title: Warning while executing code for CorePlot
body: <pre><code>- (void)viewDidLoad
  {
  graph = [[CPTXYGraph alloc] initWithFrame: self.view.bounds];   
  CPTGraphHostingView *hostingView = (CPTGraphHostingView *)self.view;
  hostingView.hostedGraph = graph;
  CPTPieChart *pieChart = [[CPTPieChart alloc] init];
  pieChart.dataSource = self;
  pieChart.pieRadius = 100.0;
  pieChart.identifier = @"PieChart1";
  pieChart.startAngle = M_PI_4;
  pieChart.sliceDirection = CPTPieDirectionCounterClockwise;
  
  self.pieData=   [NSMutableArray arrayWithObjects:[NSNumber numberWithDouble:90.0], 
                  [NSNumber numberWithDouble:20.0],
                  [NSNumber numberWithDouble:30.0],
                  [NSNumber numberWithDouble:40.0],
                  [NSNumber numberWithDouble:50.0], 
                  [NSNumber numberWithDouble:60.0], nil];
  
  CPTTheme *theme = [CPTTheme themeNamed:kCPTDarkGradientTheme];
  [graph applyTheme:theme];
  [graph addPlot:pieChart];
  [pieChart release];
  }
  </code></pre>
  
  <p>I found this code on the net.This Code is working fine but am getting two warnings at<br>
        <code>pieChart.dataSource = self;</code></p>
  
  <p>It says.</p>
  
  <blockquote>
    <p>warning: class 'SOTC_CorePlotExampleViewController' does not
    implement the 'CPTPlotDataSource' protocol</p>
    
    <p>warning: Semantic Issue: Assigning to 'id' from
    incompatible type 'SOTC_CorePlotExampleViewController *'</p>
  </blockquote>