VIPERS-CommandBus

Command bus / message bus implementation used by VIPERS. The command bus is used to implement the interactor layer in the VIPERS ios application framework.

What is a command bus ?

Have a look at this blog post (It's example is written in PHP but I think you will accept this challenge)

What is VIPER

VIPER is an application architecture for mobile app development. You can find some explanations here: [Blogpost from objc.io] (https://www.objc.io/issues/13-architecture/viper/) (It's example is written in OBJ-C but I think you will accept this as your next challenge :-P)

Usage

CommandBus

• To create a CommandHandler: Just implement the CommandHandlerProtocol. We have prepared a simple example in the example project of this pod for you.
• To use a command bus just use the CommandBus class. We have prepared a simple example in the example project of this pod for you.
• To create a command: Just use any object which you think is appropriate and which fullfils swifts Any type (As you might guess you find a simple Example in our example project)

Usage in some short lines

Create a command

struct ICommandYouToSaySomething{
    //...
}

Create a command handler for your command

import VIPERS_CommandBus_Protocol

class ExampleCommandHandler : CommandHandlerProtocol{

    // check if this handler is responsible for a given command
    func isResponsible(command: Any!) -> Bool{
        return command is ICommandYouToSaySomething
    }

    //return your result in completion
    func process<T>(command: Any!, completion: ((result: T?, error: ErrorType?) -> Void)?)  throws{

        let messageIWouldLikeToSay = "Hello World"

        completion?(result: (messageIWouldLikeToSay as! T),error:nil)
    }

}

Add your command handler to your commandBus and process your command

//create a command bus
let commandBus = CommandBus()

//add your example handler to your command bus
let commandHandler = ExampleCommandHandler()
commandBus.addHandler(commandHandler)

//create your command
let command = ICommandYouToSaySomething()

try! commandBus.process(command) { (result: String?, error: ErrorType?) in
    let message = result
    print("message: '\(message!)'")
}

FAQ

The command handler uses generics, what shall I do?

Don't be a sissy ...

Just use them, they gurantee you that swift creates an runtime exception when you choose the wrong result type.

class ExampleCommandHandler : CommandHandlerProtocol{
    // ...
    func process<T>(command: Any!, completion: ((result: T?, error: ErrorType?) -> Void)?)  throws{
        //...
        // the ' as! T' part is the important player to double check your result 
        completion?(result: (messageIWouldLikeToSay as! T),error:nil)
    }
}

If you are not used to generics you are allowed to ignore the type checking. Just implement the command handler like that:

// use the following method in your command handler
func process(command: Any!, completion: ((result: Any?, error: ErrorType?) -> Void)?) throws{

    let messageIWouldLikeToSay = "Hello World"

    completion?(result: messageIWouldLikeToSay,error:nil)

}

Requirements

iOS 8 is needed !!

Installation

VIPERS-CommandBus is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod "VIPERS-CommandBus"

Author

Jan Bartel, barteljan@yahoo.de

License

VIPERS-CommandBus is available under the MIT license. See the LICENSE file for more info.