iphone - 由于未捕获的异常 'NSGenericException' 而终止应用程序，原因 : '*** Collection <__NSArrayM: 0x117540> was mutated while being enumerated

Question

当我的代码如下所示时，我遇到“集合在枚举时发生变化”异常:

NSString *poiStr = nil;
    int SuccessValue=0;
    NSMutableArray* poisArray=[[NSMutableArray alloc]init];
    for (id<MKAnnotation> annotation in mainMapView.annotations)
    {
        MKAnnotationView* anView = [mainMapView viewForAnnotation: annotation];
        if(anView)
        {

            POI* locationPOI = (POI*)[anView annotation];
            printf("\n Location poi shape groupId:%s=====%s",[locationPOI.shapeSpaceGroupId UTF8String],[poiStr UTF8String]);
            if((poiStr == nil) || ([poiStr isEqualToString:locationPOI.shapeSpaceGroupId]))
            {

                poiStr = locationPOI.shapeSpaceGroupId;
                [poisArray addObject:locationPOI];
                SuccessValue++;
            }
            printf("\n successValue:%d",SuccessValue);
            if(SuccessValue==2)
            {
                POI* poi=[poisArray objectAtIndex:0];
                [mainMapView removeAnnotation:poi];
                SuccessValue--;
            }

        }      

    }

任何人都可以建议我代码中有什么问题以及如何解决问题。

谢谢大家， 马丹。

Answer 1

基本上，您正在迭代列表的循环中修改列表。导致问题的行是:

[mainMapView removeAnnotation:poi];

当您迭代 mainMapView.annotations 时。一种可能的解决方案是将要删除的元素累积在不同的列表中，并在循环后将其删除。

根据您的代码，可能的解决方案是:

     NSString *poiStr = nil;
    int SuccessValue=0;
    NSMutableArray* poisArray=[[NSMutableArray alloc]init];
    NSMutableArray *to_delete = [[NSMutableArray alloc] init];
    for (id<MKAnnotation> annotation in mainMapView.annotations)
    {
        MKAnnotationView* anView = [mainMapView viewForAnnotation: annotation];
        if(anView)
        {

            POI* locationPOI = (POI*)[anView annotation];
            printf("\n Location poi shape groupId:%s=====%s",[locationPOI.shapeSpaceGroupId UTF8String],[poiStr UTF8String]);
            if((poiStr == nil) || ([poiStr isEqualToString:locationPOI.shapeSpaceGroupId]))
            {

                poiStr = locationPOI.shapeSpaceGroupId;
                [poisArray addObject:locationPOI];
                SuccessValue++;
            }
            printf("\n successValue:%d",SuccessValue);
            if(SuccessValue==2)
            {
                POI* poi=[poisArray objectAtIndex:0];
                //[mainMapView removeAnnotation:poi];
                [to_delete addObject:poi];
                SuccessValue--;
            }

        }      

    }
    for (id<MKAnnotation> annotation in to_delete)
           [mainMapView removeAnnotation:poi];

    [to_delete release];