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https://github.com/mbalex99/rxswiftmapviewdelegateproxyexample
Move away from Delegates into Observable APIs with RxSwift
https://github.com/mbalex99/rxswiftmapviewdelegateproxyexample
Last synced: 7 days ago
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Move away from Delegates into Observable APIs with RxSwift
- Host: GitHub
- URL: https://github.com/mbalex99/rxswiftmapviewdelegateproxyexample
- Owner: mbalex99
- Created: 2015-12-04T07:49:18.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2015-12-07T01:48:34.000Z (almost 9 years ago)
- Last Synced: 2024-04-14T18:42:23.216Z (7 months ago)
- Language: Swift
- Homepage:
- Size: 229 KB
- Stars: 39
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# RxSwiftMapViewDelegateProxyExample
This is a follow up to the Swift Meetup on RxSwift (#SLUG)
A lot of people asked me how to encapsulate delegate implementations into Rx nicely.
In other languages, you're usually forced to implement an entire class but Swift allows us
to add extensions!
This example app shows how to migrate from Delegate implementations to Rx `Observables` using `MKMapView` and `MKMapViewDelegate`
We will be turning `func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool)` method into an `Observable` property
In addition we'll add a simple `var rx_centerDidChange : Observable` extension property.
This will fire when the center changes.
We'll out put some data to the console as well as a UILabel right up top.
# The Example Source Code is Complete, but here are the steps if you want to recreate the magical experience
## Step 1 - Proxy Setup
Create a DelegateProxy class for MKMapView. This is just an Object that inherits `DelegateProxy`, `MKMapViewDelegate` and `DelegateProxyType`
```swift
import RxSwift
import RxCocoa
class RxMKMapViewDelegateProxy: DelegateProxy, MKMapViewDelegate, DelegateProxyType {
//We need a way to read the current delegate
class func currentDelegateFor(object: AnyObject) -> AnyObject? {
let mapView: MKMapView = object as! MKMapView
return mapView.delegate
}
//We need a way to set the current delegate
class func setCurrentDelegate(delegate: AnyObject?, toObject object: AnyObject) {
let mapView: MKMapView = object as! MKMapView
mapView.delegate = delegate as! MKMapViewDelegate
}
}
```
## Step 2 - Create the Extension Methods
Okay now let's create an Extension for `MKMapView` and add the methods that we want.
1. We'll need a property of `rx_delegate` which is of the type we made above.
2. Create methods that listen to the delegates respective selectors
To translate
`func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool)`
We will need to convert this function's selector into its string format. Here it is:
`"mapView:regionDidChangeAnimated:"`
The delegate proxy we made has a method called: `rx_observe` which takes a `selector string` like above and returns an `Array`
This array contains the parameters passed down from that method. You will have to cast it appropriately based off of the documentation.
The full extension code is below:
```swift
extension MKMapView {
public var rx_delegate: DelegateProxy {
return proxyForObject(self) as RxMKMapViewDelegateProxy
}
public var rx_regionDidChangeAnimated: Observable {
return rx_delegate.observe("mapView:regionDidChangeAnimated:")
.map { params in
return params[1] as! Bool
}
}
public var rx_centerDidChange: Observable {
return rx_regionDidChangeAnimated.map({ (animated) -> CLLocationCoordinate2D in
return self.centerCoordinate
})
}
}
```
## Step 3 - Listen for the Changes
Now you don't have to implement the delegate! Just observe the property right on the spot.
```swift
var mapView = MKMapView();
mapView.rx_centerDidChange
.subscribeNext{ newCenterCoord in
// so do something with it already
}
```
## Going forward
I hope this example shows you how you can leverage extensions to encapsulate Delegate listeners into consumable RxSwift Methods.
Follow this pattern and enjoy your bliss!
