无法将数据传递给控制器​​；为什么它不起作用？

Question

我看到另一个问题并研究了， 但无法传递数据。

这是我的代码。

1. 在HomeViewController.h

   @protocol homeViewControllerDelegate <NSObject>
   -(void)addItemViewController:(Float32)item;
   @end
   

   @interface HomeViewController : UIViewController @属性（非原子，保留）id 委托；

2. 在HomeViewController.mm

   #import "HomeViewController.h"
       static HomeViewController *mainController = nil; 
   
   #pragma mark MAIN CALLBACK
   void monoAudioCallback( Float32 * buffer, UInt32 frameSize, void * userData )
   {
       dispatch_async(dispatch_get_main_queue(), ^{
               [homeOsciView setDataMaxValue:fftMaxVal minValue:0]; 
               [homeOsciView addAndDrawData:fftData lenght:length];
               if(fftMaxVal >=0){
               [mainController.delegate addItemViewController:fftMaxVal];
                }
              [homeOsciView addAndDrawUILabelHz: HZ];
            });
   }
       viewDidLoad{
        mainController = self;
    }
   

3. 在graphViewController.h

   @interface GraphViewController : UIViewController<homeViewControllerDelegate>
   -(void)addItemViewController:(Float32)item;
   

4. 在graphViewController.m

       viewDidLoad(){
       homevc = [[HomeViewController alloc]init];
               homevc.delegate = self;
   }
   
       -(void)addItemViewController:(Float32)item{
           self.testdata = item;
           printf("thisis graphView data : %f\n",self.testdata);
       }
   

我想绘制 HomeViewController 将数据传递给 graphViewController 的图形，但是这段代码没有报错，但也不起作用。

我不知道问题。

你能帮帮我吗？

Answer 1

为了确保您理解我的意见，我为您编写了一个示例委托流程的演示应用程序。

AppDelegate.m

#import "GraphViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    // Override point for customization after application launch.


    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];

    self.window.rootViewController = [[GraphViewController alloc] init];

    [self.window makeKeyAndVisible];

    return YES;
}

...

GraphViewController.h

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

@interface GraphViewController : UIViewController <HomeViewControllerDelegate>

@property (nonatomic, strong) HomeViewController *homeVC;

@property (nonatomic, assign) Float32 data;

@end

GraphViewController.m

#import "GraphViewController.h"

@interface GraphViewController ()

@end

@implementation GraphViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    self.view.backgroundColor = [UIColor purpleColor];

    self.homeVC = [[HomeViewController alloc] init];
    self.homeVC.delegate = self;

    NSLog(@"presenting homeVC in 2 seconds...");

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{

        [self presentViewController:self.homeVC animated:YES completion:^{
            NSLog(@"homeVC presented, you should get data in 3 seconds...");
        }];

    });
}

-(void)addItem:(Float32)item
{
    self.data = item;
    NSLog(@"Graph view data: %f", self.data);
}

@end

HomeViewController.h

#import <UIKit/UIKit.h>

@protocol HomeViewControllerDelegate <NSObject>

-(void)addItem:(Float32)item;

@end




@interface HomeViewController : UIViewController

@property (nonatomic, weak) id<HomeViewControllerDelegate> delegate;

@end

HomeViewController.m

#import "HomeViewController.h"

@interface HomeViewController ()

@end

@implementation HomeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.


    self.view.backgroundColor = [UIColor redColor];

    // --------------------------------------------------------
    // simulate a callback by executing code after 3 seconds
    // --------------------------------------------------------
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{


        // good thing comes in pairs :D
        [self.delegate addItem:2.0];



    });
}

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



@end

我在控制台输出中得到了这个：

2015-08-28 16:20:53.021 AudioCallbackDemo[6973:194320] presenting homeVC in 2 seconds...
2015-08-28 16:20:55.534 AudioCallbackDemo[6973:194320] homeVC presented, you should get data in 3 seconds...
2015-08-28 16:20:58.044 AudioCallbackDemo[6973:194320] Graph view data: 2.000000