核心数据崩溃：在实体中找不到 NSInvalidArgumentException 键路径计数

问：

+ (NSArray *)retrievePercent{
    NSArray *percentResult = [NSArray arrayWithObjects:@"", nil];
    NSFetchRequest *fetchRequest = [NTSmartRegionGPS MR_createFetchRequest];
    
    NSString *entityName = [NTSmartRegionGPS MR_entityName];
    NSManagedObjectContext *context = [NSManagedObjectContext MR_context];
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityName
                                              inManagedObjectContext:context];
    //The query result displays the corresponding ssid value
    NSAttributeDescription *compactKeyDesc = [entity.attributesByName objectForKey:@"compactKey"];
    
    //Sum ssid columns
    NSExpression *compactKeyExpn = [NSExpression expressionForKeyPath:@"compactKey"];
    NSExpression *countExpn = [NSExpression expressionForFunction:@"count:" arguments:@[compactKeyExpn]];
    NSExpressionDescription *countExpnDesc = [[NSExpressionDescription alloc] init];
    countExpnDesc.name = @"count";
    countExpnDesc.expression = countExpn;
    //TODO Using NSInteger32AttributeType will cause the percentage resolution value to be abnormal, and the reason to be investigated
    countExpnDesc.expressionResultType = NSStringAttributeType;
    
    //The method is as follows: count() * 100/countOfEntity
    //(It is found in the actual measurement that the division result will be rounded. To get the proportion, multiply by 100 first)
    NSUInteger countOfEntity = [NTSmartRegionGPS MR_countOfEntities];
    if (countOfEntity <= 0) {
        return percentResult;
    }
    NSExpression *multiplierValueExpn = [NSExpression expressionForConstantValue:@(100)];
    NSExpression *multiplyExpn = [NSExpression expressionForFunction:@"multiply:by:" arguments:@[countExpn, multiplierValueExpn]];
    NSExpression *sumValueExpn = [NSExpression expressionForConstantValue:@(countOfEntity)];
    NSExpression *divideExpn = [NSExpression expressionForFunction:@"divide:by:" arguments:@[multiplyExpn, sumValueExpn]];
    NSExpressionDescription *percentExpnDesc = [[NSExpressionDescription alloc] init];
    percentExpnDesc.name = @"percent";
    percentExpnDesc.expression = divideExpn;
    //TODO Using NSInteger32AttributeType will cause the percentage resolution value to be abnormal, and the reason to be investigated
    percentExpnDesc.expressionResultType= NSStringAttributeType;
    
    
    fetchRequest.returnsObjectsAsFaults = false;
    fetchRequest.resultType = NSDictionaryResultType;
    fetchRequest.propertiesToFetch = @[compactKeyDesc, countExpnDesc, percentExpnDesc];
    fetchRequest.propertiesToGroupBy = @[@"compactKey"];
    //Use count results to sort in descending order
    NSSortDescriptor *sd = [NSSortDescriptor sortDescriptorWithKey:@"count" ascending:NO];
    fetchRequest.sortDescriptors = @[sd];
    @try {
        percentResult = [NTSmartRegionGPS MR_executeFetchRequest:fetchRequest];
    } @catch (NSException *exception) {
        // Fatal Exception: NSInvalidArgumentException keypath count not found in entity NTSmartRegionGPS
        DDLogError(@"Fetch gps region percent fail, exception:%@", exception.reason);
    }
    return percentResult;
}

NTSmartRegionGPS 是继承自 CoreData 的 NSManagedObject 对象。 上述函数实现了数据库中记录的组求和，然后计算百分比。

Crash 的监控记录显示以下行将 Crash：

percentResult = [NTSmartRegionGPS MR_executeFetchRequest:fetchRequest];

崩溃信息：致命异常：“NSInvalidArgumentException”，原因：“在实体中找不到键路径计数”

这段代码在我的iPhone12（真机）中测试过，它可以正常输出百分比结果（当数据库为空/有单条数据/有多条数据时），所以不知道为什么用户（%1-%2）会遇到崩溃。

谁能伸出援手;)？