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Making a Line Chart Utilizing SwiftUI Charts API


The Charts framework is certainly one of my favorite options for the brand new model of SwiftUI in iOS 16. Previous to iOS 16, it is advisable to construct your personal charts or depend on third celebration 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 submit. For this tutorial, let’s see use the APIs to create a line chart.

The Climate Information

To reveal the SwiftUI Charts API, we’ll create a line chart that shows the typical temperature of Hong Kong, Taipei, and London from 2021-Jul to 2022-Jun.

To retailer the climate knowledge, I created a WeatherData struct like beneath:

The Chart initializer takes in an inventory of Identifiable objects. For this reason 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:

To retailer the climate knowledge of the cities, we even have an array for that:

Making a Easy Line Chart Utilizing Chart and LineMark

To create any kinds of chart utilizing the Charts framework, it’s a must to 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:

What the code above does is to plot a line chart for displaying the typical temperature of Hong Kong. The ForEach assertion loops by all gadgets saved in hkWeatherData. For every merchandise, we create a LineMark object that the x axis is about to the date and the y axis is about to the typical temperature.

Optionally, you possibly can resize the chart utilizing the body modifier. Should you preview the code in Xcode preview, it is best to see the next line chart:

swiftui-line-chart-simple

Customizing Chart Axes

You possibly can 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:

Inside chartXAxis , we create a visible mark known 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:

On high of that, we added some grid strains by utilizing AxisGridLine.

For the y-axis, as a substitute of show the axis on the trailing (or proper) aspect, we wish to swap it to the main (or left) aspect. To try this, connect the chartYAxis modifier like this:

Should you’ve made the change, Xcode preview ought to replace the chart like beneath. The y-axis is moved to the left aspect and the format of month is modified. Plus, it is best to see some grid strains.

swiftui-charts-changing-axis

Customizing the Background Colour 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:

We are able to then change the plot space utilizing the background modifier. For example, we alter the plot space to mild blue.

swiftui-line-chart-background

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 possibly can rewrite the code of Chart view like this:

We’ve one other ForEach to loop by all of the cities of the chart knowledge. Right here, the foregroundStyle modifier is used to use a distinct colour for every line. You don’t must specify the colour. SwiftUI will mechanically decide the colour for you.

swiftui-multi-line-chart

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:

Now every metropolis has its personal image within the line chart.

swiftui-line-chart-symbol

Customizing the Interpolation Technique

You possibly can alter the interpolation methodology of the road chart by attaching the interpolationMethod modifier to LineMark. Right here is an instance:

Should you change the interpolation methodology to .stepStart, the road chart now appears to be like like this:

swiftui-chart-interpolation-method

Apart 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 for those who simply start studying SwiftUI, you possibly can create pleasant charts with a couple 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 types comparable to bar chart. You possibly can take a look at the Swift Charts documentation for additional studying.

Word: We’re updating our Mastering SwiftUI guide for iOS 16. If you wish to begin studying SwiftUI, take a look at the guide right here. You’ll obtain a free replace later this 12 months.



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