#import "ViewController.h"

@interface ViewController () <UIPickerViewDelegate, UIPickerViewDataSource>

/**
 * plist对应的字典
 */
@property (nonatomic, strong) NSDictionary* cityNames;
/**
 * 省份
 */
@property (nonatomic, strong) NSArray* provinces;
/**
 * 城市
 */
@property (nonatomic, strong) NSArray* cities;

@end

@implementation ViewController

/**
 * 懒加载plist
 *
 * @return plist对应的字典
 */
- (NSDictionary*)cityNames
{
  if (_cityNames == nil) {

    NSString* path = [[NSBundle mainBundle] pathForResource:@"cityData" ofType:@"plist"];

    _cityNames = [NSDictionary dictionaryWithContentsOfFile:path];
  }

    return _cityNames;
}

/**
 * 懒加载省份
 *
 * @return 省份对应的数组
 */
-(NSArray *)provinces
{
  if (_provinces == nil) {

    //将省份保存到数组中
    _provinces = [self.cityNames allKeys];


  }

  return _provinces;

}

- (void)viewDidLoad
{
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}

/**
 * 返回每一列的行数
 *
 * @param pickerView
 * @param component
 *
 * @return
 */
- (NSInteger)pickerView:(UIPickerView*)pickerView numberOfRowsInComponent:(NSInteger)component
{

  if (component == 0) {
    return self.provinces.count;
  }
  else {

    [self loadData:pickerView];

    return self.cities.count;
  }
}

/**
 * 返回每一行显示的文本
 *
 * @param pickerView
 * @param row
 * @param component
 *
 * @return
 */
- (NSString*)pickerView:(UIPickerView*)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{

  //第一列返回所有的省份
  if (component == 0) {
    return self.provinces[row];
  }
  else {

    [self loadData:pickerView];

    return self.cities[row];
  }
}


/**
 * 加载第二列显示的数据
 *
 * @param pickerView
 */
-(void)loadData:(UIPickerView*)pickerView
{

  //一定要首先获取用户选择的那一行 然后才可以根据选中行获取省份 获取省份以后再去字典中加载省份对应的城市
  NSInteger selRow = [pickerView selectedRowInComponent:0];

  NSString *key = self.provinces[selRow];

  self.cities = [self.cityNames valueForKey:key];

}

/**
 * 一共多少咧
 *
 * @param pickerView
 *
 * @return
 */
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView*)pickerView
{
  return 2;
}

/**
 * 选中某一行后回调 联动的关键
 *
 * @param pickerView
 * @param row    用户选择的省份
 * @param component
 */
- (void)pickerView:(UIPickerView*)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{

  if (component == 0) {

    //重新加载第二列的数据
    [pickerView reloadComponent:1];
    //让第二列归位
    [pickerView selectRow:0 inComponent:1 animated:YES];
  }
}

@end