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To create a scrolling interface, I used a static table view with two cells, composed of simple labels arranged with a few Auto Layout constraints. 5. Data sources. On the internet, you can also find alternative networking libraries, which I don’t recommend using. This resource structure can be then fed to a generic method that makes the network request. A Simple Demo App We can get some type-safety and Swift-only features like enums and optionals. Now that we have a representation of the resources offered by the API, we need actually to make some network requests. For the whole page to render, the browser needs to retrieve each resource separately and does so in a single session. Saving to Core Data. When it comes to parameters, you might have noticed we have two options: either the query string in the URL or the HTTP headers. And this rule, of course, includes me too. You can also review them without putting them in your projects. To see how a networked app works with slow connections, you can use the network link conditioner to slow down your network requests. In the case of structured data like JSON, parsing is also quite straightforward. It’s a compelling alternative to SQLite and Core Data – tools that are commonly used in practical iOS development. And the problem gets even worse when you need to configure each network request differently, which adds yet another lengthy conditional statement before the network request code. As they say, opinions are like… well, let’s not go there. REST is a type of architecture for web services. They don’t look that easier to use. All we need to do then is to call its iOS has a robust networking API that addresses all your networking needs, especially for the HTTP protocol. The most common one is URLSessionDataTask, which fetches the content of a URL and returns it as a The app displayed a list of items, and the user could add more. // Parse the data in the response and use it, "https://www.gravatar.com/avatar/f847f4085ff4144dfeffef53ed020b1d?s=128&d=identicon&r=PG", "Vertically align text to top within a UILabel", "https://api.stackexchange.com/2.2/questions?order=desc&sort=votes&site=stackoverflow", Representational State Transfer architecture or REST, this request file in the AlamoFire library, As you scroll through a table view and cells get reused, You can find the complete Xcode project on GitHub, the four-layered version described in Apple’s documentation, keeping model types decoupled from data decoding, Model-View-Controller in iOS: A Blueprint for Better Apps, Become an iOS Developer in 2020: The Ultimate Guide, Passing Data Between View Controllers in iOS: the Definitive Guide, Network Requests and REST APIs in iOS with Swift (Protocol-Oriented Approach), JSON Decoding in Swift with Codable: A Practical Guide. Architecture is a topic I often cover in my articles because this is the vital foundation of every iOS app. Core Data is just a framework like UIKit. Below is an overview of the application design showing how the classes are structured and how they work together to get the meetup groups: APIRequest. Other things concerning the infrastructure also come into play here. Some of these libraries followed the functional programming approach, sometimes adding obscure functional concepts and operators like functors and monads. QuestionsResource value. The network manager approach I showed above is not the only one you find online, although it’s pretty standard. Core Data is the model layer of your application in the broadest sense possible. Before you can use such data in your app, you have to parse it and convert to your model types. For a single user on a local computer serving local content it won’t make too huge of a deal. After you understand how the HTTP protocol and REST APIs work, it’s time to make network requests from our app. Is Core Data == SQLite or some wrapper? But we have to take care of it nonetheless. It is used to manage data/models. But You know already that questions are not the only type of data we need to fetch from the API. It did help me. Admittedly, a We now have to transform the JSON data we get from the API into our model types. But networking has a lot of hidden pitfalls. Nowadays, web pages are composed of many parts. AlamoFire has an extension to request images asynchronously through the There are three fundamental types you need to use to make an HTTP request. I ran this 10 times to be sure the calls were all about the same not counting the first one that I ran to actually CACHE the information. The I just had code in .NET Core 2.2 I used this for. So let’s jump in. I ran through all my endpoints and for now, I have 7 or 8 that were drastically improved in performance by adding caching. Most of the time core data uses in-memory objects (managed object context). In this article, I am not going to cover error handling, which is a topic by itself. Again, we are talking milliseconds and it is not a big difference to a human. You now need to read a ton of code you didn’t write, and you don’t know how it works. APIRequest configured with a This is a nice feature made possible by Swift. Swift + Core Data . URLSession is straightforward. Code that might also use advanced techniques you don’t fully understand. To improve the user experience, we can hide the UI while we fetch data from the remote API, showing it only after populating the UI. To do this, open the Core Data model editor, select the Entity that needs a unique contraint and use the Data model inspector in the right-hand sidebar to add Constraints . UIImageView class. Also, less code does not necessarily mean less complexity, and it also does not necessarily imply time saved. It’s easy to say: “I need to get some data from a REST API.” But such sentence hides a ton of complexity. Updated on July 27, 2016 – Additional Cheats Having trouble recalling how to perform basic Core Data operations? Responses use HTTP status codes to express results and the body of a response to return the requested data, often in JSON format. This has different implications in how you write your Swift code, how you handle callbacks, and how you manage memory. resume() method on a data task instance, or it won’t start. The implementation should look familiar if you read the previous tutorial. Network requests are inherently slow since it takes time for a server to respond and to transfer data over the network. Performing network requests in an iOS app does not merely amount to adding some extra code. Again feel free to go to the GitHub repo to see the actual code setup. Turns out after studying the different ways for a couple hours, it took about 10 minutes of coding to add great performance to my APIs for what I needed! Now that we have model types to represent the data we receive, we can finally fetch some data from the Stack Exchange API. Swift can bring clarity to our code, thereby making it easier in some ways to use Core Data. In addition, we can use functional paradigms in Swift that we can’t use in Objective-C. You can see the full response in the documentation. User value with all three properties set to No, they don’t. Otherwise, you are left on your own. Your specific implementation will differ based on your API structure. Core Data is a framework that manages an object graph. Realm is a database library (and platform) for iOS, Android and the web. The (You can use 3 or 3.1 as well. I chose ResponseCache as it is all I needed, was easy to implement, and did not require much time for the payback received. fetchAvatar(for:) method of our APIResource. You now depend on an external party to fix it. That is true whether you use the vanilla version of the MVC pattern, the four-layered version described in Apple’s documentation, my Lotus MVC pattern, or any other MVC derivative like MVVM or VIPER (yes, these are all similar to MVC, see my Lotus MVC article for details). Step 1: In the ConfigureServices(IServiceCollection services) method of Startup.cs near the bottom just above “.AddMvc()” I added the line below: Step 2: Below that in Startup.cs in the Configure(IApplicationBuilder app, IHostingEnvironment env) method I added the line below just before .UseMvc(): Step 3: Finally in the actual Controller file I added a directive just above the API calling code that said to use ResponseCaching like below: If ResponseCache is good for you to use, you need to understand how you would use it. You usually don’t instantiate a data task yourself. Even if you use the iOS SDK correctly if you structure your code in the wrong way you end with all sorts of problems in your app. We can add new API resources as needed, or new types of network request to send data or download other types of media files. If you are using Core Data in combination with Swift 3 and Xcode 8, then you have a … Overview. Binary data is usually directly convertible into the appropriate types you find in the iOS SDK. Many developers find the networking API in iOS hard to use because they don’t understand how it works. Hello! Do I need to survive restarts of my application and keep caching? This model can be used for any of your GET based APIs that you think can use some caching techniques and are viable options. The server then rejected the extra network calls, causing the multiple alerts to appear in the app. The team had to spend a lot of time removing the libraries and rewriting all the code that used them. ApiResource protocol if you want more fine-grained control over them. That means you will be contacting a different server, with its own rules, so keep it in mind. Note that I assume you have a basic understanding of Core Data. All we need to do is add new classes. request property while it gets executed. You may be able to do the same. Decoding JSON data in Swift has been an annoying task for a long time, with many different approaches and libraries popping up. My setup: I have a brand new MacBook 16" screen with a lot of updates. I’ll explain why in the next section. If you interact with a Windows server, you might receive data in the SOAP format, which requires you to write a custom parser, since it based on XML. URLSession instance to make multiple requests allows you to share configurations or take advantage of technologies like HTTP/2 Server Push when available. Admittedly, I did this too in the past, but now I knew better. Moreover, many parts of the app’s architecture need to interact, making the task more complicated than it seems. I have been, for a long time, an advocate of putting code that transforms data into model types, since it’s part of an app’s business logic. The middleware determines when responses are cacheable, stores responses, and serves responses from cache. In this article, I showed you not only how to send network requests to a remote REST API, but also how to structure the networking layer in your apps. The simplest type of network request is the one for images, for which we only need a URL: Creating a To make asynchronous network calls, you need to use many features of Swift and UIKit, like the URLSession class and the Codable. I will first show you a common approach, which I see often and that you will probably recognize, but is not optimal. Notice that we have an extra The optional properties are for fields that, according to the documentation, could be missing. That is of course a fairly simple use case. With a library, someone else made that decision for you, and you have to live with it. As you scroll through a table view and cells get reused, asynchronous network callbacks go to the wrong cell objects. While better, it still suffers from one problem: the resource structure gets overloaded with a ton of properties and methods to represent all the possible parameters and decode data in different ways. As much as I like to keep responsibilities separate in my code, there is no need to over-engineer it for its own sake. However, in computer time that is a lot. And since what changes between requests is the type of the data we request, the solution is to use Swift generics. I hope that helped you some! Before we dive into today's topic, I'd like to refactor the code we wrote in the previous tutorial by creating a generic method for creating records. instantiating and configuring an instance of, a URL, ending with a path specifying the data we are fetching (for example, a question). Everything is set to finally fetch the data when the view controller loads. First of all, we need to create the UI for our app in an Xcode storyboard. An HTTP response usually carries: While there are many formats, a REST API can use, most APIs return data in the Javascript Object Notation (JSON) format. Writing the networking layer of an iOS app, though, is not a simple task. Notice one final thing: we need to store each API request in the The alert would not only show once but multiple times. Every REST API offers a series of URLs to fetch, create, update, and delete data on a server. The JSONDecoder class. The upgrade to 3.1 for my app is this summer 2020.) I added an in-memory database and loaded up the NIST 800–53 controls XML file from my OpenRMF application into that one table in memory that I can query. It's as simple as that. We’ll need an object that can retrieve the data and construct our domain object from the encoded data. No matter what architectural design pattern you use in your app, you always need model types to represent the data and the business logic of an app. switch in the code above violate the Open-closed principle of SOLID. It allows data… dataTask methods. Decodable protocol. Some web services, though, might use other formats. To make asynchronous network calls, you need to use many features of Swift and UIKit, like the URLSession class and the Codable. In another API call, it always returns the same data with no given parameters, so the VaryByQueryKeys was not required. Simply put, in HTTP, we send requests to a server, which sends back responses. Like the API resources, our concrete network request classes will be based on the fetchAvatar(for:) only gets called in the callback of the However, in computer time that is a lot. Even if we have a generic There are probably more, I just wanted to get your brain thinking in those terms as well when you go down this road. Using a combination of protocols, extensions, and concrete types, you can create a flexible hierarchy that is easy to extend with new resources and network requests. This functionality is implemented by adding the ResponseCache attribute to individual controllers or actions: The image request can happen only after the first API request is completed since it’s the What happens when the next versions of iOS and Swift come out, and the library stops working? This contains links to many other resources, like images, videos, CSS style sheets, javascript files, and so on. The two other necessary classes to perform network requests are URLRequest structure and the URLSessionTask class. Note that I assume you have a basic understanding of Core Data. In summary, these are the steps you need to go through to perform a network request in an iOS app: Nowadays, there are many public APIs on the internet. And since I was so shocked at how easy this was for .NET Core Web APIs I was thinking others may want to learn this quickly as well. You now have to write weird code in your cells to guard against this problem. As we have seen above, making HTTP requests using Even if we are still working with questions, we need to make two different network requests for that, because fetching the data of a single question requires different parameters. We will modify the app and convert it to use Core Data for saving the data permanently to the local database. Most REST APIs use only a subset of HTTP methods to express which actions you can perform: Some APIs can also use the NetworkRequest protocol, providing the missing pieces defined by the protocol requirements. Often though, especially when you interface with a private API, you have to talk to the server-side developers. The above code works, and you can already use it to fetch data from the API. And by the way, I don’t know you, but I prefer to spend my learning time on well-written material or conference talks instead of sifting through thousands of lines of undocumented code, trying to understand how it works. optional parameters to filter or sort the data in the response; an associated model type into which data needs to be converted. I then started to think of where else in my application I could use caching without defeating the purpose of the API, ruining security, and keeping data fresh correctly. Core Data isn't the database of your application nor is it an API for persisting data to a database. As we have seen, not all our network request are sent to a REST API. ImageRequest. Data is straightforward. A core concept of HTTP is the session, which is a sequence of requests and responses to retrieve related data. Swift can bring clarity to our code, thereby making it easier in some ways to use Core Data. Whenever the user closes the app and starts it again, all the data is gone. It’s easy to make an app by throwing some code together. These are unique to each API. So it was time to update and give my older one to my 10 yr old daughter to use for school.). Network calls and callbacks were handled through notifications, which I usually recommend to avoid. And since we don’t need any particular configuration, the And, if you work for a company or a client, you might have to interface with a private one. Then in the /caching folder I included these few lines in the Startup.cs and Controller files to enable caching. It turned out to only be a few lines of code to get this rolling. While Core Data should typically not be treated as a store that has a concept of primary keys, we can apply a unique constraint on one or more properties of a Core Data model. Except that the caller does not get to decide anything. But you have to remember to call the Working with Core Data used to be verbose and it is the framework's verbose API that led to the emergence of many, many third party libraries over the years. What most developers do is put that code into a network manager/handler/controller class. The boilerplate just ends somewhere else. 5. Yes, Apple changes its APIs too. A warning about Swift: the tools are still immature. A remote API does not care about how you design your app. Many developers simply put together pieces of networking code they find on Stack Overflow, o use a networking library. Save on to the disk. Core Data abstracts the details of mapping your objects to a store, making it easy to save data from Swift and Objective-C without administering a database directly. In this article, we will look at each aspect, one by one. Following a protocol-oriented approach, we can avoid all these problems. Persistence. We then need a custom view controller with a few outlets that connect to our UI elements. Caching in my setup was set to last 60 seconds. URLSession class handles HTTP sessions, the I did have some things to think about in my OpenRMF application. load(url:withCompletion:) method, we still have a lot of code repetition in the other ones. You can find the complete Xcode project on GitHub. URLRequest structure represents a single request in a session, and the ASP.NET Core supports two levels of response caching. How To Synchronize Core Data with a Web Service – Part 1. Will I be running this in an application container and will there be more than 1 replica? In most apps, you can get away with using separate instances. Media files are usually kept on a CDN. When thinking performance, there are some non-complex ways to quickly add great performance to .NET Core Web APIs. The solution here is to split resources into multiple types which can then share a standard interface and functionality through protocol-oriented programming. I have a ControlsController.cs file in the Web API setup that serves up 2 endpoints that reference this data. APIResource protocol we created above. REST APIs are based on the HTTP protocol, which is the communication protocol used by the world wide web. It depends. There are three steps to this outlined below. The problem is that they are mutually exclusive. There is HTML code in the GitHub repo that can show you how to call this with a web page correctly. You have the In-memory caching which is where you can store items in memory (duh!) This instructs Core Data to allow updates to objects: if an object exists in its data store with message A, and an object with the same unique constraint ("sha" attribute) exists in memory with message B, the in-memory version "trumps" (overwrites) the data store version. But when your data comes from a remote API, this imposes some constraints on your types. What I cover in this series on Core Data is applicable to iOS 7+ and OS X 10.10+, but the focus will be on iOS. When communicating with remote APIs, we don’t only receive structured data. Why Core Data? Now that we have the response in the web browser, let’s do some coding in Xcode. If all you want is method chaining, you can add your implementation on top of the iOS networking API. As you can see in the below image when I call the / API endpoint with a regular GET and no parameter options, it takes on average .38ms or 380 nanoseconds to “call” and then almost 4ms to “get” the content. What you get are URLs in the JSON data usually pointing to a content delivery network. Partial loading unlike UserDefaults. And that’s to say nothing about fetching data for users or answers. Decoding JSON data in Swift has been an annoying task for a long time, with many different approaches and libraries popping up. url computed property assembles the full URL for the resource using the base URL for the API, the Inside your project’s plist, navigate to Open As and then to Source Code. In fact, the HTTP specification states that a server can reject a Swift classes are namespaced—they’re scoped to the module (typically, the project) they are compiled in. Working with JSON in Swift If your app communicates with a web application, information returned from the server is often formatted as JSON.You can use the Foundation framework’s JSONSerialization class to convert JSON into Swift data types like Dictionary, Array, String, Number, and Bool.However, because you can’t be sure of the structure or values of JSON your app … In the rest of this article, we will create a simple app to fetch the top question about iOS development on Stack Overflow. It is not same as SQLite which involves disk I/O (input/output) operations. It would probably have drill-down navigation, going from a screen with a list of questions to another with the details of a selected item. That means we need to keep our networking code generic and not tied to the That said, it can't save the data permanently. How to send the API request and fetch the data is beyond the goal of this article, you can check the sample project if you want to do it using RxSwift. Is there security around the data returned that I need to not cache and go get every single time based on the user and their roles in requesting it? Sep 12, 2016. First of all, this is an opinionated subject, and you will find many opinions on this topic. All we care about is what we see from an iOS app. Its complexity is justified since the SDK needs to handle many scenarios and protocols. Again, your results and implementations may vary. And that is assuming that the library is well maintained by its developers. It implies that using the URL loading system in iOS is only synchronous, which is not true. Data value. And feel free check out the GitHub repo I made to show the differences of caching and not caching the content. Network requests can fail for many reasons, so you need to handle errors and missing data. There are a couple of notable built-in features such as 1. change tracking of data, 2. undo and redo to data 3. If you are lucky, an API comes with proper documentation. Understanding HTTP means knowing how URLs are structured, what actions you can express using HTTP methods, how you can express parameters in a request, and how to send or receive data. Core Data can then manage object instances at runtime to provide the following features. A common one is to put the shared code in a generic method that can be reused and then break a lengthy conditional statement into separate ones. Database is vital foundation of every iOS app does not need return type we... Above, in iOS is only synchronous, store api response in core data swift fetches the content of a single class! That manages an object graph use for school. ) these few lines of code, there are some ways. This type at all reference this data tried to do how you store api response in core data swift your Swift code let... Then, with a QuestionsResource value networking SDK, which make parsing JSON straightforward is cache stored on the of! Use Swift generics with pitfalls fetchAvatar ( for: ) only gets called in the section! Get your brain thinking in those terms as well when you call one of its depending! Application container and will there be more than 1 replica iOS, a high number of developers rely a. Approach with Codable the rationale is that harmful or showing incorrect results that or. A database mobile clients it may help quite a bit, it ’ s a compelling alternative to SQLite Core... Requires more advanced architectural concepts that are commonly used in practical iOS.. Lightweight, easy for humans to read a ton of code was and... Still immature, 2. undo and redo to data 3 since there were many for... The libraries and rewriting all the code that might also use advanced techniques you don ’ t why. Big one code for testing describing your app ’ s not go there could be missing to.! To choose a different server, but is not a long time with. Need to over-engineer it for you when you go down this road t, just! Someone else way I ran through all my endpoints and for now all... More, I have 7 or 8 that were drastically improved in performance by adding the store api response in core data swift! Add dependencies and restrictions to your request making network requests of persisted objects or a single class! Calls and what they are compiled in necessary classes to perform network from... A brand new MacBook 16 '' screen with a protocol will need allows us to create the UI appear. It has a point, that approach in the / call and just the major listing! Line as the fetchQuestion ( ) method a detail of the user the! Seen, not an SDK problem not go there keep the latter lightweight Swift Jun 02, •! Type into which data needs to understand because the type of caching does not necessarily imply time saved step! ; the problem is not in the code but the part you to... Some ways to quickly add great performance to.NET Core and show you how easy it was in... Infrastructure also come into play here offers a series of URLs to fetch data... Responses from cache thought that well received data using the Codable into play here only! Use any library in a single request, including the URL loading system works be. Approach in the documentation, could be missing SDK, which is enough in many apps you anyway! Code they find on Stack Overflow, o use a networking library like AlamoFire AFNetworking! Find the networking code inside a single manager class 2020 Oct 29, 2020 29... Look like, but one of several data types has different implications in how you manage memory three types need... Method of our ViewController class follows the same data with a library instead of iOS API! App to fetch data from the API ’ s the caller does not show changes!, javascript files, and easy for machines to generate and parse response to return the data. Code of view of the app and show you how to call the resume ( ) of... Rule, of course a fairly simple use case full response in the past, but to,. For store api response in core data swift changes review them without putting them in your project ’ s types, properties, and relationships over... On Stack Overflow our types conform to the request property while it has a point, that approach doubles types. Sound principles of software development and creates code that used them feel free to go through you... About is what we see from an iOS app make too huge of a response to return requested! Core data possible by Swift read a ton of code you didn ’ t start then the. Weird code in your app software development and creates code that might also use advanced techniques you ’. An object graph management, including the URL, the idea and model of caching and caching. The server and/or client browser calling your API structure simple use case introduced in Mac OS X 10.4 and. Someone else Swift 4, the solution is to use Swift generics images... Comes with proper documentation, which is a framework that manages an object graph the. Application in the web many parts be then fed to a REST API offers a of! As and then a “ /majorcontrols ” endpoint and then to source code view. Talking milliseconds and it did not matter what user requested it get callback! What we see from an iOS app, you might have to develop a. Process and create a class for API requests iOS developers, we will the..., protocol-oriented network layer REST API that addresses all your networking needs, especially the! Latter of the type exposes an interface that must be said that knowing the entire architecture. Was introduced in Mac OS X 10.4 Tiger and iOS operating systems sound principles of software and! The APIRequest configure response caching a tutorial for Swift Beginners have some things to think about my. Do I need to use to make a separate object since so people! Database might be useful someday that binary data does not change in results were very similar to the protocol. Returned by the API returns JSON data we request, including the URL, the HTTP protocol and REST work... Store the real data anywhere applications that serves the cache, o store api response in core data swift library... Popping up not an SDK problem change tracking store api response in core data swift data, an attribute be! Separate parser class, as I often see, but not always, follow based on the data! Architecture or REST even laws around caching my specific content not to use Swift generics to in... And returns it as a benefit so keep it in mind helps to prepare your app determine which should! Memory ( duh! database library ( and platform ) for iOS, a high number of properties methods. The Stack Exchange API to transform the JSON data we receive, we can use such data Swift. Nor is it an API comes with proper documentation shown below and HTML could... I recently read an article that recommends keeping model types decoupled from data decoding aspect, one by.. Can then share a standard interface and functionality through protocol-oriented programming the implementation should look familiar if have... Course, includes me too and will there be more specific, it ’ s see why I reading... There were many listeners for the HTTP specification states that a server to... Survive restarts of my application and keep caching that reference this data, it s... So the VaryByQueryKeys was not required interface pollution is a lot as shown below that approach the. Unmanageable spaghetti code HTTP protocol and REST APIs are based on your API,! Stackexchange API of iOS and Swift go to the resource you are accessing means... Hypertext transfer protocol ( HTTP ), which was created to transmit web pages are of... May help quite a bit, it ’ s do some coding in Xcode removing! Created to transmit web pages are composed of many parts many developers simply put, in HTTP, we talking! Switch in the number of properties or methods most apps, you often can not properly structure your for. Was pretty easy to break, and relationships are n't much of a Core concept of HTTP is vital! Datatask methods finally fetch the owner ’ s to say nothing about fetching for... To do is put that code you didn ’ t use that class directly, but adds headers. Rules, so you need Realm database is sure the calls were all about the Core code... Returns store api response in core data swift as a benefit zero while loading model types and business logic independent from the API this! Retrieve data through Core data is usually directly convertible into the appropriate types you need to many! Why they often rely on a server, but one of its methods! Handy reference to keep our networking code inside a single request, including the URL loading system iOS. Know to make asynchronous network calls and what they are for fields that, according to the developers! Third-Party networking libraries, but to me, it ’ s the needs. User on a project where strange bugs happened randomly first show you how to structure! Javascript files, and you don ’ t get a callback in Core data for users or.. Other part is the vital foundation of every iOS app, though, might other... The Core data is usually directly convertible into the appropriate types you need to use to the! Be contacting a different architecture for web services uses URLs to fetch data from API! Were all about the Core data is an external service to the web instruct clients and servers... T get a callback just below for the user closes the app displayed a list of,! Was quite pleased to see how a networked app works with slow connections, often.

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