SwiftChart

A simple line / area charting library for iOS, written in Swift.

📈 Line and area charts
🌞 Multiple series
🌒 Partially filled series
🏊 Works with signed floats
🖖 Touch events

Installation

CocoaPods

SwiftChart is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "SwiftChart"

Manually

1. Download SwiftChart.zip from the last release and extract its content in your project's folder.
2. From the Xcode project, choose Add Files to ... from the File menu and add the extracted files.

Usage

The library includes:

• the Chart main class, to initialize and configure the chart’s content, e.g. for adding series or setting up the its appearance
• the ChartSeries class, for creating datasets and configure their appearance
• the ChartDelegate protocol, which tells other objects about the chart’s touch events
• the ChartColor struct, containing some predefined colors

Example

let chart = Chart()
let series = ChartSeries([0, 6, 2, 8, 4, 7, 3, 10, 8])
series.color = ChartColors.greenColor()
chart.add(series)

To run the example project, clone the repo, and run pod install from the Example directory first.

To initialize a chart

From the Interface Builder

The chart can be initialized from the Interface Builder. Drag a normal View into a View Controller and assign to it the Chart Custom Class from the Identity Inspector:

Parts of the chart’s appearance can be set from the Attribute Inspector.

By coding

To initialize a chart programmatically, use the Chart(frame: ...) initializer, which requires a frame:

let chart = Chart(frame: CGRect(x: 0, y: 0, width: 200, height: 100))

If you prefer to use Autolayout, set the frame to 0 and add the constraints later:

let chart = Chart(frame: CGRectZero)
// add constraints now

Adding series

Initialize each series before adding them to the chart. To do so, pass an array to initialize a ChartSeries object:

let series = ChartSeries([0, 6.5, 2, 8, 4.1, 7, -3.1, 10, 8])
chart.add(series)

By default, the values on the x-axis are the progressive indexes of the passed array. You can customize those values by passing an array of (x: Float, y: Float) touples to the series’ initializer:

// Create a new series specifying x and y values
let data = [(x: 0, y: 0), (x: 0.5, y: 3.1), (x: 1.2, y: 2), (x: 2.1, y: -4.2), (x: 2.6, y: 1.1)]
let series = ChartSeries(data)
chart.add(series)

Multiple series

Using the chart.add(series: ChartSeries) and chart.add(series: Array<ChartSeries>) methods you can add more series. Those will be indentified with a progressive index in the chart’s series property.

Partially filled series

Use the chart.xLabels property to make the x-axis wider than the actual data. For example,

let chart = Chart(frame: CGRect(x: 0, y: 0, width: 200, height: 100))
let data = [(x: 0.0, y: 0), (x: 3, y: 2.5), (x: 4, y: 2), (x: 5, y: 2.3), (x: 7, y: 3), (x: 8, y: 2.2), (x: 9, y: 2.5)]
let series = ChartSeries(data: data)
series.area = true
chart.xLabels = [0, 3, 6, 9, 12, 15, 18, 21, 24]
chart.xLabelsFormatter = { String(Int(round($1))) + "h" }
chart.add(series)

will render:

Touch events

To make the chart respond to touch events, implement the ChartDelegate protocol in your classes, as a View Controller, and set the chart’s delegate property:

class MyViewController: UIViewController, ChartDelegate {
    override func viewDidLoad() {
        let chart = Chart(frame: CGRect(x: 0, y: 0, width: 100, height: 200))
        chart.delegate = self
    }
    
    // Chart delegate
    func didTouchChart(chart: Chart, indexes: Array<Int?>, x: Float, left: CGFloat) {
        // Do something on touch
    }
    
    func didFinishTouchingChart(chart: Chart) {
        // Do something when finished
    }
}

The didTouchChart method passes an array of indexes, one for each series, with an optional Int referring to the data’s index:

 func didTouchChart(chart: Chart, indexes: Array<Int?>, x: Float, left: CGFloat) {
        for (serieIndex, dataIndex) in enumerate(indexes) {
            if dataIndex != nil {
                // The series at serieIndex has been touched
                let value = chart.valueForSeries(serieIndex, atIndex: dataIndex)
            }
        }
    }

You can use chart.valueForSeries() to access the value for the touched position.

The x: Float argument refers to the value on the x-axis: it is inferred from the horizontal position of the touch event, and may be not part of the series values.

The left: CGFloat is the x position on the chart’s view, starting from the left side. It may be used to set the position for a label moving above the chart:

Common issues and solutions

The chart is not showing

The Chart class inherits from UIView, so if your chart is not displaying it is likely a problem related to the view's size. Check your view constraints and make sure you initialize it on viewDidLoad, when UIKit can calculate the view dimensions.

Some tips for debugging an hidden chart:

• start your app and then debug the UI Hierarchy from the Debug navigator
• initialize a simple UIView with a colored background instead of the chart to easily see how the view is positioned
• try to not to nest the chart in a subview for better debugging

How do I update the chart series?

There is no built-in method to update a chart. To accomplish this:

1. remove the old series
2. add the updated one
3. call setNeedsDisplay to refresh the chart

Reference

Chart class

Chart options

• areaAlphaComponent: alpha factor for the area’s color.
• axesColor: the axes’ color.
• bottomInset: height of the area at the bottom of the chart, containing the labels for the x-axis.
• delegate: the delegate for listening to touch events.
• highlightLineColor: color of the highlight line.
• highlightLineWidth: width of the highlight line.
• gridColor: the grid color.
• labelColor: the color of the labels.
• labelFont: the font used for the labels.
• lineWidth: width of the chart’s lines.
• maxX: custom maximum x-value.
• maxY: custom maximum y-value.
• minX: minimum x-value.
• minY: minimum y-value.
• topInset: height of the area at the top of the chart, acting a padding to make place for the top y-axis label.
• xLabelsFormatter: formats the labels on the x-axis.
• xLabelsTextAlignment: text-alignment for the x-labels.
• yLabelsFormatter: formats the labels on the y-axis.
• yLabelsOnRightSide: place the y-labels on the right side.

Methods

• add(series: ChartSeries): add a series to the chart.
• removeSeries(): remove all the series from the chart.
• removeSeriesAtIndex(index: Int): remove a series at the specified index.
• valueForSeries(): get the value of the specified series at the specified index.

ChartSeries class

• area: draws an area below the series’ line.
• line: set it to false to hide the line (useful for drawing only the area).
• color: the series color.
• colors: a touple to specify the color above or below the zero. For example, (above: ChartsColors.redColor(), below: ChartsColors.blueColor(), -4) will use red for values above -4, and blue for values below -4.

License

SwiftChart is available under the MIT license. See the LICENSE file for more info.