iphone - 使用协议(protocol)和委托(delegate)在 View Controller 之间传递数据

Question

我正在尝试使用协议(protocol)和委托(delegate)将字符串文本从我的 viewcontroller 2 推送到 viewcontroller 1。我对这种传递数据的方法很陌生，所以如果我以任何方式显得无知，请原谅我。字符串颜色始终返回 null。我将发布目前为止的代码，如果有帮助，我将使用导航 Controller 并使用导航后退按钮从 ViewController 2 转到 ViewController 1。

View Controller 2

.h

@protocol PassString <NSObject>
@required
 - (void) setSecondFavoriteColor:(NSString *)string;
 @end
 @interface ViewController2 : UIViewController{
 UIButton *button; 
 NSString *ee
  id <PassString> delegate;
  }
  @property (retain) id delegate;

View Controller 2

.m

@synthesize delegate;   

-(void)button{
ee = @"Blue Color";
[[self delegate] setSecondFavoriteColor:ee];

View Controller 1.h

@interface ViewController1 : UIViewController <PassString>{
NSString*color;
 }
 @property (strong,nonatomic) NSString *color

View Controller 1.m

- (void)setSecondFavoriteColor:(NSString *)string
{
color = string;
NSLog(@"%@",color);
}

Answer 1

我在您的代码中注意到几件事，您的属性应包含指定的协议(protocol):

@property (retain) id <PassString> delegate;

在实现委托(delegate)方法的类中的某个时刻，您必须将委托(delegate)分配给 View Controller 1。例如:

[viewController2Instance setPassingDelegate:self];