Question

我正在开发一个混合语言项目，在XCode 6中结合了Objective C和Swift。

在这个项目中，Singleton（Objective C）类发布一个通知，然后由ViewController（Swift）接收。

Singleton.h

#import <Foundation/Foundation.h>

NSString *const notificationString = @"notificationString";

@interface Singleton : NSObject

+ (id)sharedSingleton;

- (void)post;

@end

Singleton.m

#import "Singleton.h"

static Singleton *shared = nil;

@implementation Singleton

- (id)init {
    self = [super init];
    if (self) {

    }
    return self;
}

#pragma mark - Interface

+ (Singleton *)sharedSingleton {
    static dispatch_once_t pred;

    dispatch_once(&pred, ^{
        shared = [[Singleton alloc] init];
    });

    return shared;
}

- (void)post {
    char bytes[5] = {5, 7, 9, 1, 3};

    NSDictionary *objects = @{@"device":[NSData dataWithBytes:bytes length:5], @"step1":[NSNumber numberWithInt:4], @"step2":[NSNumber numberWithInt:7]};

    [[NSNotificationCenter defaultCenter] postNotificationName:notificationString
                                                        object:self
                                                      userInfo:objects];
}

@end

当然，在这个混合语言项目中，必须正确设置桥接标头（只需在其中添加#import "Singleton.h"）

ViewController.swift

import UIKit

class ViewController: UIViewController {

    let singleton = Singleton.sharedSingleton() as Singleton

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        NSNotificationCenter.defaultCenter().addObserver(self, selector: "action:", name: notificationString, object: nil)

        singleton.post()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.


    }

    // MARK: - Notification

    func action(notification: NSNotification) {
        let userInfo = notification.userInfo as Dictionary<String, String> // things go wrong here?!
        let hash = userInfo["device"]
        let completed = userInfo["step1"]
        let total = userInfo["step2"] 

    }

}

这不会导致编译错误。但是，在运行时，XCode报告：

致命错误：无法从Objective-C桥接字典

notification.userInfo包含由NSSTring: NSData，NSSTring: NSNumber，NSSTring: NSNumber构建的NSDictionary，而此命令let userInfo = notification.userInfo as Dictionary<String, String>正在尝试转换为Dictionary<String, String>

这是否会导致致命错误？

在ViewController.swift中，我应该怎么做才能“阅读”从notification.userInfo发送的Singleton.m传递的NSDictionary？

提前致谢

Answer 1

尝试这样做

let userInfo = notification.userInfo as Dictionary<String, AnyObject>

如您所示，userInfo字典包含NSData，NSNUmber表示值。

在混合语言项目中提取通知userinfo

1 个答案: