界面通信之属性传值、代理传值

//属性传值
- (void)sendValue {
    SecondViewController *secondVC = [[SecondViewController alloc] init];
    secondVC.string = _textField.text;//这句是属性传值的核心，在需要接收值的界面声明一个字符串属性接受值
    secondVC.color = self.view.backgroundColor;
    [self.navigationController pushViewController:secondVC animated:YES];
    [secondVC release];
    
}

//1、声明协议,代理传值用于从后往前传值，所以后者应该是协议的拥有者，在后面的界面声明协议
//UI中的协议名称为 当前类名 + Delegate
@protocol FourthViewControllerDelegate <NSObject>

- (void)pushValue:(NSString *)text color:(UIColor *)color;

@end

//2、声明代理
@property (nonatomic, assign) id<FourthViewControllerDelegate> delegate;

//3、执行协议方法
- (void)back {
    if (self.delegate != nil && [self.delegate respondsToSelector:@selector(pushValue:color:)]) {
        [self.delegate pushValue:self.textField.text color:self.view.backgroundColor];
    }
    
    [self.navigationController popViewControllerAnimated:YES];
}

//4、接收协议  接受协议的应该是需要接收值的界面，红色部分便是接收协议
@interface ThirdViewController : UIViewController<FourthViewControllerDelegate>
@end

//5、设置代理

- (void)next {

    FourthViewController *fourthVC = [[FourthViewController alloc] init];

    fourthVC.delegate = self;//指定第四个界面的代理对象为第三个视图控制器

    [self.navigationController pushViewController:fourthVC animated:YES];

    [fourthVC release];

}

//6、实现代理方法

- (void)pushValue:(NSString *)text color:(UIColor *)color {

    self.label.text = text;

    self.view.backgroundColor = color;

}