When you update your data with the new readings, are you only updating one of the two series? I think the reason you're not seeing any updates might be because of this. When the chart shows multiple series it expects them to have the same number of data points and will fall back on the lowest point count. Try adding readings to both series, or if there isn't a valid value to add, add a nan to the other series.

Using refresh forces the chart to update everything, which is more suitable when the entire datasource changes, but should still work here. The slowdown could indicate a memory leak, but this will require some profiling.

It looks like your example is using the same x and y axes for both series, whereas my chart is plotting the values for each series on its own y-axis (one is a value and one is a percentage, so they don't use the same scale). So maybe that's why yours works and mine doesn't?

Is there something special I need to do when using different axes? I tried creating them with separate y-axes but sharing the same x-axis, but then one of the line series just didn't show up at all, and the one that did get drawn still didn't update with new values.

Separate Y axes shouldn't make a difference. This new code will put 2 separate Y axes in the chart, each with a different range.

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    _chartData = [[NSMutableArray alloc]init];
    
    _dsh1 = [[IGCategoryDateSeriesDataSourceHelper alloc]initWithData:_chartData valuePath:@"value1" andDatePath:@"date1"];
    _dsh2 = [[IGCategoryDateSeriesDataSourceHelper alloc]initWithData:_chartData valuePath:@"value2" andDatePath:@"date2"];
    
    _chart = [[IGChartView alloc]initWithFrame:self.view.bounds];
    _chart.delegate = self;
    [_chart addSeriesForType:[IGLineSeries class] usingKey:@"series1" withDataSource:_dsh1 firstAxisKey:@"x" secondAxisKey:@"y1"];
    [_chart addSeriesForType:[IGLineSeries class] usingKey:@"series2" withDataSource:_dsh2 firstAxisKey:@"x" secondAxisKey:@"y2"];
    
    IGNumericYAxis *y1 = (IGNumericYAxis*)[_chart findAxisByKey:@"y1"];
    y1.labelsLocation = IGAxisLabelsLocationOutsideLeft;
    y1.minimum = 0;
    y1.maximum = 10;
    
    IGNumericYAxis *y2 = (IGNumericYAxis*)[_chart findAxisByKey:@"y2"];
    y2.labelsLocation = IGAxisLabelsLocationOutsideRight;
    y2.minimum = 10;
    y2.maximum = 100;
    
    y2.majorStrokeThickness = 0;
    
    [self.view addSubview:_chart];
    
    _timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTick) userInfo:nil repeats:YES];
}

-(void)timerTick
{
    ChartData *obj = [[ChartData alloc]init];
    obj.date1 = obj.date2 = [NSDate new];
    obj.value1 = arc4random()%10;
    obj.value2 = arc4random()%90 + 10;
    [_chartData addObject:obj];
    
    NSInteger index = _chartData.count-1;
    [_chart insertItemAtIndex:index withSource:_dsh1];
    [_chart insertItemAtIndex:index withSource:_dsh2];
}

OK thanks, glad I'm not crazy. I'll try it out using the refresh() method with fewer data points.

Could've sworn this worked in earlier versions of Swift, but you're right, the data in the DSH and chartData arrays are not the same. You might have to resort to calling refresh on the chart instead of insert.

I've rewritten my code from your example, and now the graph is adding new points. However, all of the values are 0.

Graph creation:

graph = IGChartView.init(frame: CGRect.init(x: 0, y: 0, width: container.frame.width, height: container.frame.height))
   graph.autoresizingMask = [UIViewAutoresizing.flexibleHeight, UIViewAutoresizing.flexibleWidth]
 graph.theme = IGChartDefaultThemes.defaultTheme()
   graph.gridMode = IGGridMode.behindSeries
graph.zoomDisplayType = IGChartZoom.horizontal
        
        temperatureDataSource = IGCategoryDateSeriesDataSourceHelper.init(data: bleManager.coolantTempReadings, valuePath: "value", andDatePath: "date")
        doorDataSource = IGCategoryDateSeriesDataSourceHelper.init(data: bleManager.coolantDoorReadings, valuePath: "value", andDatePath: "date")
        graph.delegate = self
        graph.addSeries(forType: IGLineSeries.self, usingKey: "tempSeries", with: temperatureDataSource, firstAxisKey: "x", secondAxisKey: "tempY")
        graph.addSeries(forType: IGLineSeries.self, usingKey: "doorSeries", with: doorDataSource, firstAxisKey: "x", secondAxisKey: "doorY")
        
        let tempY: IGNumericYAxis = graph.findAxis(byKey: "tempY") as! IGNumericYAxis
        tempY.labelsLocation = IGAxisLabelsLocation.outsideLeft
        tempY.minimum = 0
        tempY.maximum = 140
        
        let doorY: IGNumericYAxis = graph.findAxis(byKey: "doorY") as! IGNumericYAxis
        doorY.labelsLocation = IGAxisLabelsLocation.outsideRight
        doorY.minimum = 0
        doorY.maximum = 100
        doorY.majorStrokeThickness = 0
    
        graphContainer.addSubview(graph)

When new values come in:

graph.insertItem(at: bleManager.coolantTempReadings.count - 1, with: temperatureDataSource)
        

graph.insertItem(at: bleManager.coolantDoorReadings.count - 1, with: doorDataSource)

I'm logging the values to the console, they aren't 0. It seems that the datasources values aren't getting updated when their associated data object is. Maybe it's an objective-c to swift translation issue?