ios - 如何访问其他类中的对象？

Question

我想从 ViewController 2 访问 ViewController 1 中的一个函数。这有效(通过断点和 NSLog 输出确认)。但是访问 ViewController 1 中定义的对象是 无 从 ViewController 2 调用时。

View Controller 1.h

#import "SRWebSocket.h"

@interface ViewController : UIViewController <UITextFieldDelegate, SRWebSocketDelegate> 
@property (nonatomic,strong) SRWebSocket *socket;

-(void)sendMessageToServerWithContent:(NSString *)message;

View Controller 1.m

- (IBAction)connect:(id)sender {

    socket.delegate = nil;
    socket = nil;

    socket = [[SRWebSocket alloc] initWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:serverIP_GLOBAL]]];

    socket.delegate = self;

}

-(void)sendMessageToServerWithContent:(NSString *)message{

//irrelevant code for question removed
[self.socket send:jsonString];

}

View Controller 2.h

#import "ViewController.h"

@property (nonatomic,strong) ViewController *viewVC;
@interface ContactsTableViewController : UITableViewController

View Controller 2.m

- (void)viewDidLoad {
    [super viewDidLoad];

    viewVC = [ViewController alloc];

    [viewVC sendMessageToServerWithContent:@"Test"]; 
    //When calling from here, the socket object in ViewController 1 is nil

}

Answer 1

您不能像这样初始化对象:viewVC = [ViewController alloc];
您必须将 ViewContoller1 的对象传递给 ViewContoller2，即

当您在 viewcontoller1 上推送 ViewContoller2 时，您已经编写了 Storyboard删除代码

 - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {

        ViewController2 *view2=[segue destinationViewController];
        view2.viewVC=self; // pass viewcontoller1 object to viewcontoller2
    }

而在 ViewContoller2 中，您将访问 viewVC 变量中的 viewContoller1 对象，您可以像这样直接调用它

- (void)viewDidLoad {

    [super viewDidLoad];
    [viewVC sendMessageToServerWithContent:@"Test"]; 
    //When calling from here, the socket object in ViewController 1 is nil

}