Ios 核心图动态集xPlotRange

我有一个图形，我需要在添加新元素的过程中更改它的xPlotRange。我怎么做

我试过这个：

[self.hostView.hostedGraph.defaultPlotSpace 

setAllowsUserInteraction:YES];

---

long count=[array count]；
如果（计数>100&&count）
long count = [array count];
if (count>100 && count<maxElements)
[self plotSpace:self.hostView.hostedGraph.defaultPlotSpace willChangePlotRangeTo:[CPTMutablePlotRange plotRangeWithLocation:@(0.0) length:[NSNumber numberWithInteger:count+100]] forCoordinate:CPTCoordinateX];

CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace*)self.graph.defaultPlotSpace; plotSpace.allowsUserInteraction=YES; plotSpace.delegate = self;

plotSpace.xRange = [CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromInt(xAxisMin)/*minimum x value*/ lengthDecimal:CPTDecimalFromInt()];

plotSpace.yRange = [CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromInt(60) lengthDecimal:CPTDecimalFromInt(yAxisRange)];

[plotSpace setGlobalXRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromInt(0) lengthDecimal:CPTDecimalFromInt(xAxisMax - xAxisMin)]];

[plotSpace setGlobalYRange:[CPTPlotRange plotRangeWithLocationDecimal:CPTDecimalFromInt([[_dict1 objectForKey:@"minValue"]intValue ]) lengthDecimal:CPTDecimalFromInt(yAxisRange)]];