ios - iOS：在视图控制器之间传递数据

Question

我正在使用 Facebook API，当用户选择一个地方（CheckIn）时，我想打开另一个视图并传递这个地方（FBGraphPlace），但是在“SecondViewController”中，当方法“viewDidLoad”被执行时，变量为空. 当用户选择地点时：

if (secondViewController == nil)
{
    SecondViewcontroller *secondViewcontroller =
    [[SecondViewcontroller alloc]
     initWithNibName:NSStringFromClass([SecondViewcontroller class])
     bundle:[NSBundle mainBundle]];

    self.secondViewcontroller = secondViewcontroller;
}

// How you reference your navigation controller will
// probably be a little different
UIBarButtonItem *newBackButton = [[UIBarButtonItem alloc] initWithTitle: @"Back" style: UIBarButtonItemStyleBordered target: nil action: nil];

[[self navigationItem] setBackBarButtonItem: newBackButton];

secondViewController.place = self.selectedPlace;

[self.navigationController
 pushViewController:self.secondViewcontroller
 animated:YES];

Answer 1

你应该先做 pushViewController，然后分配 place 变量