NSInvalidArgumentException，理由：'-[NSNull isEqualToString:]

Question

我收到了推送通知，并试图按下面的方式解析字典，但我得到了以下异常。

*由于“NSInvalidArgumentException”异常终止应用程序，原因：'-NSNull isEqualToString:：未识别的选择器发送到实例0x1a6574ef8‘

这是我收到的字典

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Implementation

-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
    if (application.applicationState == UIApplicationStateActive)
    {
       // exception happens the following line
        if([[userInfo objectForKey:@"aps"] objectForKey:@"alert"] != NULL && 
           [[[userInfo objectForKey:@"aps"] objectForKey:@"alert"]isEqualToString:@"New Order!"])
        {
            [[NSNotificationCenter defaultCenter] postNotificationName: @"newOrderNotificationMessage" object: [userInfo objectForKey:@"aps"]];
        }
}

Answer 1

您还需要检查NSNull类，尝试使用以下方法

-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
    if (application.applicationState == UIApplicationStateActive)
    {
        // exception happens the following line
        if([[userInfo objectForKey:@"aps"] objectForKey:@"alert"] != NULL && [[[userInfo objectForKey:@"aps"] objectForKey:@"alert"] class] != [NSNull class]){
            if ([[[userInfo objectForKey:@"aps"] objectForKey:@"alert"]isEqualToString:@"New Order!"])
            {
                [[NSNotificationCenter defaultCenter] postNotificationName: @"newOrderNotificationMessage" object: [userInfo objectForKey:@"aps"]];
            }
        }

    }
}

希望这能有所帮助