Question

我试图获得两点之间的预设里程（school1＆amp; school2）。我写的名为“getMileage”的方法使用MagicalRecord正常工作，从我的CoreData中获取正确的里程（例如PointA到PointB是2.6英里）

我有一个带有2个组件的选择器 - 当用户从选择器中选择一个位置的名称时，我希望我的里程标签更新为适当的值（2.6,3.1,4.0，无论从数据库返回什么）

最初它加载正常 - 因为getMileage方法中的数组设置为空，因为没有在选择器上进行选择。一旦选择器选择了某个东西，它就会抛出一个错误，指出：

2014-02-18 10:31:41.345 54 Miles[18618:70b] Our result miles are: (
    "2.6"
)
2014-02-18 10:31:41.345 54 Miles[18618:70b] -[__NSArrayI length]: unrecognized selector sent to instance 0x8a16690
2014-02-18 10:31:41.349 54 Miles[18618:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayI length]: unrecognized selector sent to instance 0x8a16690'
*** First throw call stack:

如您所见 - NSLog显示从我的getMileage方法返回的相应里程。

以下是我的选择器的didSelectRow方法：

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if (_tripPicker) {
        if (component == 0){
            //Get Mileage array
            NSArray *currentMiles = [self getMileage];
            //Update Labels
            begSchoolLabel.text = [_schoolArray1 objectAtIndex:row];
            _milesLabel.text = [currentMiles valueForKey:@"miles"];
        }
        if (component == 1){
            //Get Mileage array
            NSArray *currentMiles = [self getMileage];
            //Update Labels
            endSchoolLabel.text = [_schoolArray2 objectAtIndex:row];
            _milesLabel.text = [currentMiles valueForKey:@"miles"];
        }


    }
}

这是我的getMileage方法：

- (NSArray *)getMileage {
    //Update the Mileage indicator to display miles between currently selected values
    NSString *begSchool = [_schoolArray1 objectAtIndex:[_tripPicker selectedRowInComponent:0]];
    NSString *endSchool = [_schoolArray1 objectAtIndex:[_tripPicker selectedRowInComponent:1]];
    NSPredicate *milesFilter = [NSPredicate predicateWithFormat:@"beg_school=%@ AND end_school=%@", begSchool, endSchool];
    NSArray *resultMiles = [MetaMiles MR_findAllWithPredicate:milesFilter];
    if (!resultMiles || ![resultMiles count]) {
        //The first load - this displays appropriately in log letting us know there is currently nothing there
        NSLog(@"Empty Array");
    } else {
        //This confirms our result miles come out appropriately - they look like this: ("2.1")
        NSLog(@"Our result miles are: %@", [resultMiles valueForKey:@"miles"] );
    }
    return resultMiles;
}

问题出在我的选择器的didSelectRow中 - 当试图为labelMiles分配标签时;就在它破裂的时候。

我也尝试过这个'didSelectRow'方法：

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if (_tripPicker) {
        if (component == 0){
            //Get Mileage array
            NSArray *currentMiles = [self getMileage];
            //Update Labels
            begSchoolLabel.text = [_schoolArray1 objectAtIndex:row];
            _milesLabel.text = [currentMiles objectAtIndex:0];
        }
        if (component == 1){
            //Get Mileage array
            NSArray *currentMiles = [self getMileage];
            //Update Labels
            endSchoolLabel.text = [_schoolArray2 objectAtIndex:row];
            _milesLabel.text = [currentMiles objectAtIndex:0];
        }


    }
}

这也开启了这个错误：

2014-02-18 10:44:02.099 54 Miles[18635:70b] Our result miles are: (
    "2.6"
)
2014-02-18 10:44:02.099 54 Miles[18635:70b] -[MetaMiles length]: unrecognized selector sent to instance 0x8ad3960
2014-02-18 10:44:02.103 54 Miles[18635:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[MetaMiles length]: unrecognized selector sent to instance 0x8ad3960'
*** First throw call stack:

我已经用了一段时间对抗这个问题并用Google搜索并搜索了答案，但却空手而归。

这可能是非常简单的我误解或不做。所有帮助表示赞赏！

Answer 1

您的代码

NSArray *resultMiles = [MetaMiles MR_findAllWithPredicate:milesFilter];
if (!resultMiles || ![resultMiles count]) {
    //The first load - this displays appropriately in log letting us know there is currently nothing there
    NSLog(@"Empty Array");
} else {
    //This confirms our result miles come out appropriately - they look like this: ("2.1")
    NSLog(@"Our result miles are: %@", [resultMiles valueForKey:@"miles"] );

这对我来说看起来像resultMiles不是一个数组（可能是一个字典），因为你使用valueForKey来获得结果，但是后来你使用的objectAtIndex失败了

无法使用方法中的数组数据正确更新标签

1 个答案: