iOS基础控件UINavigationController中的传值

#import <UIKit/UIKit.h>

//声明一个协议

@protocol SendValue<NSObject>

//定义一个方法

- (void)sendBtnTitle:(NSString *)title;

@end

@interface FirstViewController : UIViewController

// 定义代理

@property (nonatomic, assign) id <SendValue>delegate;

// 创建一个正向传值的属性

@property (nonatomic,copy) NSString *currentTitle;

@end

- (void)didButton{
    NSArray *btntitles = [NSArray arrayWithObjects:@"按键一",@"按键二",@"按键三", nil];
    
    for (int i=0; i<btntitles.count; i++) {
        UIButton *btn = [UIButton buttonWithType:UIButtonTypeSystem];
        //改变按键字体颜色
        [btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
        [btn setTitle:[btntitles objectAtIndex:i] forState:UIControlStateNormal];
        // 如果按钮的标题和属性中的 _currentTitle 相同，即和根页面中的导航条的 title 一样 
        if([_currentTitle isEqualToString:btn.currentTitle]){
            //开启选中状态
            btn.selected = YES;
            btn.tintColor = [UIColor whiteColor];
        }

        [btn setTitleColor:[UIColor redColor] forState:UIControlStateSelected];
        [btn addTarget:self action:@selector(titlebtnClicked:) forControlEvents:UIControlEventTouchUpInside];
        btn.frame = CGRectMake(80, 140+60*i, self.view.frame.size.width-160, 40);
        btn.backgroundColor = [UIColor whiteColor];
        [self.view addSubview:btn];
    }
}

- (void)titlebtnClicked:(UIButton *)btn{
    
    
    NSString *title = btn.currentTitle;

    // 判断代理中是否有 sendBtnTitle ：这个函数

    if ([_delegate respondsToSelector:@selector(sendBtnTitle:)]){

        // 代理 执行自己的 sendBtnTitle 函数，传参是 title

       [_delegate sendBtnTitle:title];

    }

    NSLog(@"%@",title);
    [self.navigationController popViewControllerAnimated:YES];
    
}

#import <UIKit/UIKit.h>
#define C(a,b,c,d) [UIColor colorWithRed:a/255.0 green:b/255.0 blue:c/255.0 alpha:d/255.0]
#define IMG(name) [UIImage imageNamed:name]


#import "FirstViewController.h"
//将协议挂过来
@interface rootViewController : UIViewController<SendValue>

@end

- (void)btnClicked{
    FirstViewController *first = [[FirstViewController alloc] init];
    //将当前页面的navigationItem.title传递进去
    //正向传值
    first.currentTitle = self.navigationItem.title;
    //将代理指定为当前rootViewController类的指针
    first.delegate = self;
    [self.navigationController pushViewController:first animated:YES];
}

//实现协议定义的方法
- (void)sendBtnTitle:(NSString *)title{
    self.navigationItem.title = title;
}