01、UIPickerView-案例2

省市联动案例

1、创建模型-(instancetype) initWithDict: (NSDictionary *) dict{    if(self=[super init]){        [self setValuesForKeysWithDictionary:dict];    }    return self;}+(instancetype) provinceVoWithDict: (NSDictionary *) dict{    return [[self alloc] initWithDict:dict];}

2、搭建界面和拖拽连线数据源和代理到控制器

3、懒加载数据-(NSArray *)provinces{    if(_provinces==nil){        NSString *path=[[NSBundle mainBundle] pathForResource:@"cities.plist" ofType:nil];        NSArray *dictArray=[NSArray arrayWithContentsOfFile:path];        NSMutableArray *mArray=[NSMutableArray arrayWithCapacity:dictArray.count];        for(NSDictionary *dict in dictArray){            [mArray addObject:[ProvinceVO provinceVoWithDict:dict]];        }        _provinces=mArray;    }    return _provinces;}4、实现数据源方法-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{    return 2;}-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{    //第一组就是数组的长度    if(component==0){        return [self.provinces count];    }else{//第二组就是第一组选中的行对应的省份的所有市        NSInteger selRow=[self.pickerView selectedRowInComponent:0];        self.selProvinceVO=self.provinces[selRow];        return [self.selProvinceVO.cities count];    }}5、实现代理方法-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{    //第一组就是显示的数组里的元素    if(component==0){        return [self.provinces[row] name];    }else{//第二组就是显示选中第一组的行所对应的省份对应的所有市        return self.selProvinceVO.cities[row];    }}-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{    //只有选择第一组的时候，第二组才会跟着联动    if(component==0){        [self.pickerView reloadComponent:1];        [self.pickerView selectRow:0 inComponent:1 animated:YES];    }    NSInteger selRow=[self.pickerView selectedRowInComponent:0];    NSInteger selRow2=[self.pickerView selectedRowInComponent:1];    //更新Label    self.provinceLabel.text=[self.provinces[selRow] name];    self.cityLabel.text=self.selProvinceVO.cities[selRow2];}6、默认选中第一行- (void)viewDidLoad {    [super viewDidLoad];    //默认选中第一行    [self pickerView:self.pickerView didSelectRow:0 inComponent:0];}7、城市选择bug修复要全局共用选择好了的省份@property (nonatomic,strong) ProvinceVO *selProvinceVO;//第一组选中的第一行8、注意因为省市是关联的，所以代理方法didSelectRow中的城市选择是根据选中了的行数来展示方法参数中的row是会根据省或者市滑动而变化，会造成下标越界，只能根据 NSInteger selRow2=[self.pickerView selectedRowInComponent:1];  self.cityLabel.text=self.selProvinceVO.cities[selRow2];