The Charts framework is one among my favorite options for the brand new model of SwiftUI in iOS 16. Previous to iOS 16, you could construct your individual charts or depend on third social gathering library to render charts for you. With the discharge of this new framework, Apple has made it very straightforward for builders to create animated and interactive charts.
I’ve briefly mentioned the utilization of the Charts API in this put up. For this tutorial, let’s see learn how to use the APIs to create a line chart.
The Climate Knowledge
To reveal the SwiftUI Charts API, we’ll create a line chart that shows the common temperature of Hong Kong, Taipei, and London from 2021-Jul to 2022-Jun.
To retailer the climate knowledge, I created a WeatherData struct like under:
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struct WeatherData: Identifiable { let id = UUID() let date: Date let temperature: Double
init(12 months: Int, month: Int, day: Int, temperature: Double) { self.date = Calendar.present.date(from: .init(12 months: 12 months, month: month, day: day)) ?? Date() self.temperature = temperature } } |
The Chart initializer takes in an inventory of Identifiable objects. Because of this we make the WeatherData conform the Identifiable protocol.
For every metropolis, we create an array to retailer the climate knowledge. Right here is an instance for London:
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let londonWeatherData = [ WeatherData(year: 2021, month: 7, day: 1, temperature: 19.0), WeatherData(year: 2021, month: 8, day: 1, temperature: 17.0), WeatherData(year: 2021, month: 9, day: 1, temperature: 17.0), WeatherData(year: 2021, month: 10, day: 1, temperature: 13.0), WeatherData(year: 2021, month: 11, day: 1, temperature: 8.0), WeatherData(year: 2021, month: 12, day: 1, temperature: 8.0), WeatherData(year: 2022, month: 1, day: 1, temperature: 5.0), WeatherData(year: 2022, month: 2, day: 1, temperature: 8.0), WeatherData(year: 2022, month: 3, day: 1, temperature: 9.0), WeatherData(year: 2022, month: 4, day: 1, temperature: 11.0), WeatherData(year: 2022, month: 5, day: 1, temperature: 15.0), WeatherData(year: 2022, month: 6, day: 1, temperature: 18.0) ] |
To retailer the climate knowledge of the cities, we even have an array for that:
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let chartData = [ (city: “Hong Kong”, data: hkWeatherData), (city: “London”, data: londonWeatherData), (city: “Taipei”, data: taipeiWeatherData) ] |
Making a Easy Line Chart Utilizing Chart and LineMark
To create any varieties of chart utilizing the Charts framework, you must first import the Chartsframework:
Subsequent, you begin with the Chart view. Contained in the Chart view, you present a set of LineMark to create a line chart. Right here is an instance:
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struct SimpleLineChartView: View { var physique: some View { VStack { Chart { ForEach(hkWeatherData) { merchandise in LineMark( x: .worth(“Month”, merchandise.date), y: .worth(“Temp”, merchandise.temperature) ) } } .body(peak: 300) } } } |
What the code above does is to plot a line chart for displaying the common temperature of Hong Kong. The ForEach assertion loops via all objects saved in hkWeatherData. For every merchandise, we create a LineMark object that the x axis is ready to the date and the y axis is ready to the common temperature.
Optionally, you possibly can resize the chart utilizing the body modifier. Should you preview the code in Xcode preview, you need to see the next line chart:
Customizing Chart Axes
You’ll be able to customise each x and y axes by utilizing the chartXAxis and chartYAxis modifiers respectively. Let’s say, if we wish to show the month labels utilizing the digit format, we will connect the chartXAxis modifier to the Chart view like this:
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.chartXAxis { AxisMarks(values: .stride(by: .month)) { worth in AxisGridLine() AxisValueLabel(format: .dateTime.month(.defaultDigits)) } } |
Inside chartXAxis , we create a visible mark referred to as AxisMarks for the values of month. For every worth, we show a worth label by utilizing a particular format. This line of code tells SwiftUI chart to make use of the digit format:
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.dateTime.month(.defaultDigits) |
On high of that, we added some grid strains by utilizing AxisGridLine.
For the y-axis, as an alternative of show the axis on the trailing (or proper) aspect, we wish to swap it to the main (or left) aspect. To do this, connect the chartYAxis modifier like this:
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.chartYAxis { AxisMarks(place: .main) } |
Should you’ve made the change, Xcode preview ought to replace the chart like under. The y-axis is moved to the left aspect and the format of month is modified. Plus, you need to see some grid strains.
Customizing the Background Coloration of the Plot Space
The chartPlotStyle modifier means that you can change the background colour of the plot space. Connect the modifier to the Chart view like this:
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.chartPlotStyle { plotArea in plotArea .background(.blue.opacity(0.1)) } |
We are able to then change the plot space utilizing the background modifier. For example, we modify the plot space to mild blue.
Making a Multi-line Chart
Now the chart shows a single supply of information (i.e. the climate knowledge of Hong Kong), so how can we show the climate knowledge of London and Taipei in the identical line chart?
You’ll be able to rewrite the code of Chart view like this:
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Chart { ForEach(chartData, id: .metropolis) { sequence in ForEach(sequence.knowledge) { merchandise in LineMark( x: .worth(“Month”, merchandise.date), y: .worth(“Temp”, merchandise.temperature) ) } .foregroundStyle(by: .worth(“Metropolis”, sequence.metropolis)) } } |
We now have one other ForEach to loop via all of the cities of the chart knowledge. Right here, the foregroundStyle modifier is used to use a unique colour for every line. You don’t need to specify the colour. SwiftUI will mechanically choose the colour for you.
Proper now, all of the cities share the identical image. If you wish to use a definite image, place the next line of code after foregroundStyle:
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.image(by: .worth(“Metropolis”, sequence.metropolis)) |
Now every metropolis has its personal image within the line chart.
Customizing the Interpolation Technique
You’ll be able to alter the interpolation technique of the road chart by attaching the interpolationMethod modifier to LineMark. Right here is an instance:
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.interpolationMethod(.stepStart) |
Should you change the interpolation technique to .stepStart, the road chart now seems to be like this:
Aside from .stepStart, you possibly can check out the next choices:
- cardinal
- catmullRom
- linear
- monotone
- stepCenter
- stepEnd
Abstract
The Charts framework is a superb addition to SwiftUI. Even if you happen to simply start studying SwiftUI, you possibly can create pleasant charts with a number of strains of code. Whereas this tutorial focuses on line charts, the Charts API makes it very straightforward for builders to transform the chart to different varieties resembling bar chart. You’ll be able to take a look at the Swift Charts documentation for additional studying.
Word: We’re updating our Mastering SwiftUI e-book for iOS 16. If you wish to begin studying SwiftUI, take a look at the e-book right here. You’ll obtain a free replace later this 12 months.
