Core Plot's CPTPlotSpaceDelegate: Correct implementation of zooming and panning
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I have implemented the delegates `CPTPlotDataSource` and `CPTPlotSpaceDelegate` in my view controller. I also have set `plotSpace.allowsUserInteraction = YES` and  `self.hostView.allowPinchScaling = YES`. 

However, the methods 

`-(BOOL)plotSpace:(CPTPlotSpace *)space shouldScaleBy:(CGFloat)interactionScale aboutPoint:(CGPoint)interactionPoint`, 

`-(BOOL)plotSpace:(CPTPlotSpace *)space shouldHandlePointingDeviceDownEvent:(id)event atPoint:(CGPoint)point`, 

`-(CGPoint)plotSpace:(CPTPlotSpace *)space willDisplaceBy:(CGPoint)proposedDisplacementVector` and 

`-(CPTPlotRange *)plotSpace:(CPTPlotSpace *)space willChangePlotRangeTo:(CPTPlotRange *)newRange forCoordinate:(CPTCoordinate)coordinate` are not called even though the plot is zoomable.

What did I miss in my code?

Thank you!