首先添加UIPickerViewDelegate代理
在.h文件中添加

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@interface ViewController : UIViewController<UIPickerViewDelegate,UIPickerViewDataSource>

@property (weak, nonatomic) IBOutlet UIPickerView *pickerview;
@property (weak, nonatomic) IBOutlet UILabel *label;

@property (nonatomic,strong) NSDictionary *pickerData;
@property (nonatomic,strong) NSArray *proviencesData;
@property (nonatomic,strong) NSArray *cityData;
@end

//
//  ViewController.m
//  test_04
//
//  Created by frola on 2017/10/10.
//  Copyright © 2017年 frola. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
//   读取plist文件中的数据
    NSBundle *bundle = [NSBundle mainBundle];
    NSString *path = [bundle pathForResource:@"proven" ofType:@"plist"];
    NSDictionary *dic = [[NSDictionary alloc]initWithContentsOfFile:path];

    self.pickerData = dic;
    self.proviencesData = [_pickerData allKeys];
    
    NSString *selectProvience = [self.proviencesData objectAtIndex:0];
    self.cityData = [self.pickerData objectForKey:selectProvience];
    
    self.pickerview.dataSource = self;
    self.pickerview.delegate = self;
}
- (IBAction)getText:(id)sender {
    NSInteger row1 = [self.pickerview selectedRowInComponent:0];
    NSInteger row2 = [self.pickerview selectedRowInComponent:1];
    NSString *select1 = [self.proviencesData objectAtIndex:row1];
    NSString *select2 = [self.cityData objectAtIndex:row2];
    
    NSString *title = [NSString stringWithFormat:@"%@||%@",select1,select2];
    
    _label.text = title;
    
}


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

-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
    return 2;
}

- (NSInteger)pickerView:(nonnull UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    if (component == 0) {
        return _proviencesData.count;
    }else{
        return _cityData.count;
    }
    return  0;
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
    if (component==0) {
        return [self.proviencesData objectAtIndex:row];
    }else{
        return [self.cityData objectAtIndex:row];
    }
    return @"";
}
//切换省份后，城市刷新
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
    if (component == 0) {
        NSString *selectProvience = [self.proviencesData objectAtIndex:row];
        self.cityData = [self.pickerData objectForKey:selectProvience];
        [self.pickerview reloadComponent:1];
    }
    
    
}
@end

省份数据添加在plist文件中

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