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This website is called speakerback.com, speakerback.com/forever. Just in case you need it.
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This talk is about Rails, specifically in Birmingham on Rails, and it focuses on a library called Active Storage. This library simplifies the process of uploading and downloading files. As Brian mentioned at the beginning, you should all learn something if possible. If you haven't used Active Storage before, you're going to see how easy it is to use. If you have used Active Storage, I'm going to delve a bit deeper into some advanced features. And even if you're not interested in Active Storage, you might still learn something about iOS development.
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This talk is structured in three parts, like every great talk or movie. I'll take a short break after each part and I was going to see if you wanted to ask questions, but logistically that might be difficult, so please hold your questions until after the talk.
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The first part will cover the basics: how to use Active Storage to upload files through the browser. The second part is the core of this talk, where we go beyond just uploading and downloading files. We'll explore how to analyze these files and extract information from them. Finally, in the last part, I will discuss validation, including how we can create a better user experience by notifying users if they are uploading the wrong file. Let's get started.
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For this talk, I'll use a real Rails application that is actually open source. It's hosted at GitHub: darkrum/cradle/MDMA, which stands for Mobile Deployment Management Agents.
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Swift is built with Xcode to create an iOS app. At the end, we have this package, which is an IPA file. So, when you have this package, it can be distributed so that you can use these apps. It has various features, but I'm focusing on the main two components: first, the page where an iOS developer uploads a package using a file uploader; and second, where they specify which version of the iOS app it is.
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Typically, a developer might go to the second page to see if there is a test version of the app available for download. This is just a basic example to demonstrate how you can upload and download files.
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Let me break down these two pages for you. The first is the 'create' action in the Rails application. I created a model called 'Build,' which has two fields: the file itself, referred to as the package, and the version. When you submit the form, you'll see parameters for both the package and the version.
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Now, if you've used file uploads with other libraries, you'll notice that Active Storage simplifies this process significantly. Let's look at how you can implement Active Storage for your file uploader.
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First, in the view (HTML), you need to add the file uploader to display in the browser. You can add a file field for the package, which allows users to click 'Choose file.' Next, in the controller, you need to whitelist the parameters, ensuring that the package can be submitted. Finally, you add a single line of code to your model to specify that it has one attached package. This is done using the 'has_one_attached' method from Active Storage, enabling the use of file uploads.
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When it comes to downloading the file, you'll want to create a link in your index view. You can use a helper method called 'url_for' in conjunction with the package object to create a download link.
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You may wonder where the uploaded files are stored. This depends on your application's configuration. For instance, if you want to upload files to Amazon S3, you can specify this in your application's production environment configuration. Default options include Microsoft Azure, Google Cloud Storage, and local disk storage for testing purposes.
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This basic structure is straightforward compared to other libraries. However, you might want to add some validations. For example, if a user forgets to attach a file, we should notify them that the package can't be blank. You can accomplish this with a simple validation check.
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If again, you'd like to add more specific validations, such as ensuring that a file is not too large or has the correct content type, you can also follow a similar syntax to validate these criteria. There is an ongoing discussion about adding these validations to the Rails codebase.
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Now, let's transition to the second part of my talk. Uploading and downloading files are relatively straightforward, but can we do more?
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This is precisely what the functionality is intended to achieve: an iOS developer uploads a package, and a QA developer can open the website on an iPhone, click on the package, and directly install the app on the phone. This process eliminates the need to use the App Store for application distribution.
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However, directly sharing an IPA file link might not work as intended. When opened on Safari on the phone, you'll be prompted to choose where to download the file. Instead, we want to create a direct install link, which involves additional processing.
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In detail, you need to open the package and locate an XML file containing essential information about the iOS app, such as its name, version, and minimum iOS version. You then create a new file called a manifest containing this information, upload it, and link it to your primary file.
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Active Storage can facilitate all these processes seamlessly. We're able to analyze the uploaded file and extract the necessary data.
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Consider an example: if you upload a JPEG file using Active Storage, it can automatically extract the image's width and height using an Image Analyzer built into Active Storage. A similar function exists for videos, extracting the resolution and duration.
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To create a custom analyzer for iOS packages, we follow a similar structure. After creating a build, we call our package analysis job. This job analyzes the package file and retrieves its details, which are then stored in the database.
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We can extract information from the package files using the CFBundle APIs, which allow us to open an IPA file and extract various properties. Once we have that data, we can store it in our database for future access.
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As we move forward refining our process, we will ultimately want to generate an XML file containing all the metadata extracted from our package. We create this XML using a temporary file, writing the XML declaration and interpolating the relevant metadata.
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Once the XML file is ready, we can upload it using Active Storage's built-in capabilities. So not only do we attach the main package, but we also attach the manifest. This flexible approach allows us to generate and manage multiple related files effectively.
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After all this processing, we replace the URL of the manifest file using the appropriate format that Apple provides. This step is crucial because it allows the application to be installed correctly on an iPhone without any hassle.
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Now that we have everything in place, it's time to think about user experience once again. During the initial upload process, we need to extract the version number from the package to enhance the submit form.
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The version number is critical for the correct functioning of the app download process. We will validate it before submission, so the user does not encounter any roadblocks during the installation.
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We ensure that we're providing a smooth user experience this way, paving the way for a faster and easier installation process.
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In the section on validations, we also make sure to account for what happens if a user forgets to attach a file. There should not be multiple errors displayed at once, so we'll handle those cases effectively.
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Finally, it is essential to account for any errors during the analysis of the uploaded package. This feedback helps users know if something went wrong with their upload before further processing.
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In conclusion, I've shared a lot about working with Active Storage and the various ways it can enhance your development process. There is much more to explore, including JavaScript components to facilitate file uploads from browsers directly to S3 without the overhead of spending time in Rails.
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There's always something new evolving within Active Storage, so I encourage everyone to keep an eye on the latest updates and enhancements coming in future versions. I hope this talk was insightful and that you learned something valuable today.
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Thank you, and I'm happy to answer any questions you might have.
