将变量从模式表视图传递到父视图

Question

I have a detailView which has a button on it to bring up a tableView as a modal view to help the user giving a selection of names. I'm trying to figure out a simple way of passing the selected name to a textField on the parent detailView.

I have been building this project using Storyboard, but I am totally stuck at this point.

Answer 1

There are several ways to approach this kind of problem:

• shared object: The parent view controller provides some object to the child that contains the state that the child is expected to work with and possibly modify. In this case, it might be a dictionary that contains an array of names to display and the index of the selected person.

• child's properties: Often, the child view controller itself is the shared object. The parent instantiates the child, sets some of the child's properties (eg people and selectedPerson ), and presents it. When the child is finished, the parent gets the properties of the child that it cares about (eg selectedPerson ) before releasing it.

• delegation: Sometimes the child view controller will need to interact with the parent in order to do its job. This is a good time to use delegation: establish some protocol that the child knows about and the parent implements, add a delegate property to the child, and have the parent set the child's delegate property to itself before presenting it. This way, the child can talk to the parent without depending on the parent class.

For the case you describe, where you just want to convey some piece of data back to the parent when the child is done, the second strategy above is the simplest.

Answer 2

Note: DetailViewController below should be replaced with whatever the class is of your detail view controller.

1) If you don't already have a subclass of UITableViewController , create one. This will allow you to add a property to the table view controller. Change the class of your modally presented controller in your Storyboard to this new subclass.

2) Add a property to your table view controller subclass like this:

@property (weak, nonatomic) id mydelegate;

3) In prepareForSegue in your DetailViewController, set the mydelegate property of the destination view controller to self which is a pointer to your parent detailView.

4) In your DetailViewController, create a method to receive the selected name:

- (void)userDidSelectName:(NSString *)name;

5) In the tableView:didSelectRowAtIndexPath method of your tableViewController subclass, get the name from the tableViewCell and call the userDidSelectName method on the delegate:

[self.mydelegate userDidSelectName:selectedName];

6) The correct way to to this would be to define a protocol that has a method userDidSelectName and then make the delegate pointer in step 2 require a class that implements that protocol. The quicker and dirtier thing to do is to make the delegate pointer in step 2 of type DetailViewController * instead of id . This will allow you to call userDidSelectName without the compiler complaining.