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What is a Swift Struct

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A struct, or structure, is a custom data type in Swift that allows you to add many properties to it. If you think of a regular string, you can store just one string in the variable, as follows:

var firstName = "Matthew"

What if we wanted to add Matthews height:

var firstName = "Matthew"
var height = 190

This rapidly becomes complicated because we now have two variables to manage and think about. Imagine if we needed to add their last name, and so on, and then have the need to pass this information somewhere else within the program. This is one benefit of using a struct.

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SwiftUI Text View

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The basic template for SwiftUI View begins with a simple Text view:

struct ContentView: View {
    var body: some View {
        Text("Hello World!")
    }
}

When a Text view is returned with no attributes, it is put it in the middle of the view.

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Using Codable to Encode and Decode JSON

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Codable provides a way to convert to and from formats such as JSON. In this tutorial we’ll just focus on converting JSON. The JSON format is popular among web services and provides a standard about how data can be represented. JSON formatted data can be understood by various systems making it possible to easily transfer data from one system to another regardless of operating system or programming language used.

On the iOS side, Codable is one way to convert an object or structure in to the JSON format so that the other end of the network can accept it and understand it as needed.

The Gmail API is one example of a service that provides data in JSON form. When you query the API the results come back as JSON. We don’t particularly care what programming language and operating systems are involved on the other side. All we need to know is that the response provided conforms to the JSON standard and thus, we can use Codable to convert that data in to whatever we need within our code.

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How to Use the SwiftUI List View with Dynamic Cells

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In a recent tutorial we covered how to combine views and briefly touched on dynamic cells within a List. In this tutorial we’ll look more closely at how you can bring in dynamic content in to a List.

Create a new project and make sure you select SwiftUI when the option is presented.

Open up ContentView.swift and just below the import line at the top of the file, add the following struct:

struct Message: Identifiable {
    var id = UUID()
    var from: String
    var date: String
    var subject: String
    var snippet: String
}
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Combining SwiftUI Views

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One of many things that make SwiftUI great is the ability to combine views. The template code when you create a new SwiftUI view contains the following:

struct ContentView: View {
    var body: some View {
        Text("Place Holder")
    }
}

The body variable is expecting some View. In the example above we are returning a Text view which contains a string “Place Holder”. If you preview this in the canvas you will see the words “Place Holder”, without quotes, in the centre of the view.

Swift provides the ability to combine views so that more views can be combined in to one and then returned. In our Stacks tutorial we explain this. In short, you can combine views in to a HStack, VStack, or ZStack and return the stack as one view.

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How to Use the SwiftUI List View with Static Cells

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SwiftUI allows us to make static table views by using a List view. The SwiftUI syntax makes the process extremely simple. Unlike UITableViewControllers that require you to manually specify that you are using static cells, and then have to assign the table view controller a class, you simply just add “List { }” to your code and insert all of the views you want in-between the curly braces.

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SwiftUI HStack, VStack, ZStack Tutorial

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When you create a SwiftUI view, the protocol defines that we need to return “some View”. The word “some” means that we are dealing with an opaque result type. This is a new feature added added in Swift 5.1. An opaque result type means that we must return one, and only one, of the specified type, in this case something that conforms to the “View” protocol.

This highlights a problem. Imagine if our view, ie… the part that the user interacts with on screen, was only able to show one Text field or perhaps one button, then interfaces would be incredibly boring.

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Getting a List of Messages with the Gmail API

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After authenticating with Google using GoogleSignIn, one of the next steps I wanted to tackle in my app was retrieving a list of messages. Here is the reference on this part of the API. What we see is that it requires a userId (which is your email address… or alternatively just the value “me”).

It has some optional query parameters such as indicating if you want to also include trash and spam folders, as well as filtering on labels. You can also pass in a query string in exactly the same format as you would the Google Search Box on email. Such as “from:[email protected]”, or just by keyword or phrase, etc…

On the right of the page there is also a way to test this out. In userId put in your email address and in labelIds, put in the word INBOX in CAPS.

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Implementing GoogleSignIn with Swift

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I am currently in the process of building an email client app for iOS, and after that, the Mac. At the moment I am working on users being able to sign in to their Gmail account so that they can manage emails with within the app.

One of the first steps with working with the Gmail API is to be able to sign in. At the moment I have implemented GoogleSignIn which is one of a few ways that Google allows you to authenticate.

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