通過代理 delegate

VCSecond。h

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

//定義一個協議 檢視控制器二協議
@protocol VCSecondDelegate <NSObject>
//定義一個協議函式，改變背景顏色
-(void) changecolor:(UIColor*) color;

@end


@interface VCSecond : UIViewController
// 定義一個代理物件
//代理物件執行協議函式
//通過代理物件實現協議函式 達到代理物件改變本身屬性的目的
//代理物件一定要實現代理協議
 



@property (assign,nonatomic)NSInteger tag;
@property (assign,nonatomic)id<VCSecondDelegate> delegate;


@end

VCSecond。m

#import "VCSecond.h"

@interface VCSecond ()

@end

@implementation VCSecond

- (void)viewDidLoad {
    [super viewDidLoad];
    UIBarButtonItem* btn= [[UIBarButtonItem alloc] initWithTitle:@"
 
change color" style:UIBarButtonItemStyleDone target:self action:@selector(pressesChanged)];
    self.navigationItem.rightBarButtonItem=btn;
}

-(void)pressesChanged{
//   代理物件呼叫事件操作
    [_delegate changecolor:[UIColor redColor]];
    
    
    
    
}



@end

VCFirst。h

#import <UIKit/UIKit.h>
#import
 
 "VCSecond.h"


NS_ASSUME_NONNULL_BEGIN

@interface VCFirst : UIViewController
-(void) changecolor:(UIColor*) color;

@end

NS_ASSUME_NONNULL_END

#import <UIKit/UIKit.h>
#import "VCSecond.h"


NS_ASSUME_NONNULL_BEGIN

@interface VCFirst : UIViewController
-(void) changecolor:(UIColor*) color;

@end

NS_ASSUME_NONNULL_END

VCFirst。m

#import "VCFirst.h"
#import "VCSecond.h"
@interface VCFirst ()

@end

@implementation VCFirst

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    
    
}
-(void) touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    
    VCSecond* vc= [[VCSecond alloc] init];
//    將當前控制器作為代理物件賦值
    vc.delegate=self;
    
    vc.view.backgroundColor = [UIColor orangeColor];
    [self.navigationController pushViewController:vc animated:YES];
    
    
}


-(void)changecolor:(UIColor *)color
{
    
    self.view.backgroundColor = color;
    
}


@end