created the collection in the session because you have a variable that references it, but you can't access a collection by name.
What happens if for example you want to retrieve documents from an existing collection in a new session where it is not being created for the first time. I have tried to 're-create' it hoping that it would just assign the existing collection to the new variable name (seeing that I can't find it by name), but it just throws an error to tell you that the collection already exists.
I've got some externally generated collections that I'm accessing via meteor. I'm not 100% sure that this will answer your question, but I hope it'll at least help.
One gotcha (doesn't apply to you it sounds like, here for completeness) is that if your collection was not created by Meteor, you'll need to export an environment variable to point Meteor to your DB.
For example, if the following env. variable is exported in the shell:
MONGO_URL=mongodb://localhost:3002/foo
...and then you invoke the meteor application, it'll point to the db "foo" in MongoDb, at which point you simply defined your collections as #Akshat mentions above in his comment:
collection = new Meteor.Collection("fooCollection") // this lives inside the foo DB.
If you're dealing with collections that have already been created by Meteor, by default they'll be inside the meteor db, eg:
MONGO_URL=mongodb://localhost:3002/meteor
...and you should be able to simply hook into them the same way; by simply declaring your collection and using it as you would. No need to create, obviously.
It sounds like you're already doing this but for other newcomers like me: in cases like this it's really handy to use the console in Chrome, Firefox, etc. and do some inserts that way - you'll see where your data lands, or you'll see other good bits of information that will help you home in on the issue - console.log() has saved my bacon a couple of times.
At any rate, it's worth validating exactly where the Meteor app is pointing vs. where you think it's pointing. Your collections should be accessible and should Just Work...
I wish use nsmanagedobject to use a sqlite database into my project..
I downloaded CoreDataBooks sample but there's something that I don't understand right...
for example... where is the link between the tables and xcdatamodel?
i tried to change the sqlitedb with my db and change xcdatamodel but doesn't work
can you help me?
thanks
Hmm, the way it works is this:
Create a data model in the editor in xcode.
Tell xcode to generate classes to represent the data model.
Write your app, adding in the setup code for core data to instantiate a Managed Object Context, etc.
Add the code to create and save data model objects to the managed context.
some time later ...
Modify the model in xcode's editor to represent changes to you app.
Regenerate associated model classes.
From your description it sounds like you are trying to edit the database directly and manage the classes that represent it yourself. I suspect this is possible, but using xcode's tools is easier and everything its taken care of for you.
Does that help?