如何将变量从一个视图控制器传递到另一个视图控制器？

Question

I have created a bottom slide up view controller for a main view controller, but I'm not sure how to pass information from the main view controller to the slide up one. I have a button in the main view controller that can show or hide the slide up view controller, and I want to use the button to pass information. The code below is the IBAction for the button which would show/hide the slide up view controller, but without a segue I'm not sure how to pass anything.

- (IBAction)btnMoveToShowBottomView:(id)sender {
    UIButton *button = sender;

    switch (button.tag) {
        case 0:
            [_delegate moveToHideBottomTableView];
            break;

        case 1:
           BottomTableViewController *tableScreen = [[BottomTableViewController alloc]...];
        tableScreen.photoDesc = selectedPhotoDesc;
        [_delegate moveToShowBottomTableView];
            break;

        default:
            break;
    }
}

In the code above I've tried to access the slide up view controller (with a class called BottomTableViewController), but there seems to be a problem because it is asking for an expected expression when I attempt to access an object in that class (an NSString called photoDesc).

Answer 1

You can use NSNotification mechanism:

In a controller that has to get param register for notification:

-(void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[NSNotificaitonCenter defaultCenter] addObserver: self selector:@selector(handleParam:) name:@"myNotification" object: nil];
}
- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}
- (void)handleParam:(NSNotification*)notification
{
    if ([notification.name isEqualToString:@"myNotification")
    {
        id myParam = notification.object;
    }
}

In a controller that has to send a parameter:

[[NSNotificationCenter defaultCenter] postNotificationName:@"myNotification" object: myObject];

Answer 2

Two options: 1) https://medium.com/@jigarm/nsuserdefaults-iphone-objective-c-514febbbf29b

2) Have you tried passing

    self      

and

    selectedPhotoDesc 

to the function

    moveToShowBottomTableView