从iphone视图传递到另一个的null值

Question

When I pass a string to another view I have a null values. My code is:

In view AddBarView.m , where I have the string:

nameAdded = nameField.text;   //nameAdded is defined as NSString in AddBarView.h
NSLog(@"namefrom addbarview: %@", nameAdded);  OK it works here , NsLog return the textfild

Now in other view AddLocationController.m

@synthesize nameAdded;
- (void)addViewControllerDidFinish:(AddBarView *)controller
{
    AddBarView *controllerAdd;
    NSLog(@"namefrom addbarview: %@", controller.nameAdded);  //here

    [self dismissModalViewControllerAnimated:YES];
}

the NSLog return a (null) value. Where is my fault?

tx in advance!

Answer 1

You need to allocate memory to nameAdded string as follows and initialize it with nameField.

nameAdded=[[NSString alloc] initWithFormat:@"%@",nameField.text];

edited Put the below line in the init method.

nameAdded=[NSString stringWithFormat:@"%@",nameField.text];

Answer 2

请参阅我的这篇文章，我在此处提供了有关如何将NSString从一个ViewController类传递到另一个iOS的教程 -将变量传递给视图控制器

Answer 3

nameAdded = nameField.text; you had only retain the value. If you edit the nameField.text later, nameAdded's value will be changed, too. you should make a copy to keep the value. nameAdded = [nameField.text copy]; Check that in AddBarView's viewDidUnload function whether you has released nameAdded or not. Otherwise, the two nameAdded variables are same object? please print their address.

Answer 4

Actually you are allocating and initializing the class that holds the textField. So it will always return you NULL value as the textField also allocated and initialized. If the class 'AddBarView' called before the class that access it, you could simply pass it to the class. Instead 'AddBarView' called after the class that access it, you may want to store the textField value in a Global String!!