objective c中具有双y轴的多个条形图

#import <CorePlot/CorePlot.h>

@interface ViewController : UIViewController<CPTPlotDataSource>

@property (nonatomic, strong) CPTGraphHostingView *hostingView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 创建图表视图
    self.hostingView = [[CPTGraphHostingView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:self.hostingView];
    
    // 创建图表对象
    CPTXYGraph *graph = [[CPTXYGraph alloc] initWithFrame:self.hostingView.bounds];
    self.hostingView.hostedGraph = graph;
    
    // 设置图表样式和属性
    // ...
    
    // 创建数据源
    graph.dataSource = self;
    
    // 创建条形图
    CPTBarPlot *barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor blueColor] horizontalBars:NO];
    barPlot.dataSource = self;
    
    // 设置条形图样式和属性
    // ...
    
    // 创建Y轴对象
    CPTXYAxis *yAxis1 = [[CPTXYAxis alloc] init];
    yAxis1.axisConstraints = [CPTConstraints constraintWithLowerOffset:0.0];
    // 设置Y轴1样式和属性
    // ...
    
    CPTXYAxis *yAxis2 = [[CPTXYAxis alloc] init];
    yAxis2.axisConstraints = [CPTConstraints constraintWithUpperOffset:0.0];
    // 设置Y轴2样式和属性
    // ...
    
    // 将条形图和Y轴对象添加到图表对象中
    [graph addPlot:barPlot];
    [graph addAxis:yAxis1];
    [graph addAxis:yAxis2];
}

#pragma mark - CPTPlotDataSource

- (NSUInteger)numberOfRecordsForPlot:(CPTPlot *)plot {
    // 返回条形图的数据数量
    // ...
}

- (NSNumber *)numberForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)index {
    // 返回条形图的数据值
    // ...
}

@end