The main use of a pie chart is to show comparison. When items are presented on a pie chart, you can easily see which item is the most popular and which is the least popular.

you can create the pie chart in iOS by using the following methods. Here we use the core Plot framework .First we have to create the model class for the data that we want to display in our pie chart and then use these methods.some delegates are also available to customize the chart like different color for different section of pie chart.

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    (void)initPlot {
        [self configureHost];
        [self configureGraph];
        [self configureChart];
        [self configureLegend];
    }

    -(void)configureHost {
        CGRect parentRect = self.view.bounds;
        CGSize toolbarSize = self.toolbar.bounds.size;
        parentRect = CGRectMake(parentRect.origin.x,
                                (parentRect.origin.y + toolbarSize.height),
                                parentRect.size.width,
                                (parentRect.size.height - toolbarSize.height));
        // 2 - Create host view
        self.hostView = [(CPTGraphHostingView *) [CPTGraphHostingView alloc] initWithFrame:parentRect];
        self.hostView.allowPinchScaling = YES;
        [self.view addSubview:self.hostView];
    }

    -(void)configureGraph {
        CPTGraph *graph = [[CPTXYGraph alloc] initWithFrame:self.hostView.bounds];
        self.hostView.hostedGraph = graph;
        graph.paddingLeft = 0.0f;
        graph.paddingTop = 0.0f;
        graph.paddingRight = 0.0f;
        graph.paddingBottom = 0.0f;
        graph.axisSet = nil;
        // 2 - Set up text style
        CPTMutableTextStyle *textStyle = [CPTMutableTextStyle textStyle];
        textStyle.color = [CPTColor grayColor];
        textStyle.fontName = @"Helvetica";
        textStyle.fontSize = 16.0f;
        // 3 - Configure title
        NSString *title = @"Pie-Chart";
        graph.title = title;
        graph.titleTextStyle = textStyle;
        graph.titlePlotAreaFrameAnchor = CPTRectAnchorTop;
        graph.titleDisplacement = CGPointMake(0.0f, -12.0f);
        // 4 - Set theme
        self.selectedTheme = [CPTTheme themeNamed:kCPTPlainWhiteTheme];
        [graph applyTheme:self.selectedTheme];
    }

    -(void)configureChart {
        // 1 - Get reference to graph
        CPTGraph *graph = self.hostView.hostedGraph;
        // 2 - Create chart
        CPTPieChart *pieChart = [[CPTPieChart alloc] init];
        pieChart.dataSource = self;
        pieChart.delegate = self;
        pieChart.pieRadius = (self.hostView.bounds.size.height * 0.5) / 2; //set the radius of pie circle
        pieChart.identifier = graph.title;
        pieChart.startAngle = M_PI_4;
        pieChart.sliceDirection = CPTPieDirectionClockwise;
        // 3 - Create gradient
        CPTGradient *overlayGradient = [[CPTGradient alloc] init];
        overlayGradient.gradientType = CPTGradientTypeRadial;
        overlayGradient = [overlayGradient addColorStop:[[CPTColor blackColor] colorWithAlphaComponent:0.0] atPosition:0.9];
        overlayGradient = [overlayGradient addColorStop:[[CPTColor blackColor] colorWithAlphaComponent:0.4] atPosition:1.0];
        pieChart.overlayFill = [CPTFill fillWithGradient:overlayGradient];
        // 4 - Add chart to graph    
        [graph addPlot:pieChart];
    }

    -(void)configureLegend {
        // 1 - Get graph instance
        CPTGraph *graph = self.hostView.hostedGraph;
        // 2 - Create legend
        CPTLegend *theLegend = [CPTLegend legendWithGraph:graph];
        // 3 - Configure legend
        theLegend.numberOfColumns = 1;
        theLegend.fill = [CPTFill fillWithColor:[CPTColor whiteColor]];
        theLegend.borderLineStyle = [CPTLineStyle lineStyle];
        theLegend.cornerRadius = 5.0;
        // 4 - Add legend to graph
        graph.legend = theLegend;
        graph.legendAnchor = CPTRectAnchorRight;
        CGFloat legendPadding = -(self.view.bounds.size.width / 10);
        graph.legendDisplacement = CGPointMake(legendPadding, 80.0);
    }