IKAsyncViewControllers 1.0

Maintained by Ian Keen.

You want to add pod 'IKAsyncViewControllers', '~> 1.0' similar to the following to your Podfile:

target 'MyApp' do
  pod 'IKAsyncViewControllers', '~> 1.0'
end

Then run a pod install inside your terminal, or from CocoaPods.app.

Alternatively to give it a test run, run the command:

pod try IKAsyncViewControllers

IKAsyncViewControllers 1.0

By
Ian Keen

A simple little DSL for chaing UIViewControllers together to obtain a final/single value

Why?

Whenever possible I always try and create my UIViewControllers to be just as modular as any other non-visual component. They should be able to be inserted into a 'flow' of UIViewControllers to get back some result at the end. In other words my UIViewControllers usually are dumb, they might take some input and have some output but they don't know about anything outside their function.

Example

Imagine we are creating a small contacts app, the 'flow' of that app might be something like:

Show a list of contacts
Once the user selects someone, we show a list of that contacts phone numbers
Once the user selects a phone number we dial it.

Using IKAsyncViewControllers that logic can be abstract and written as

-(void)callContact:(UINavigationController *)navController animate:(BOOL)animate {
    navController
    .push(^{ 
        return [ContactListViewController new]; 
    }, animate)
    .then(^(User *user){ 
        return [PhoneNumberViewController newWithUser:user]; 
    }, animate)
    .finally(^(NSString *phoneNumber) {
        NSString *phoneNumberString = [NSString stringWithFormat:@"tel://%@", phoneNumber];
        NSURL *url = [NSURL URLWithString:phoneNumberString];
        [[UIApplication sharedApplication] openURL:url];
    });
    return YES;
}

Usage

UIViewController

Setting up a UIViewController to support this flow is simple

.h

#import <IKAsyncViewControllers/IKAsyncViewController.h>

@interface ViewController : UIViewController <IKAsyncViewController>
@end

.m

#import "IKAsyncViewControllerOutput.h"

@interface ViewController ()
@property (nonatomic, strong) IKAsyncViewControllerOutput *output;
@end

@implementation ViewController
-(void)useOutput:(IKAsyncViewControllerOutput *)output {
    self.output = output;
}

-(IBAction)actionTriggered:(id)sender {
    [self.output output:<output_value>];
}
@end

Beginning the chain

Starting a chain of IKAsyncViewControllers is easy using the UINavigationController category methods. Given a method to create the first view controller you want to show

-(UIViewController<IKAsyncViewController> *)firstViewController { ... }

You can make it the root view controller using the root block

-(void)startChain:(UINavigationController *)navController animate:(BOOL)animate {
    navController.root(^{ return [self firstViewController]; }, animate);
}

Or you can just push it onto an existing stack with the push block

-(void)startChain:(UINavigationController *)navController animate:(BOOL)animate {
    navController.push(^{ return [self firstViewController]; }, animate);
}

Continuing the chain

Parsing a value from one IKAsyncViewController to the next is also simple. Given methods to create an IKAsyncViewController that take some input and produce some output

-(UIViewController<IKAsyncViewController> *)anotherViewController:(id)input { ... }
-(UIViewController<IKAsyncViewController> *)andAnotherViewController:(id)input { ... }

You using the then block

-(void)startChain:(UINavigationController *)navController animate:(BOOL)animate {
    navController.root(^{ return [self firstViewController]; }, animate)
    .then(^(id output) { return [self anotherViewController:output]; }, animate)
    .then(^(id output) { return [self andAnotherViewController:output]; }, animate);
}

Or using the thenIf block to conditionally show an IKAsyncViewController. If the predicate is NO the IKAsyncViewController will be skipped in the chain

-(void)startChain:(UINavigationController *)navController {
    navController.root(^{ return [self firstViewController]; })
    .thenIf([self shouldShowAnother], ^(id output) { return [self anotherViewController:output]; }, animate)
    .then(^(id output) { return [self andAnotherViewController:output]; }, animate);
}
-(BOOL)shouldShowAnother { ... }

Completing a chain

Eventually the idea is to get some final value from a chain of IKAsyncViewControllers this is achieved with the finally block

-(void)startChain:(UINavigationController *)navController {
    navController.root(^{ return [self firstViewController]; })
    .thenIf([self shouldShowAnother], ^(id output) { return [self anotherViewController:output]; }, animate)
    .then(^(id output) { return [self andAnotherViewController:output]; }, animate)
    .finally(^(id finalValue) {
        //.. do something with finalValue
    });
}
-(BOOL)shouldShowAnother { ... }

What IKAsyncViewControllers is..

IKAsyncViewControllers is a nice, simple DSL that can help you think about making your UIViewControllers more modular. It is a great tool you can use when you have a clearly defined set of UIViewControllers that you can chain together to get some output.

What IKAsyncViewControllers is not..

IKAsyncViewControllers is not a replacement for storyboards and while it can be used for complex/multi branch navigation that doesn't necessarily make it the right tool for the job. Have a good think about wether IKAsyncViewControllers is right for your app.

Installation

or manually by adding the source files from the IKEvents subfolder to your project

The rest..

Pull Requests are welcome!

If you use this in a project I would love to hear about it!..

Contact

I'm usually hanging out on iOS Developers. You should check them out!