What is the iOS equivalent of Android's startActivityForResult/setResult? - ios

Question

I am an Android programmer learning iOS. I have a swift view1 that calls an objective C view2. I am looking to return a String from view2 back to view 1.
In Android, we would simply view1.startActivityForResult(View2.class)
What is the iOS way to do this?

Answer 1

ViewController2.h - Objective-C
#protocol ViewController2Delegate <NSObject>
- (void)sendStringBack:(NSString *)aString;
#end
#interface ViewController2 : UIViewController
#property (nonatomic, weak) id<ViewController2Delegate> delegate;
#end
ViewController2.m - Objective-C
// When you want to send the string back and dismiss the view:
[self.delegate sendStringBack:theStringToSendBack];
ViewController1.swift - Swift
#objc class ViewController1: UIViewController, ViewController2Delegate {
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let viewContr = segue.destinationViewController as! ViewController2
viewContr.delegate = self
}
func sendStringBack(aString: String) {
let aVariable = aString
// do something with the string
// dismiss the view if you presented it modally
self.dismissViewController(self, animated: true, completion: nil)
// OR
// dismiss the view if you presented it with show/push
self.navigationController?.popViewControllerAnimated(true)
}
}

Answer 2

There is nothing like startActvityForResult() in iOS. You have to do it manually. I did it with the following process.
ViewControllerOne has a form that needed data from viewControllerTwo. ViewControllerTwo has a tableView with dataList. By tapping a data on the tableView of ViewControllerTwo it will go back to ViewControllerOne with the table data that was tapped.
Create a global variable for storing data.
var data:String = ""
Open ViewControllerTwo from ViewControllerOne with segue.
In ViewControllerTwo which has a tablewView. In didSelectRowAt method set the data to global variable and Call the method
self.navigationController?.popViewController(animated: true) like below.
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
data = dataList[indexPath.row]
self.navigationController?.popViewController(animated: true)
}
It will go back to ViewControllerOne. Now You have catch the data in viewWillAppear() or viewDidAppear() method. For example:
override func viewWillAppear(_ animated: Bool) {
if data != ""{
// Do whatever you want with this data. after doing your work set the data value to empty.
data = ""
}
}
Thats it. Happy Coding. It will work 100% sure

Answer 3

Use UIViewController+CallBack for this purpose.
Only need to set the resulting object from parent controller and child controller will override the protocol method and return any kind of object to the parent.
(id)viewUnloadWithResultObject
No ned to set the protocol
UIViewController *controller = [self.storyboard instantiateViewControllerWithIdentifier:#"NewViewController"];
[controller setResultBlock:^(id resultObject) {
NSLog(#"New View Controller did pop and resulting object is: %#", resultObject);
}];
[self.navigationController pushViewController:controller animated:YES];
You can also present the view controller and get same resulting object
UIViewController *controller = [self.storyboard instantiateViewControllerWithIdentifier:#"NewViewController"];
[controller setResultBlock:^(id resultObject) {
NSLog(#"New View Controller did dismissed and resulting object is: %#", resultObject);
}];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:controller];
[self.navigationController presentViewController:navController animated:YES completion:NULL];
Also you can have view unload call back methods. i.e.
(void)viewWillUnloadCallBack
(void)viewDidUnloadCallBack
Just inherit protocol and override these methods in your view controller to get the unload call backs.